Chapter 21 INFORMATION_SCHEMA Tables

Table of Contents

21.1 Introduction
21.2 The INFORMATION_SCHEMA CHARACTER_SETS Table
21.3 The INFORMATION_SCHEMA COLLATIONS Table
21.4 The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table
21.5 The INFORMATION_SCHEMA COLUMNS Table
21.6 The INFORMATION_SCHEMA COLUMN_PRIVILEGES Table
21.7 The INFORMATION_SCHEMA ENGINES Table
21.8 The INFORMATION_SCHEMA EVENTS Table
21.9 The INFORMATION_SCHEMA GLOBAL_STATUS and SESSION_STATUS Tables
21.10 The INFORMATION_SCHEMA GLOBAL_VARIABLES and SESSION_VARIABLES Tables
21.11 The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table
21.12 The INFORMATION_SCHEMA OPTIMIZER_TRACE Table
21.13 The INFORMATION_SCHEMA PARAMETERS Table
21.14 The INFORMATION_SCHEMA PARTITIONS Table
21.15 The INFORMATION_SCHEMA PLUGINS Table
21.16 The INFORMATION_SCHEMA PROCESSLIST Table
21.17 The INFORMATION_SCHEMA PROFILING Table
21.18 The INFORMATION_SCHEMA REFERENTIAL_CONSTRAINTS Table
21.19 The INFORMATION_SCHEMA ROUTINES Table
21.20 The INFORMATION_SCHEMA SCHEMATA Table
21.21 The INFORMATION_SCHEMA SCHEMA_PRIVILEGES Table
21.22 The INFORMATION_SCHEMA STATISTICS Table
21.23 The INFORMATION_SCHEMA TABLES Table
21.24 The INFORMATION_SCHEMA TABLESPACES Table
21.25 The INFORMATION_SCHEMA TABLE_CONSTRAINTS Table
21.26 The INFORMATION_SCHEMA TABLE_PRIVILEGES Table
21.27 The INFORMATION_SCHEMA TRIGGERS Table
21.28 The INFORMATION_SCHEMA USER_PRIVILEGES Table
21.29 The INFORMATION_SCHEMA VIEWS Table
21.30 INFORMATION_SCHEMA InnoDB Tables
21.30.1 The INFORMATION_SCHEMA INNODB_BUFFER_PAGE Table
21.30.2 The INFORMATION_SCHEMA INNODB_BUFFER_PAGE_LRU Table
21.30.3 The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table
21.30.4 The INFORMATION_SCHEMA INNODB_CMP and INNODB_CMP_RESET Tables
21.30.5 The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables
21.30.6 The INFORMATION_SCHEMA INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET Tables
21.30.7 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table
21.30.8 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table
21.30.9 The INFORMATION_SCHEMA INNODB_FT_DEFAULT_STOPWORD Table
21.30.10 The INFORMATION_SCHEMA INNODB_FT_DELETED Table
21.30.11 The INFORMATION_SCHEMA INNODB_FT_INDEX_CACHE Table
21.30.12 The INFORMATION_SCHEMA INNODB_FT_INDEX_TABLE Table
21.30.13 The INFORMATION_SCHEMA INNODB_LOCKS Table
21.30.14 The INFORMATION_SCHEMA INNODB_LOCK_WAITS Table
21.30.15 The INFORMATION_SCHEMA INNODB_METRICS Table
21.30.16 The INFORMATION_SCHEMA INNODB_SYS_COLUMNS Table
21.30.17 The INFORMATION_SCHEMA INNODB_SYS_DATAFILES Table
21.30.18 The INFORMATION_SCHEMA INNODB_SYS_FIELDS Table
21.30.19 The INFORMATION_SCHEMA INNODB_SYS_FOREIGN Table
21.30.20 The INFORMATION_SCHEMA INNODB_SYS_FOREIGN_COLS Table
21.30.21 The INFORMATION_SCHEMA INNODB_SYS_INDEXES Table
21.30.22 The INFORMATION_SCHEMA INNODB_SYS_TABLES Table
21.30.23 The INFORMATION_SCHEMA INNODB_SYS_TABLESPACES Table
21.30.24 The INFORMATION_SCHEMA INNODB_SYS_TABLESTATS View
21.30.25 The INFORMATION_SCHEMA INNODB_TRX Table
21.31 INFORMATION_SCHEMA NDB Cluster Tables
21.31.1 The INFORMATION_SCHEMA FILES Table
21.31.2 The INFORMATION_SCHEMA ndb_transid_mysql_connection_map Table
21.32 INFORMATION_SCHEMA Thread Pool Tables
21.32.1 The INFORMATION_SCHEMA TP_THREAD_GROUP_STATE Table
21.32.2 The INFORMATION_SCHEMA TP_THREAD_GROUP_STATS Table
21.32.3 The INFORMATION_SCHEMA TP_THREAD_STATE Table
21.33 INFORMATION_SCHEMA Connection-Control Tables
21.33.1 The INFORMATION_SCHEMA CONNECTION_CONTROL_FAILED_LOGIN_ATTEMPTS Table
21.34 Extensions to SHOW Statements

INFORMATION_SCHEMA provides access to database metadata, information about the MySQL server such as the name of a database or table, the data type of a column, or access privileges. Other terms that are sometimes used for this information are data dictionary and system catalog.

21.1 Introduction

INFORMATION_SCHEMA provides access to database metadata, information about the MySQL server such as the name of a database or table, the data type of a column, or access privileges. Other terms that are sometimes used for this information are data dictionary and system catalog.

INFORMATION_SCHEMA Usage Notes

INFORMATION_SCHEMA is a database within each MySQL instance, the place that stores information about all the other databases that the MySQL server maintains. The INFORMATION_SCHEMA database contains several read-only tables. They are actually views, not base tables, so there are no files associated with them, and you cannot set triggers on them. Also, there is no database directory with that name.

Although you can select INFORMATION_SCHEMA as the default database with a USE statement, you can only read the contents of tables, not perform INSERT, UPDATE, or DELETE operations on them.

Here is an example of a statement that retrieves information from INFORMATION_SCHEMA:

mysql> SELECT table_name, table_type, engine
       FROM information_schema.tables
       WHERE table_schema = 'db5'
       ORDER BY table_name;
+------------+------------+--------+
| table_name | table_type | engine |
+------------+------------+--------+
| fk         | BASE TABLE | InnoDB |
| fk2        | BASE TABLE | InnoDB |
| goto       | BASE TABLE | MyISAM |
| into       | BASE TABLE | MyISAM |
| k          | BASE TABLE | MyISAM |
| kurs       | BASE TABLE | MyISAM |
| loop       | BASE TABLE | MyISAM |
| pk         | BASE TABLE | InnoDB |
| t          | BASE TABLE | MyISAM |
| t2         | BASE TABLE | MyISAM |
| t3         | BASE TABLE | MyISAM |
| t7         | BASE TABLE | MyISAM |
| tables     | BASE TABLE | MyISAM |
| v          | VIEW       | NULL   |
| v2         | VIEW       | NULL   |
| v3         | VIEW       | NULL   |
| v56        | VIEW       | NULL   |
+------------+------------+--------+
17 rows in set (0.01 sec)

Explanation: The statement requests a list of all the tables in database db5, showing just three pieces of information: the name of the table, its type, and its storage engine.

Character Set Considerations

The definition for character columns (for example, TABLES.TABLE_NAME) is generally VARCHAR(N) CHARACTER SET utf8 where N is at least 64. MySQL uses the default collation for this character set (utf8_general_ci) for all searches, sorts, comparisons, and other string operations on such columns.

Because some MySQL objects are represented as files, searches in INFORMATION_SCHEMA string columns can be affected by file system case sensitivity. For more information, see Section 10.8.7, “Using Collation in INFORMATION_SCHEMA Searches”.

INFORMATION_SCHEMA as Alternative to SHOW Statements

The SELECT ... FROM INFORMATION_SCHEMA statement is intended as a more consistent way to provide access to the information provided by the various SHOW statements that MySQL supports (SHOW DATABASES, SHOW TABLES, and so forth). Using SELECT has these advantages, compared to SHOW:

  • It conforms to Codd's rules, because all access is done on tables.

  • You can use the familiar syntax of the SELECT statement, and only need to learn some table and column names.

  • The implementor need not worry about adding keywords.

  • You can filter, sort, concatenate, and transform the results from INFORMATION_SCHEMA queries into whatever format your application needs, such as a data structure or a text representation to parse.

  • This technique is more interoperable with other database systems. For example, Oracle Database users are familiar with querying tables in the Oracle data dictionary.

Because SHOW is familiar and widely used, the SHOW statements remain as an alternative. In fact, along with the implementation of INFORMATION_SCHEMA, there are enhancements to SHOW as described in Section 21.34, “Extensions to SHOW Statements”.

INFORMATION_SCHEMA and Privileges

Each MySQL user has the right to access these tables, but can see only the rows in the tables that correspond to objects for which the user has the proper access privileges. In some cases (for example, the ROUTINE_DEFINITION column in the INFORMATION_SCHEMA ROUTINES table), users who have insufficient privileges see NULL. These restrictions do not apply for InnoDB tables; you can see them with only the PROCESS privilege.

The same privileges apply to selecting information from INFORMATION_SCHEMA and viewing the same information through SHOW statements. In either case, you must have some privilege on an object to see information about it.

Performance Considerations

INFORMATION_SCHEMA queries that search for information from more than one database might take a long time and impact performance. To check the efficiency of a query, you can use EXPLAIN. For information about using EXPLAIN output to tune INFORMATION_SCHEMA queries, see Section 8.2.3, “Optimizing INFORMATION_SCHEMA Queries”.

Standards Considerations

The implementation for the INFORMATION_SCHEMA table structures in MySQL follows the ANSI/ISO SQL:2003 standard Part 11 Schemata. Our intent is approximate compliance with SQL:2003 core feature F021 Basic information schema.

Users of SQL Server 2000 (which also follows the standard) may notice a strong similarity. However, MySQL has omitted many columns that are not relevant for our implementation, and added columns that are MySQL-specific. One such added column is the ENGINE column in the INFORMATION_SCHEMA TABLES table.

Although other DBMSs use a variety of names, like syscat or system, the standard name is INFORMATION_SCHEMA.

To avoid using any name that is reserved in the standard or in DB2, SQL Server, or Oracle, we changed the names of some columns marked MySQL extension. (For example, we changed COLLATION to TABLE_COLLATION in the TABLES table.) See the list of reserved words near the end of this article: https://web.archive.org/web/20070428032454/http://www.dbazine.com/db2/db2-disarticles/gulutzan5.

Conventions in the INFORMATION_SCHEMA Reference Sections

The following sections describe each of the tables and columns in INFORMATION_SCHEMA. For each column, there are three pieces of information:

  • INFORMATION_SCHEMA Name indicates the name for the column in the INFORMATION_SCHEMA table. This corresponds to the standard SQL name unless the Remarks field says MySQL extension.

  • SHOW Name indicates the equivalent field name in the closest SHOW statement, if there is one.

  • Remarks provides additional information where applicable. If this field is NULL, it means that the value of the column is always NULL. If this field says MySQL extension, the column is a MySQL extension to standard SQL.

Many sections indicate what SHOW statement is equivalent to a SELECT that retrieves information from INFORMATION_SCHEMA. For SHOW statements that display information for the default database if you omit a FROM db_name clause, you can often select information for the default database by adding an AND TABLE_SCHEMA = SCHEMA() condition to the WHERE clause of a query that retrieves information from an INFORMATION_SCHEMA table.

Related Information

These sections discuss additional INFORMATION_SCHEMA-related topics:

21.2 The INFORMATION_SCHEMA CHARACTER_SETS Table

The CHARACTER_SETS table provides information about available character sets.

The CHARACTER_SETS table has these columns:

  • CHARACTER_SET_NAME

    The character set name.

  • DEFAULT_COLLATE_NAME

    The default collation for the character set.

  • DESCRIPTION

    A description of the character set.

  • MAXLEN

    The maximum number of bytes required to store one character.

Notes

Character set information is also available from the SHOW CHARACTER SET statement. See Section 13.7.5.4, “SHOW CHARACTER SET Syntax”. The following statements are equivalent:

SELECT * FROM INFORMATION_SCHEMA.CHARACTER_SETS
  [WHERE CHARACTER_SET_NAME LIKE 'wild']

SHOW CHARACTER SET
  [LIKE 'wild']

21.3 The INFORMATION_SCHEMA COLLATIONS Table

The COLLATIONS table provides information about collations for each character set.

The COLLATIONS table has these columns:

  • COLLATION_NAME

    The collation name.

  • CHARACTER_SET_NAME

    The name of the character set with which the collation is associated.

  • ID

    The collation ID.

  • IS_DEFAULT

    Whether the collation is the default for its character set.

  • IS_COMPILED

    Whether the character set is compiled into the server.

  • SORTLEN

    This is related to the amount of memory required to sort strings expressed in the character set.

Notes

Collation information is also available from the SHOW COLLATION statement. See Section 13.7.5.5, “SHOW COLLATION Syntax”. The following statements are equivalent:

SELECT COLLATION_NAME FROM INFORMATION_SCHEMA.COLLATIONS
  [WHERE COLLATION_NAME LIKE 'wild']

SHOW COLLATION
  [LIKE 'wild']

21.4 The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table

The COLLATION_CHARACTER_SET_APPLICABILITY table indicates what character set is applicable for what collation.

The COLLATION_CHARACTER_SET_APPLICABILITY table has these columns:

  • COLLATION_NAME

    The collation name.

  • CHARACTER_SET_NAME

    The name of the character set with which the collation is associated.

Notes

The COLLATION_CHARACTER_SET_APPLICABILITY columns are equivalent to the first two columns displayed by the SHOW COLLATION statement.

21.5 The INFORMATION_SCHEMA COLUMNS Table

The COLUMNS table provides information about columns in tables.

The COLUMNS table has these columns:

  • TABLE_CATALOG

    The name of the catalog to which the table containing the column belongs. This value is always def.

  • TABLE_SCHEMA

    The name of the schema (database) to which the table containing the column belongs.

  • TABLE_NAME

    The name of the table containing the column.

  • COLUMN_NAME

    The name of the column.

  • ORDINAL_POSITION

    The position of the column within the table. ORDINAL_POSITION is necessary because you might want to say ORDER BY ORDINAL_POSITION. Unlike SHOW COLUMNS, SELECT from the COLUMNS table does not have automatic ordering.

  • COLUMN_DEFAULT

    The default value for the column. This is NULL if the column has an explicit default of NULL, or if the column definition includes no DEFAULT clause.

  • IS_NULLABLE

    The column nullability. The value is YES if NULL values can be stored in the column, NO if not.

  • DATA_TYPE

    The column data type.

    The DATA_TYPE value is the type name only with no other information. The COLUMN_TYPE value contains the type name and possibly other information such as the precision or length.

  • CHARACTER_MAXIMUM_LENGTH

    For string columns, the maximum length in characters.

  • CHARACTER_OCTET_LENGTH

    For string columns, the maximum length in bytes.

  • NUMERIC_PRECISION

    For numeric columns, the numeric precision.

  • NUMERIC_SCALE

    For numeric columns, the numeric scale.

  • DATETIME_PRECISION

    For temporal columns, the fractional seconds precision.

  • CHARACTER_SET_NAME

    For character string columns, the character set name.

  • COLLATION_NAME

    For character string columns, the collation name.

  • COLUMN_TYPE

    The column data type.

    The DATA_TYPE value is the type name only with no other information. The COLUMN_TYPE value contains the type name and possibly other information such as the precision or length.

  • COLUMN_KEY

    Whether the column is indexed:

    • If COLUMN_KEY is empty, the column either is not indexed or is indexed only as a secondary column in a multiple-column, nonunique index.

    • If COLUMN_KEY is PRI, the column is a PRIMARY KEY or is one of the columns in a multiple-column PRIMARY KEY.

    • If COLUMN_KEY is UNI, the column is the first column of a UNIQUE index. (A UNIQUE index permits multiple NULL values, but you can tell whether the column permits NULL by checking the Null column.)

    • If COLUMN_KEY is MUL, the column is the first column of a nonunique index in which multiple occurrences of a given value are permitted within the column.

    If more than one of the COLUMN_KEY values applies to a given column of a table, COLUMN_KEY displays the one with the highest priority, in the order PRI, UNI, MUL.

    A UNIQUE index may be displayed as PRI if it cannot contain NULL values and there is no PRIMARY KEY in the table. A UNIQUE index may display as MUL if several columns form a composite UNIQUE index; although the combination of the columns is unique, each column can still hold multiple occurrences of a given value.

  • EXTRA

    Any additional information that is available about a given column. The value is nonempty in these cases: auto_increment for columns that have the AUTO_INCREMENT attribute; on update CURRENT_TIMESTAMP for TIMESTAMP or DATETIME columns that have the ON UPDATE CURRENT_TIMESTAMP attribute.

  • PRIVILEGES

    The privileges you have for the column.

  • COLUMN_COMMENT

    Any comment included in the column definition.

Notes

  • In SHOW COLUMNS, the Type display includes values from several different COLUMNS columns.

  • CHARACTER_OCTET_LENGTH should be the same as CHARACTER_MAXIMUM_LENGTH, except for multibyte character sets.

  • CHARACTER_SET_NAME can be derived from COLLATION_NAME. For example, if you say SHOW FULL COLUMNS FROM t, and you see in the COLLATION_NAME column a value of latin1_swedish_ci, the character set is what is before the first underscore: latin1.

Column information is also available from the SHOW COLUMNS statement. See Section 13.7.5.6, “SHOW COLUMNS Syntax”. The following statements are nearly equivalent:

SELECT COLUMN_NAME, DATA_TYPE, IS_NULLABLE, COLUMN_DEFAULT
  FROM INFORMATION_SCHEMA.COLUMNS
  WHERE table_name = 'tbl_name'
  [AND table_schema = 'db_name']
  [AND column_name LIKE 'wild']

SHOW COLUMNS
  FROM tbl_name
  [FROM db_name]
  [LIKE 'wild']

21.6 The INFORMATION_SCHEMA COLUMN_PRIVILEGES Table

The COLUMN_PRIVILEGES table provides information about column privileges. It takes its values from the mysql.columns_priv system table.

The COLUMN_PRIVILEGES table has these columns:

  • GRANTEE

    The name of the account to which the privilege is granted, in 'user_name'@'host_name' format.

  • TABLE_CATALOG

    The name of the catalog to which the table containing the column belongs. This value is always def.

  • TABLE_SCHEMA

    The name of the schema (database) to which the table containing the column belongs.

  • TABLE_NAME

    The name of the table containing the column.

  • COLUMN_NAME

    The name of the column.

  • PRIVILEGE_TYPE

    The privilege granted. The value can be any privilege that can be granted at the column level; see Section 13.7.1.4, “GRANT Syntax”. Each row lists a single privilege, so there is one row per column privilege held by the grantee.

    In the output from SHOW FULL COLUMNS, the privileges are all in one column and in lowercase, for example, select,insert,update,references. In COLUMN_PRIVILEGES, there is one privilege per row, in uppercase.

  • IS_GRANTABLE

    YES if the user has the GRANT OPTION privilege, NO otherwise. The output does not list GRANT OPTION as a separate row with PRIVILEGE_TYPE='GRANT OPTION'.

Notes

The following statements are not equivalent:

SELECT ... FROM INFORMATION_SCHEMA.COLUMN_PRIVILEGES

SHOW GRANTS ...

21.7 The INFORMATION_SCHEMA ENGINES Table

The ENGINES table provides information about storage engines. This is particularly useful for checking whether a storage engine is supported, or to see what the default engine is.

The ENGINES table has these columns:

  • ENGINE

    The name of the storage engine.

  • SUPPORT

    The server's level of support for the storage engine, as shown in the following table.

    Value Meaning
    YES The engine is supported and is active
    DEFAULT Like YES, plus this is the default engine
    NO The engine is not supported
    DISABLED The engine is supported but has been disabled

    A value of NO means that the server was compiled without support for the engine, so it cannot be enabled at runtime.

    A value of DISABLED occurs either because the server was started with an option that disables the engine, or because not all options required to enable it were given. In the latter case, the error log should contain a reason indicating why the option is disabled. See Section 5.4.2, “The Error Log”.

    You might also see DISABLED for a storage engine if the server was compiled to support it, but was started with a --skip-engine_name option. For the NDB storage engine, DISABLED means the server was compiled with support for NDB Cluster, but was not started with the --ndbcluster option.

    All MySQL servers support MyISAM tables. It is not possible to disable MyISAM.

  • COMMENT

    A brief description of the storage engine.

  • TRANSACTIONS

    Whether the storage engine supports transactions.

  • XA

    Whether the storage engine supports XA transactions.

  • SAVEPOINTS

    Whether the storage engine supports savepoints.

Notes

  • The ENGINES table is a nonstandard INFORMATION_SCHEMA table.

Storage engine information is also available from the SHOW ENGINES statement. See Section 13.7.5.17, “SHOW ENGINES Syntax”. The following statements are equivalent:

SELECT * FROM INFORMATION_SCHEMA.ENGINES

SHOW ENGINES

21.8 The INFORMATION_SCHEMA EVENTS Table

The EVENTS table provides information about Event Manager events, which are discussed in Section 20.4, “Using the Event Scheduler”.

The EVENTS table has these columns:

  • EVENT_CATALOG

    The name of the catalog to which the event belongs. This value is always def.

  • EVENT_SCHEMA

    The name of the schema (database) to which the event belongs.

  • EVENT_NAME

    The name of the event.

  • DEFINER

    The account of the user who created the event, in 'user_name'@'host_name' format.

  • TIME_ZONE

    The event time zone, which is the time zone used for scheduling the event and that is in effect within the event as it executes. The default value is SYSTEM.

  • EVENT_BODY

    The language used for the statements in the event's DO clause. The value is always SQL.

  • EVENT_DEFINITION

    The text of the SQL statement making up the event's DO clause; in other words, the statement executed by this event.

  • EVENT_TYPE

    The event repetition type, either ONE TIME (transient) or RECURRING (repeating).

  • EXECUTE_AT

    For a one-time event, this is the DATETIME value specified in the AT clause of the CREATE EVENT statement used to create the event, or of the last ALTER EVENT statement that modified the event. The value shown in this column reflects the addition or subtraction of any INTERVAL value included in the event's AT clause. For example, if an event is created using ON SCHEDULE AT CURRENT_TIMESTAMP + '1:6' DAY_HOUR, and the event was created at 2018-02-09 14:05:30, the value shown in this column would be '2018-02-10 20:05:30'. If the event's timing is determined by an EVERY clause instead of an AT clause (that is, if the event is recurring), the value of this column is NULL.

  • INTERVAL_VALUE

    For a recurring event, the number of intervals to wait between event executions. For a transient event, the value is always NULL.

  • INTERVAL_FIELD

    The time units used for the interval which a recurring event waits before repeating. For a transient event, the value is always NULL.

  • SQL_MODE

    The SQL mode in effect when the event was created or altered, and under which the event executes. For the permitted values, see Section 5.1.10, “Server SQL Modes”.

  • STARTS

    The start date and time for a recurring event. This is displayed as a DATETIME value, and is NULL if no start date and time are defined for the event. For a transient event, this column is always NULL. For a recurring event whose definition includes a STARTS clause, this column contains the corresponding DATETIME value. As with the EXECUTE_AT column, this value resolves any expressions used. If there is no STARTS clause affecting the timing of the event, this column is NULL

  • ENDS

    For a recurring event whose definition includes a ENDS clause, this column contains the corresponding DATETIME value. As with the EXECUTE_AT column, this value resolves any expressions used. If there is no ENDS clause affecting the timing of the event, this column is NULL.

  • STATUS

    The event status. One of ENABLED, DISABLED, or SLAVESIDE_DISABLED. SLAVESIDE_DISABLED indicates that the creation of the event occurred on another MySQL server acting as a replication master and replicated to the current MySQL server which is acting as a slave, but the event is not presently being executed on the slave. For more information, see Section 17.4.1.16, “Replication of Invoked Features”. information.

  • ON_COMPLETION

    One of the two values PRESERVE or NOT PRESERVE.

  • CREATED

    The date and time when the event was created. This is a TIMESTAMP value.

  • LAST_ALTERED

    The date and time when the event was last modified. This is a TIMESTAMP value. If the event has not been modified since its creation, this value is the same as the CREATED value.

  • LAST_EXECUTED

    The date and time when the event last executed. This is a DATETIME value. If the event has never executed, this column is NULL.

    LAST_EXECUTED indicates when the event started. As a result, the ENDS column is never less than LAST_EXECUTED.

  • EVENT_COMMENT

    The text of the comment, if the event has one. If not, this value is empty.

  • ORIGINATOR

    The server ID of the MySQL server on which the event was created; used in replication. The default value is 0.

  • CHARACTER_SET_CLIENT

    The session value of the character_set_client system variable when the event was created.

  • COLLATION_CONNECTION

    The session value of the collation_connection system variable when the event was created.

  • DATABASE_COLLATION

    The collation of the database with which the event is associated.

Notes

Example

Suppose that the user 'jon'@'ghidora' creates an event named e_daily, and then modifies it a few minutes later using an ALTER EVENT statement, as shown here:

DELIMITER |

CREATE EVENT e_daily
    ON SCHEDULE
      EVERY 1 DAY
    COMMENT 'Saves total number of sessions then clears the table each day'
    DO
      BEGIN
        INSERT INTO site_activity.totals (time, total)
          SELECT CURRENT_TIMESTAMP, COUNT(*)
            FROM site_activity.sessions;
        DELETE FROM site_activity.sessions;
      END |

DELIMITER ;

ALTER EVENT e_daily
    ENABLE;

(Note that comments can span multiple lines.)

This user can then run the following SELECT statement, and obtain the output shown:

mysql> SELECT * FROM INFORMATION_SCHEMA.EVENTS
       WHERE EVENT_NAME = 'e_daily'
       AND EVENT_SCHEMA = 'myschema'\G
*************************** 1. row ***************************
       EVENT_CATALOG: def
        EVENT_SCHEMA: myschema
          EVENT_NAME: e_daily
             DEFINER: jon@ghidora
           TIME_ZONE: SYSTEM
          EVENT_BODY: SQL
    EVENT_DEFINITION: BEGIN
        INSERT INTO site_activity.totals (time, total)
          SELECT CURRENT_TIMESTAMP, COUNT(*)
            FROM site_activity.sessions;
        DELETE FROM site_activity.sessions;
      END
          EVENT_TYPE: RECURRING
          EXECUTE_AT: NULL
      INTERVAL_VALUE: 1
      INTERVAL_FIELD: DAY
            SQL_MODE: NO_ENGINE_SUBSTITUTION
              STARTS: 2018-08-08 11:06:34
                ENDS: NULL
              STATUS: ENABLED
       ON_COMPLETION: NOT PRESERVE
             CREATED: 2018-08-08 11:06:34
        LAST_ALTERED: 2018-08-08 11:06:34
       LAST_EXECUTED: 2018-08-08 16:06:34
       EVENT_COMMENT: Saves total number of sessions then clears the
                      table each day
          ORIGINATOR: 1
CHARACTER_SET_CLIENT: utf8
COLLATION_CONNECTION: utf8_general_ci
  DATABASE_COLLATION: latin1_swedish_ci

Event information is also available from the SHOW EVENTS statement. See Section 13.7.5.19, “SHOW EVENTS Syntax”. The following statements are equivalent:

SELECT
    EVENT_SCHEMA, EVENT_NAME, DEFINER, TIME_ZONE, EVENT_TYPE, EXECUTE_AT,
    INTERVAL_VALUE, INTERVAL_FIELD, STARTS, ENDS, STATUS, ORIGINATOR,
    CHARACTER_SET_CLIENT, COLLATION_CONNECTION, DATABASE_COLLATION
  FROM INFORMATION_SCHEMA.EVENTS
  WHERE table_schema = 'db_name'
  [AND column_name LIKE 'wild']

SHOW EVENTS
  [FROM db_name]
  [LIKE 'wild']

21.9 The INFORMATION_SCHEMA GLOBAL_STATUS and SESSION_STATUS Tables

The GLOBAL_STATUS and SESSION_STATUS tables provide information about server status variables. Their contents correspond to the information produced by the SHOW GLOBAL STATUS and SHOW SESSION STATUS statements (see Section 13.7.5.36, “SHOW STATUS Syntax”).

Notes

  • The VARIABLE_VALUE column for each of these tables is defined as VARCHAR(1024).

21.10 The INFORMATION_SCHEMA GLOBAL_VARIABLES and SESSION_VARIABLES Tables

The GLOBAL_VARIABLES and SESSION_VARIABLES tables provide information about server status variables. Their contents correspond to the information produced by the SHOW GLOBAL VARIABLES and SHOW SESSION VARIABLES statements (see Section 13.7.5.40, “SHOW VARIABLES Syntax”).

Notes

  • The VARIABLE_VALUE column for each of these tables is defined as VARCHAR(1024). For variables with very long values that are not completely displayed, use SELECT as a workaround. For example:

    SELECT @@GLOBAL.innodb_data_file_path;
    

21.11 The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table

The KEY_COLUMN_USAGE table describes which key columns have constraints.

The KEY_COLUMN_USAGE table has these columns:

  • CONSTRAINT_CATALOG

    The name of the catalog to which the constraint belongs. This value is always def.

  • CONSTRAINT_SCHEMA

    The name of the schema (database) to which the constraint belongs.

  • CONSTRAINT_NAME

    The name of the constraint.

  • TABLE_CATALOG

    The name of the catalog to which the table belongs. This value is always def.

  • TABLE_SCHEMA

    The name of the schema (database) to which the table belongs.

  • TABLE_NAME

    The name of the table that has the constraint.

  • COLUMN_NAME

    The name of the column that has the constraint.

    If the constraint is a foreign key, then this is the column of the foreign key, not the column that the foreign key references.

  • ORDINAL_POSITION

    The column's position within the constraint, not the column's position within the table. Column positions are numbered beginning with 1.

  • POSITION_IN_UNIQUE_CONSTRAINT

    NULL for unique and primary-key constraints. For foreign-key constraints, this column is the ordinal position in key of the table that is being referenced.

  • REFERENCED_TABLE_SCHEMA

    The name of the schema (database) referenced by the constraint.

  • REFERENCED_TABLE_NAME

    The name of the table referenced by the constraint.

  • REFERENCED_COLUMN_NAME

    The name of the column referenced by the constraint.

Suppose that there are two tables name t1 and t3 that have the following definitions:

CREATE TABLE t1
(
    s1 INT,
    s2 INT,
    s3 INT,
    PRIMARY KEY(s3)
) ENGINE=InnoDB;

CREATE TABLE t3
(
    s1 INT,
    s2 INT,
    s3 INT,
    KEY(s1),
    CONSTRAINT CO FOREIGN KEY (s2) REFERENCES t1(s3)
) ENGINE=InnoDB;

For those two tables, the KEY_COLUMN_USAGE table has two rows:

  • One row with CONSTRAINT_NAME = 'PRIMARY', TABLE_NAME = 't1', COLUMN_NAME = 's3', ORDINAL_POSITION = 1, POSITION_IN_UNIQUE_CONSTRAINT = NULL.

  • One row with CONSTRAINT_NAME = 'CO', TABLE_NAME = 't3', COLUMN_NAME = 's2', ORDINAL_POSITION = 1, POSITION_IN_UNIQUE_CONSTRAINT = 1.

21.12 The INFORMATION_SCHEMA OPTIMIZER_TRACE Table

The OPTIMIZER_TRACE table provides information produced by the optimizer tracing capability for traced statements. To enable tracking, use the optimizer_trace system variable. For details, see MySQL Internals: Tracing the Optimizer.

The OPTIMIZER_TRACE table has these columns:

  • QUERY

    The text of the traced statement.

  • TRACE

    The trace, in JSON format.

  • MISSING_BYTES_BEYOND_MAX_MEM_SIZE

    Each remembered trace is a string that is extended as optimization progresses and appends data to it. The optimizer_trace_max_mem_size variable sets a limit on the total amount of memory used by all currently remembered traces. If this limit is reached, the current trace is not extended (and thus is incomplete), and the MISSING_BYTES_BEYOND_MAX_MEM_SIZE column shows the number of bytes missing from the trace.

  • INSUFFICIENT_PRIVILEGES

    If a traced query uses views or stored routines that have SQL SECURITY with a value of DEFINER, it may be that a user other than the definer is denied from seeing the trace of the query. In that case, the trace is shown as empty and INSUFFICIENT_PRIVILEGES has a value of 1. Otherwise, the value is 0.

21.13 The INFORMATION_SCHEMA PARAMETERS Table

The PARAMETERS table provides information about parameters for stored routines (stored procedures and stored functions), and about return values for stored functions. The PARAMETERS table does not include built-in SQL functions or user-defined functions (UDFs). Parameter information is similar to the contents of the param_list column in the mysql.proc table.

The PARAMETERS table has these columns:

  • SPECIFIC_CATALOG

    The name of the catalog to which the routine containing the parameter belongs. This value is always def.

  • SPECIFIC_SCHEMA

    The name of the schema (database) to which the routine containing the parameter belongs.

  • SPECIFIC_NAME

    The name of the routine containing the parameter.

  • ORDINAL_POSITION

    For successive parameters of a stored procedure or function, the ORDINAL_POSITION values are 1, 2, 3, and so forth. For a stored function, there is also a row that applies to the function return value (as described by the RETURNS clause). The return value is not a true parameter, so the row that describes it has these unique characteristics:

    • The ORDINAL_POSITION value is 0.

    • The PARAMETER_NAME and PARAMETER_MODE values are NULL because the return value has no name and the mode does not apply.

  • PARAMETER_MODE

    The mode of the parameter. This value is one of IN, OUT, or INOUT. For a stored function return value, this value is NULL.

  • PARAMETER_NAME

    The name of the parameter. For a stored function return value, this value is NULL.

  • DATA_TYPE

    The parameter data type.

    The DATA_TYPE value is the type name only with no other information. The DTD_IDENTIFIER value contains the type name and possibly other information such as the precision or length.

  • CHARACTER_MAXIMUM_LENGTH

    For string parameters, the maximum length in characters.

  • CHARACTER_OCTET_LENGTH

    For string parameters, the maximum length in bytes.

  • NUMERIC_PRECISION

    For numeric parameters, the numeric precision.

  • NUMERIC_SCALE

    For numeric parameters, the numeric scale.

  • DATETIME_PRECISION

    For temporal parameters, the fractional seconds precision.

  • CHARACTER_SET_NAME

    For character string parameters, the character set name.

  • COLLATION_NAME

    For character string parameters, the collation name.

  • DTD_IDENTIFIER

    The parameter data type.

    The DATA_TYPE value is the type name only with no other information. The DTD_IDENTIFIER value contains the type name and possibly other information such as the precision or length.

  • ROUTINE_TYPE

    PROCEDURE for stored procedures, FUNCTION for stored functions.

21.14 The INFORMATION_SCHEMA PARTITIONS Table

The PARTITIONS table provides information about table partitions. Each row in this table corresponds to an individual partition or subpartition of a partitioned table. For more information about partitioning tables, see Chapter 19, Partitioning.

The PARTITIONS table has these columns:

  • TABLE_CATALOG

    The name of the catalog to which the table belongs. This value is always def.

  • TABLE_SCHEMA

    The name of the database to which the table belongs.

  • TABLE_NAME

    The name of the table containing the partition.

  • PARTITION_NAME

    The name of the partition.

  • SUBPARTITION_NAME

    If the PARTITIONS table row represents a subpartition, the name of subpartition; otherwise NULL.

  • PARTITION_ORDINAL_POSITION

    All partitions are indexed in the same order as they are defined, with 1 being the number assigned to the first partition. The indexing can change as partitions are added, dropped, and reorganized; the number shown is this column reflects the current order, taking into account any indexing changes.

  • SUBPARTITION_ORDINAL_POSITION

    Subpartitions within a given partition are also indexed and reindexed in the same manner as partitions are indexed within a table.

  • PARTITION_METHOD

    One of the values RANGE, LIST, HASH, LINEAR HASH, KEY, or LINEAR KEY; that is, one of the available partitioning types as discussed in Section 19.2, “Partitioning Types”.

  • SUBPARTITION_METHOD

    One of the values HASH, LINEAR HASH, KEY, or LINEAR KEY; that is, one of the available subpartitioning types as discussed in Section 19.2.6, “Subpartitioning”.

  • PARTITION_EXPRESSION

    The expression for the partitioning function used in the CREATE TABLE or ALTER TABLE statement that created the table's current partitioning scheme.

    For example, consider a partitioned table created in the test database using this statement:

    CREATE TABLE tp (
        c1 INT,
        c2 INT,
        c3 VARCHAR(25)
    )
    PARTITION BY HASH(c1 + c2)
    PARTITIONS 4;
    

    The PARTITION_EXPRESSION column in a PARTITIONS table row for a partition from this table displays c1 + c2, as shown here:

    mysql> SELECT DISTINCT PARTITION_EXPRESSION
           FROM INFORMATION_SCHEMA.PARTITIONS
           WHERE TABLE_NAME='tp' AND TABLE_SCHEMA='test';
    +----------------------+
    | PARTITION_EXPRESSION |
    +----------------------+
    | c1 + c2              |
    +----------------------+
    
  • SUBPARTITION_EXPRESSION

    This works in the same fashion for the subpartitioning expression that defines the subpartitioning for a table as PARTITION_EXPRESSION does for the partitioning expression used to define a table's partitioning.

    If the table has no subpartitions, this column is NULL.

  • PARTITION_DESCRIPTION

    This column is used for RANGE and LIST partitions. For a RANGE partition, it contains the value set in the partition's VALUES LESS THAN clause, which can be either an integer or MAXVALUE. For a LIST partition, this column contains the values defined in the partition's VALUES IN clause, which is a list of comma-separated integer values.

    For partitions whose PARTITION_METHOD is other than RANGE or LIST, this column is always NULL.

  • TABLE_ROWS

    The number of table rows in the partition.

    For partitioned InnoDB tables, the row count given in the TABLE_ROWS column is only an estimated value used in SQL optimization, and may not always be exact.

    For NDB tables, you can also obtain this information using the ndb_desc utility.

  • AVG_ROW_LENGTH

    The average length of the rows stored in this partition or subpartition, in bytes. This is the same as DATA_LENGTH divided by TABLE_ROWS.

    For NDB tables, you can also obtain this information using the ndb_desc utility.

  • DATA_LENGTH

    The total length of all rows stored in this partition or subpartition, in bytes; that is, the total number of bytes stored in the partition or subpartition.

    For NDB tables, you can also obtain this information using the ndb_desc utility.

  • MAX_DATA_LENGTH

    The maximum number of bytes that can be stored in this partition or subpartition.

    For NDB tables, you can also obtain this information using the ndb_desc utility.

  • INDEX_LENGTH

    The length of the index file for this partition or subpartition, in bytes.

    For partitions of NDB tables, whether the tables use implicit or explicit partitioning, the INDEX_LENGTH column value is always 0. However, you can obtain equivalent information using the ndb_desc utility.

  • DATA_FREE

    The number of bytes allocated to the partition or subpartition but not used.

    For NDB tables, you can also obtain this information using the ndb_desc utility.

  • CREATE_TIME

    The time that the partition or subpartition was created.

    Prior to MySQL 5.6.25, for partitioned InnoDB tables, this column was always NULL. The correct creation time is shown in MySQL 5.6.25 and later. (Bug #17299181, Bug #69990)

  • UPDATE_TIME

    The time that the partition or subpartition was last modified.

    For partitioned InnoDB tables, the value is always NULL.

  • CHECK_TIME

    The last time that the table to which this partition or subpartition belongs was checked.

    For partitioned InnoDB tables, this column is always NULL.

  • CHECKSUM

    The checksum value, if any; otherwise NULL.

  • PARTITION_COMMENT

    The text of the comment, if the partition has one. If not, this value is empty.

    The maximum length for a partition comment is defined as 1024 characters, and the display width of the PARTITION_COMMENT column is also 1024, characters to match this limit.

  • NODEGROUP

    This is the nodegroup to which the partition belongs. This is relevant only to NDB Cluster tables; otherwise, the value is always 0.

  • TABLESPACE_NAME

    The name of the tablespace to which the partition belongs. The value is always DEFAULT, unless the table uses the NDB storage engine (see the Notes at the end of this section).

Notes

  • The PARTITIONS table is a nonstandard INFORMATION_SCHEMA table.

  • A table using any storage engine other than NDB and which is not partitioned has one row in the PARTITIONS table. However, the values of the PARTITION_NAME, SUBPARTITION_NAME, PARTITION_ORDINAL_POSITION, SUBPARTITION_ORDINAL_POSITION, PARTITION_METHOD, SUBPARTITION_METHOD, PARTITION_EXPRESSION, SUBPARTITION_EXPRESSION, and PARTITION_DESCRIPTION columns are all NULL. Also, the PARTITION_COMMENT column in this case is blank.

  • An NDB table which is not explicitly partitioned has one row in the PARTITIONS table for each data node in the NDB cluster. For each such row:

    • The SUBPARTITION_NAME, SUBPARTITION_ORDINAL_POSITION, SUBPARTITION_METHOD, PARTITION_EXPRESSION, SUBPARTITION_EXPRESSION, CREATE_TIME, UPDATE_TIME, CHECK_TIME, CHECKSUM, and TABLESPACE_NAME columns are all NULL.

    • The PARTITION_METHOD is always KEY.

    • The NODEGROUP column is default.

    • The PARTITION_EXPRESSION and PARTITION_COMMENT columns are empty.

21.15 The INFORMATION_SCHEMA PLUGINS Table

The PLUGINS table provides information about server plugins.

The PLUGINS table has these columns:

  • PLUGIN_NAME

    The name used to refer to the plugin in statements such as INSTALL PLUGIN and UNINSTALL PLUGIN.

  • PLUGIN_VERSION

    The version from the plugin's general type descriptor.

  • PLUGIN_STATUS

    The plugin status, one of ACTIVE, INACTIVE, DISABLED, or DELETED.

  • PLUGIN_TYPE

    The type of plugin, such as STORAGE ENGINE, INFORMATION_SCHEMA, or AUTHENTICATION.

  • PLUGIN_TYPE_VERSION

    The version from the plugin's type-specific descriptor.

  • PLUGIN_LIBRARY

    The name of the plugin shared library file. This is the name used to refer to the plugin file in statements such as INSTALL PLUGIN and UNINSTALL PLUGIN. This file is located in the directory named by the plugin_dir system variable. If the library name is NULL, the plugin is compiled in and cannot be uninstalled with UNINSTALL PLUGIN.

  • PLUGIN_LIBRARY_VERSION

    The plugin API interface version.

  • PLUGIN_AUTHOR

    The plugin author.

  • PLUGIN_DESCRIPTION

    A short description of the plugin.

  • PLUGIN_LICENSE

    How the plugin is licensed; for example, GPL.

  • LOAD_OPTION

    How the plugin was loaded. The value is OFF, ON, FORCE, or FORCE_PLUS_PERMANENT. See Section 5.5.1, “Installing and Uninstalling Plugins”.

Notes

  • The PLUGINS table is a nonstandard INFORMATION_SCHEMA table.

  • For plugins installed with INSTALL PLUGIN, the PLUGIN_NAME and PLUGIN_LIBRARY values are also registered in the mysql.plugin table.

  • For information about plugin data structures that form the basis of the information in the PLUGINS table, see Section 24.2, “The MySQL Plugin API”.

Plugin information is also available from the SHOW PLUGINS statement. See Section 13.7.5.26, “SHOW PLUGINS Syntax”. These statements are equivalent:

SELECT
  PLUGIN_NAME, PLUGIN_STATUS, PLUGIN_TYPE,
  PLUGIN_LIBRARY, PLUGIN_LICENSE
FROM INFORMATION_SCHEMA.PLUGINS;

SHOW PLUGINS;

21.16 The INFORMATION_SCHEMA PROCESSLIST Table

The PROCESSLIST table provides information about which threads are running.

The PROCESSLIST table has these columns:

  • ID

    The connection identifier. This is the same type of value displayed in the Id column of the SHOW PROCESSLIST statement, the PROCESSLIST_ID column of the Performance Schema threads table, and returned by the CONNECTION_ID() function.

  • USER

    The MySQL user who issued the statement. A value of system user refers to a nonclient thread spawned by the server to handle tasks internally. This could be the I/O or SQL thread used on replication slaves or a delayed-row handler. For system user, there is no host specified in the Host column. unauthenticated user refers to a thread that has become associated with a client connection but for which authentication of the client user has not yet been done. event_scheduler refers to the thread that monitors scheduled events (see Section 20.4, “Using the Event Scheduler”).

  • HOST

    The host name of the client issuing the statement (except for system user, for which there is no host). The host name for TCP/IP connections is reported in host_name:client_port format to make it easier to determine which client is doing what.

  • DB

    The default database, if one is selected; otherwise NULL.

  • COMMAND

    The type of command the thread is executing. For descriptions for thread commands, see Section 8.14, “Examining Thread Information”. The value of this column corresponds to the COM_xxx commands of the client/server protocol and Com_xxx status variables. See Section 5.1.9, “Server Status Variables”

  • TIME

    The time in seconds that the thread has been in its current state. For a slave SQL thread, the value is the number of seconds between the timestamp of the last replicated event and the real time of the slave machine. See Section 17.2.1, “Replication Implementation Details”.

  • STATE

    An action, event, or state that indicates what the thread is doing. Descriptions for STATE values can be found at Section 8.14, “Examining Thread Information”.

    Most states correspond to very quick operations. If a thread stays in a given state for many seconds, there might be a problem that needs to be investigated.

    For the SHOW PROCESSLIST statement, the value of STATE is NULL.

  • INFO

    The statement the thread is executing, or NULL if it is not executing any statement. The statement might be the one sent to the server, or an innermost statement if the statement executes other statements. For example, if a CALL statement executes a stored procedure that is executing a SELECT statement, the INFO value shows the SELECT statement.

Notes

  • The PROCESSLIST table is a nonstandard INFORMATION_SCHEMA table.

  • Like the output from the SHOW PROCESSLIST statement, the PROCESSLIST table shows information only about your own threads, unless you have the PROCESS privilege, in which case you will see information about other threads, too. As an anonymous user, you cannot see any rows at all.

  • If an SQL statement refers to the PROCESSLIST table, MySQL populates the entire table once, when statement execution begins, so there is read consistency during the statement. There is no read consistency for a multi-statement transaction.

Process information is also available from the mysqladmin processlist command, the SHOW PROCESSLIST statement, and the Performance Schema threads table (see Section 4.5.2, “mysqladmin — Client for Administering a MySQL Server”, Section 13.7.5.30, “SHOW PROCESSLIST Syntax”, and Section 22.12.10.3, “The threads Table”). In contrast to the INFORMATION_SCHEMA PROCESSLIST table and SHOW PROCESSLIST statement, which have negative performance consequences because they require a mutex, access to threads does not require a mutex and has minimal impact on server performance. The threads table also shows information about background threads, which the PROCESSLIST table and SHOW PROCESSLIST do not. This means that threads can be used to monitor activity the other thread information sources cannot.

The following statements are equivalent:

SELECT * FROM INFORMATION_SCHEMA.PROCESSLIST

SHOW FULL PROCESSLIST

21.17 The INFORMATION_SCHEMA PROFILING Table

The PROFILING table provides statement profiling information. Its contents correspond to the information produced by the SHOW PROFILE and SHOW PROFILES statements (see Section 13.7.5.31, “SHOW PROFILE Syntax”). The table is empty unless the profiling session variable is set to 1.

The PROFILING table has these columns:

  • QUERY_ID

    A numeric statement identifier.

  • SEQ

    A sequence number indicating the display order for rows with the same QUERY_ID value.

  • STATE

    The profiling state to which the row measurements apply.

  • DURATION

    How long statement execution remained in the given state, in seconds.

  • CPU_USER, CPU_SYSTEM

    User and system CPU use, in seconds.

  • CONTEXT_VOLUNTARY, CONTEXT_INVOLUNTARY

    How many voluntary and involuntary context switches occurred.

  • BLOCK_OPS_IN, BLOCK_OPS_OUT

    The number of block input and output operations.

  • MESSAGES_SENT, MESSAGES_RECEIVED

    The number of communication messages sent and received.

  • PAGE_FAULTS_MAJOR, PAGE_FAULTS_MINOR

    The number of major and minor page faults.

  • SWAPS

    How many swaps occurred.

  • SOURCE_FUNCTION, SOURCE_FILE, and SOURCE_LINE

    Information indicating where in the source code the profiled state executes.

Notes

  • The PROFILING table is a nonstandard INFORMATION_SCHEMA table.

Profiling information is also available from the SHOW PROFILE and SHOW PROFILES statements. See Section 13.7.5.31, “SHOW PROFILE Syntax”. For example, the following queries are equivalent:

SHOW PROFILE FOR QUERY 2;

SELECT STATE, FORMAT(DURATION, 6) AS DURATION
FROM INFORMATION_SCHEMA.PROFILING
WHERE QUERY_ID = 2 ORDER BY SEQ;

21.18 The INFORMATION_SCHEMA REFERENTIAL_CONSTRAINTS Table

The REFERENTIAL_CONSTRAINTS table provides information about foreign keys.

The REFERENTIAL_CONSTRAINTS table has these columns:

  • CONSTRAINT_CATALOG

    The name of the catalog to which the constraint belongs. This value is always def.

  • CONSTRAINT_SCHEMA

    The name of the schema (database) to which the constraint belongs.

  • CONSTRAINT_NAME

    The name of the constraint.

  • UNIQUE_CONSTRAINT_CATALOG

    The name of the catalog containing the unique constraint that the constraint references. This value is always def.

  • UNIQUE_CONSTRAINT_SCHEMA

    The name of the schema (database) containing the unique constraint that the constraint references.

  • UNIQUE_CONSTRAINT_NAME

    The name of the unique constraint that the constraint references.

  • MATCH_OPTION

    The value of the constraint MATCH attribute. The only valid value at this time is NONE.

  • UPDATE_RULE

    The value of the constraint ON UPDATE attribute. The possible values are CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION.

  • DELETE_RULE

    The value of the constraint ON DELETE attribute. The possible values are CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION.

  • TABLE_NAME

    The name of the table. This value is the same as in the TABLE_CONSTRAINTS table.

  • REFERENCED_TABLE_NAME

    The name of the table referenced by the constraint.

21.19 The INFORMATION_SCHEMA ROUTINES Table

The ROUTINES table provides information about stored routines (stored procedures and stored functions). The ROUTINES table does not include built-in SQL functions or user-defined functions (UDFs).

The column named mysql.proc Name indicates the mysql.proc table column that corresponds to the INFORMATION_SCHEMA ROUTINES table column, if any.

The ROUTINES table has these columns:

  • SPECIFIC_NAME

    The name of the routine.

  • ROUTINE_CATALOG

    The name of the catalog to which the routine belongs. This value is always def.

  • ROUTINE_SCHEMA

    The name of the schema (database) to which the routine belongs.

  • ROUTINE_NAME

    The name of the routine.

  • ROUTINE_TYPE

    PROCEDURE for stored procedures, FUNCTION for stored functions.

  • DATA_TYPE

    If the routine is a stored function, the return value data type. If the routine is a stored procedure, this value is empty.

    The DATA_TYPE value is the type name only with no other information. The DTD_IDENTIFIER value contains the type name and possibly other information such as the precision or length.

  • CHARACTER_MAXIMUM_LENGTH

    For stored function string return values, the maximum length in characters. If the routine is a stored procedure, this value is NULL.

  • CHARACTER_OCTET_LENGTH

    For stored function string return values, the maximum length in bytes. If the routine is a stored procedure, this value is NULL.

  • NUMERIC_PRECISION

    For stored function numeric return values, the numeric precision. If the routine is a stored procedure, this value is NULL.

  • NUMERIC_SCALE

    For stored function numeric return values, the numeric scale. If the routine is a stored procedure, this value is NULL.

  • DATETIME_PRECISION

    For stored function temporal return values, the fractional seconds precision. If the routine is a stored procedure, this value is NULL.

  • CHARACTER_SET_NAME

    For stored function character string return values, the character set name. If the routine is a stored procedure, this value is NULL.

  • COLLATION_NAME

    For stored function character string return values, the collation name. If the routine is a stored procedure, this value is NULL.

  • DTD_IDENTIFIER

    If the routine is a stored function, the return value data type. If the routine is a stored procedure, this value is empty.

    The DATA_TYPE value is the type name only with no other information. The DTD_IDENTIFIER value contains the type name and possibly other information such as the precision or length.

  • ROUTINE_BODY

    The language used for the routine definition. This value is always SQL.

  • ROUTINE_DEFINITION

    The text of the SQL statement executed by the routine.

  • EXTERNAL_NAME

    This value is always NULL.

  • EXTERNAL_LANGUAGE

    The language of the stored routine. MySQL calculates EXTERNAL_LANGUAGE thus:

    • If mysql.proc.language='SQL', EXTERNAL_LANGUAGE is NULL

    • Otherwise, EXTERNAL_LANGUAGE is what is in mysql.proc.language. However, we do not have external languages yet, so it is always NULL.

  • PARAMETER_STYLE

    This value is always SQL.

  • IS_DETERMINISTIC

    YES or NO, depending on whether the routine is defined with the DETERMINISTIC characteristic.

  • SQL_DATA_ACCESS

    The data access characteristic for the routine. The value is one of CONTAINS SQL, NO SQL, READS SQL DATA, or MODIFIES SQL DATA.

  • SQL_PATH

    This value is always NULL.

  • SECURITY_TYPE

    The routine SQL SECURITY characteristic. The value is one of DEFINER or INVOKER.

  • CREATED

    The date and time when the routine was created. This is a TIMESTAMP value.

  • LAST_ALTERED

    The date and time when the routine was last modified. This is a TIMESTAMP value. If the routine has not been modified since its creation, this value is the same as the CREATED value.

  • SQL_MODE

    The SQL mode in effect when the routine was created or altered, and under which the routine executes. For the permitted values, see Section 5.1.10, “Server SQL Modes”.

  • ROUTINE_COMMENT

    The text of the comment, if the routine has one. If not, this value is empty.

  • DEFINER

    The account of the user who created the routine, in 'user_name'@'host_name' format.

  • CHARACTER_SET_CLIENT

    The session value of the character_set_client system variable when the routine was created.

  • COLLATION_CONNECTION

    The session value of the collation_connection system variable when the routine was created.

  • DATABASE_COLLATION

    The collation of the database with which the routine is associated.

Notes

  • Information about stored function return values is also available in the PARAMETERS table. The return value row for a stored function can be identified as the row that has an ORDINAL_POSITION value of 0.

21.20 The INFORMATION_SCHEMA SCHEMATA Table

A schema is a database, so the SCHEMATA table provides information about databases.

The SCHEMATA table has these columns:

  • CATALOG_NAME

    The name of the catalog to which the schema belongs. This value is always def.

  • SCHEMA_NAME

    The name of the schema.

  • DEFAULT_CHARACTER_SET_NAME

    The schema default character set.

  • DEFAULT_COLLATION_NAME

    The schema default collation.

  • SQL_PATH

    This value is always NULL.

Schema names are also available from the SHOW DATABASES statement. See Section 13.7.5.15, “SHOW DATABASES Syntax”. The following statements are equivalent:

SELECT SCHEMA_NAME AS `Database`
  FROM INFORMATION_SCHEMA.SCHEMATA
  [WHERE SCHEMA_NAME LIKE 'wild']

SHOW DATABASES
  [LIKE 'wild']

21.21 The INFORMATION_SCHEMA SCHEMA_PRIVILEGES Table

The SCHEMA_PRIVILEGES table provides information about schema (database) privileges. It takes its values from the mysql.db system table.

The SCHEMA_PRIVILEGES table has these columns:

  • GRANTEE

    The name of the account to which the privilege is granted, in 'user_name'@'host_name' format.

  • TABLE_CATALOG

    The name of the catalog to which the schema belongs. This value is always def.

  • TABLE_SCHEMA

    The name of the schema.

  • PRIVILEGE_TYPE

    The privilege granted. The value can be any privilege that can be granted at the schema level; see Section 13.7.1.4, “GRANT Syntax”. Each row lists a single privilege, so there is one row per schema privilege held by the grantee.

  • IS_GRANTABLE

    YES if the user has the GRANT OPTION privilege, NO otherwise. The output does not list GRANT OPTION as a separate row with PRIVILEGE_TYPE='GRANT OPTION'.

Notes

The following statements are not equivalent:

SELECT ... FROM INFORMATION_SCHEMA.SCHEMA_PRIVILEGES

SHOW GRANTS ...

21.22 The INFORMATION_SCHEMA STATISTICS Table

The STATISTICS table provides information about table indexes.

The STATISTICS table has these columns:

  • TABLE_CATALOG

    The name of the catalog to which the table containing the index belongs. This value is always def.

  • TABLE_SCHEMA

    The name of the schema (database) to which the table containing the index belongs.

  • TABLE_NAME

    The name of the table containing the index.

  • NON_UNIQUE

    0 if the index cannot contain duplicates, 1 if it can.

  • INDEX_SCHEMA

    The name of the schema (database) to which the index belongs.

  • INDEX_NAME

    The name of the index. If the index is the primary key, the name is always PRIMARY.

  • SEQ_IN_INDEX

    The column sequence number in the index, starting with 1.

  • COLUMN_NAME

    The column name. See also the description for the EXPRESSION column.

  • COLLATION

    How the column is sorted in the index. This can have values A (ascending), D (descending), or NULL (not sorted).

  • CARDINALITY

    An estimate of the number of unique values in the index. To update this number, run ANALYZE TABLE or (for MyISAM tables) myisamchk -a.

    CARDINALITY is counted based on statistics stored as integers, so the value is not necessarily exact even for small tables. The higher the cardinality, the greater the chance that MySQL uses the index when doing joins.

  • SUB_PART

    The index prefix. That is, the number of indexed characters if the column is only partly indexed, NULL if the entire column is indexed.

    Note

    Prefix limits are measured in bytes. However, prefix lengths for index specifications in CREATE TABLE, ALTER TABLE, and CREATE INDEX statements are interpreted as number of characters for nonbinary string types (CHAR, VARCHAR, TEXT) and number of bytes for binary string types (BINARY, VARBINARY, BLOB). Take this into account when specifying a prefix length for a nonbinary string column that uses a multibyte character set.

    For additional information about index prefixes, see Section 8.3.4, “Column Indexes”, and Section 13.1.13, “CREATE INDEX Syntax”.

  • PACKED

    Indicates how the key is packed. NULL if it is not.

  • NULLABLE

    Contains YES if the column may contain NULL values and '' if not.

  • INDEX_TYPE

    The index method used (BTREE, FULLTEXT, HASH, RTREE).

  • COMMENT

    Information about the index not described in its own column, such as disabled if the index is disabled.

  • INDEX_COMMENT

    Any comment provided for the index with a COMMENT attribute when the index was created.

Notes

  • There is no standard INFORMATION_SCHEMA table for indexes. The MySQL column list is similar to what SQL Server 2000 returns for sp_statistics, except that QUALIFIER and OWNER are replaced with CATALOG and SCHEMA, respectively.

Information about table indexes is also available from the SHOW INDEX statement. See Section 13.7.5.23, “SHOW INDEX Syntax”. The following statements are equivalent:

SELECT * FROM INFORMATION_SCHEMA.STATISTICS
  WHERE table_name = 'tbl_name'
  AND table_schema = 'db_name'

SHOW INDEX
  FROM tbl_name
  FROM db_name

21.23 The INFORMATION_SCHEMA TABLES Table

The TABLES table provides information about tables in databases.

The TABLES table has these columns:

  • TABLE_CATALOG

    The name of the catalog to which the table belongs. This value is always def.

  • TABLE_SCHEMA

    The name of the schema (database) to which the table belongs.

  • TABLE_NAME

    The name of the table.

  • TABLE_TYPE

    BASE TABLE for a table, VIEW for a view, or SYSTEM VIEW for an INFORMATION_SCHEMA table.

    The TABLES table does not list TEMPORARY tables.

  • ENGINE

    The storage engine for the table. See Chapter 14, The InnoDB Storage Engine, and Chapter 15, Alternative Storage Engines.

    For partitioned tables, ENGINE shows the name of the storage engine used by all partitions.

  • VERSION

    The version number of the table's .frm file.

  • ROW_FORMAT

    The row-storage format (Fixed, Dynamic, Compressed, Redundant, Compact). For MyISAM tables, Dynamic corresponds to what myisamchk -dvv reports as Packed. InnoDB table format is either Redundant or Compact when using the Antelope file format, or Compressed or Dynamic when using the Barracuda file format.

  • TABLE_ROWS

    The number of rows. Some storage engines, such as MyISAM, store the exact count. For other storage engines, such as InnoDB, this value is an approximation, and may vary from the actual value by as much as 40% to 50%. In such cases, use SELECT COUNT(*) to obtain an accurate count.

    TABLE_ROWS is NULL for INFORMATION_SCHEMA tables.

    For InnoDB tables, the row count is only a rough estimate used in SQL optimization. (This is also true if the InnoDB table is partitioned.)

  • AVG_ROW_LENGTH

    The average row length.

    Refer to the notes at the end of this section for related information.

  • DATA_LENGTH

    For MyISAM, DATA_LENGTH is the length of the data file, in bytes.

    For InnoDB, DATA_LENGTH is the approximate amount of memory allocated for the clustered index, in bytes. Specifically, it is the clustered index size, in pages, multiplied by the InnoDB page size.

    Refer to the notes at the end of this section for information regarding other storage engines.

  • MAX_DATA_LENGTH

    For MyISAM, MAX_DATA_LENGTH is maximum length of the data file. This is the total number of bytes of data that can be stored in the table, given the data pointer size used.

    Unused for InnoDB.

    Refer to the notes at the end of this section for information regarding other storage engines.

  • INDEX_LENGTH

    For MyISAM, INDEX_LENGTH is the length of the index file, in bytes.

    For InnoDB, INDEX_LENGTH is the approximate amount of memory allocated for non-clustered indexes, in bytes. Specifically, it is the sum of non-clustered index sizes, in pages, multiplied by the InnoDB page size.

    Refer to the notes at the end of this section for information regarding other storage engines.

  • DATA_FREE

    The number of allocated but unused bytes.

    InnoDB tables report the free space of the tablespace to which the table belongs. For a table located in the shared tablespace, this is the free space of the shared tablespace. If you are using multiple tablespaces and the table has its own tablespace, the free space is for only that table. Free space means the number of bytes in completely free extents minus a safety margin. Even if free space displays as 0, it may be possible to insert rows as long as new extents need not be allocated.

    For NDB Cluster, DATA_FREE shows the space allocated on disk for, but not used by, a Disk Data table or fragment on disk. (In-memory data resource usage is reported by the DATA_LENGTH column.)

    For partitioned tables, this value is only an estimate and may not be absolutely correct. A more accurate method of obtaining this information in such cases is to query the INFORMATION_SCHEMA PARTITIONS table, as shown in this example:

    SELECT SUM(DATA_FREE)
        FROM  INFORMATION_SCHEMA.PARTITIONS
        WHERE TABLE_SCHEMA = 'mydb'
        AND   TABLE_NAME   = 'mytable';
    

    For more information, see Section 21.14, “The INFORMATION_SCHEMA PARTITIONS Table”.

  • AUTO_INCREMENT

    The next AUTO_INCREMENT value.

  • CREATE_TIME

    When the table was created.

    Prior to MySQL 5.6.25, for partitioned InnoDB tables, the CREATE_TIME column shows NULL. This column shows the correct table creation time for such tables in MySQL 5.6.25 and later. (Bug #17299181, Bug #69990)

  • UPDATE_TIME

    When the data file was last updated. For some storage engines, this value is NULL. For example, InnoDB stores multiple tables in its system tablespace and the data file timestamp does not apply. Even with file-per-table mode with each InnoDB table in a separate .ibd file, change buffering can delay the write to the data file, so the file modification time is different from the time of the last insert, update, or delete. For MyISAM, the data file timestamp is used; however, on Windows the timestamp is not updated by updates, so the value is inaccurate.

    For partitioned InnoDB tables, UPDATE_TIME is always NULL.

  • CHECK_TIME

    When the table was last checked. Not all storage engines update this time, in which case, the value is always NULL.

    For partitioned InnoDB tables, CHECK_TIME is always NULL.

  • TABLE_COLLATION

    The table default collation. The output does not explicitly list the table default character set, but the collation name begins with the character set name.

  • CHECKSUM

    The live checksum value, if any.

  • CREATE_OPTIONS

    Extra options used with CREATE TABLE. The original options from when CREATE TABLE was executed are retained and the options reported here may differ from the active table settings and options.

    CREATE_OPTIONS shows partitioned if the table is partitioned.

  • TABLE_COMMENT

    The comment used when creating the table (or information as to why MySQL could not access the table information).

Notes

  • For NDB tables, the output of this statement shows appropriate values for the AVG_ROW_LENGTH and DATA_LENGTH columns, with the exception that BLOB columns are not taken into account.

  • For NDB tables, DATA_LENGTH includes data stored in main memory only; the MAX_DATA_LENGTH and DATA_FREE columns apply to Disk Data.

  • For NDB Cluster Disk Data tables, MAX_DATA_LENGTH shows the space allocated for the disk part of a Disk Data table or fragment. (In-memory data resource usage is reported by the DATA_LENGTH column.)

  • For MEMORY tables, the DATA_LENGTH, MAX_DATA_LENGTH, and INDEX_LENGTH values approximate the actual amount of allocated memory. The allocation algorithm reserves memory in large amounts to reduce the number of allocation operations.

  • For views, all TABLES columns are NULL except that TABLE_NAME indicates the view name and TABLE_COMMENT says VIEW.

Table information is also available from the SHOW TABLE STATUS and SHOW TABLES statements. See Section 13.7.5.37, “SHOW TABLE STATUS Syntax”, and Section 13.7.5.38, “SHOW TABLES Syntax”. The following statements are equivalent:

SELECT
    TABLE_NAME, ENGINE, VERSION, ROW_FORMAT, TABLE_ROWS, AVG_ROW_LENGTH,
    DATA_LENGTH, MAX_DATA_LENGTH, INDEX_LENGTH, DATA_FREE, AUTO_INCREMENT,
    CREATE_TIME, UPDATE_TIME, CHECK_TIME, TABLE_COLLATION, CHECKSUM,
    CREATE_OPTIONS, TABLE_COMMENT
  FROM INFORMATION_SCHEMA.TABLES
  WHERE table_schema = 'db_name'
  [AND table_name LIKE 'wild']

SHOW TABLE STATUS
  FROM db_name
  [LIKE 'wild']

The following statements are equivalent:

SELECT
  TABLE_NAME, TABLE_TYPE
  FROM INFORMATION_SCHEMA.TABLES
  WHERE table_schema = 'db_name'
  [AND table_name LIKE 'wild']

SHOW FULL TABLES
  FROM db_name
  [LIKE 'wild']

21.24 The INFORMATION_SCHEMA TABLESPACES Table

The TABLESPACES table provides information about active MySQL Cluster tablespaces.

The TABLESPACES table has these columns:

  • TABLESPACE_NAME

    The name of the tablespace.

  • ENGINE

    The name of the storage engine that uses the tablespace.

  • TABLESPACE_TYPE

    The tablespace type.

  • LOGFILE_GROUP_NAME

    The name of the logfile group assigned to the tablespace.

  • EXTENT_SIZE

    The size in bytes of the extents used by files that belong to the tablespace.

  • AUTOEXTEND_SIZE

    Unused.

  • MAXIMUM_SIZE

    Unused.

  • NODEGROUP_ID

    Unused.

  • TABLESPACE_COMMENT

    Unused.

Notes

21.25 The INFORMATION_SCHEMA TABLE_CONSTRAINTS Table

The TABLE_CONSTRAINTS table describes which tables have constraints.

The TABLE_CONSTRAINTS table has these columns:

  • CONSTRAINT_CATALOG

    The name of the catalog to which the constraint belongs. This value is always def.

  • CONSTRAINT_SCHEMA

    The name of the schema (database) to which the constraint belongs.

  • TABLE_SCHEMA

    The name of the schema (database) to which the table belongs.

  • TABLE_NAME

    The name of the table.

  • The CONSTRAINT_TYPE

    The type of constraint. The value can be UNIQUE, PRIMARY KEY, FOREIGN KEY, or CHECK. This is a CHAR (not ENUM) column. The CHECK value is not available until MySQL supports CHECK.

    The UNIQUE and PRIMARY KEY information is about the same as what you get from the Key_name column in the output from SHOW INDEX when the Non_unique column is 0.

21.26 The INFORMATION_SCHEMA TABLE_PRIVILEGES Table

The TABLE_PRIVILEGES table provides information about table privileges. It takes its values from the mysql.tables_priv system table.

The TABLE_PRIVILEGES table has these columns:

  • GRANTEE

    The name of the account to which the privilege is granted, in 'user_name'@'host_name' format.

  • TABLE_CATALOG

    The name of the catalog to which the table belongs. This value is always def.

  • TABLE_SCHEMA

    The name of the schema (database) to which the table belongs.

  • TABLE_NAME

    The name of the table.

  • PRIVILEGE_TYPE

    The privilege granted. The value can be any privilege that can be granted at the table level; see Section 13.7.1.4, “GRANT Syntax”. Each row lists a single privilege, so there is one row per table privilege held by the grantee.

  • IS_GRANTABLE

    YES if the user has the GRANT OPTION privilege, NO otherwise. The output does not list GRANT OPTION as a separate row with PRIVILEGE_TYPE='GRANT OPTION'.

Notes

The following statements are not equivalent:

SELECT ... FROM INFORMATION_SCHEMA.TABLE_PRIVILEGES

SHOW GRANTS ...

21.27 The INFORMATION_SCHEMA TRIGGERS Table

The TRIGGERS table provides information about triggers. To see information about a table's triggers, you must have the TRIGGER privilege for the table.

The TRIGGERS table has these columns:

  • TRIGGER_CATALOG

    The name of the catalog to which the trigger belongs. This value is always def.

  • TRIGGER_SCHEMA

    The name of the schema (database) to which the trigger belongs.

  • TRIGGER_NAME

    The name of the trigger.

  • EVENT_MANIPULATION

    The trigger event. This is the type of operation on the associated table for which the trigger activates. The value is INSERT (a row was inserted), DELETE (a row was deleted), or UPDATE (a row was modified).

  • EVENT_OBJECT_CATALOG, EVENT_OBJECT_SCHEMA, and EVENT_OBJECT_TABLE

    As noted in Section 20.3, “Using Triggers”, every trigger is associated with exactly one table. These columns indicate the catalog and schema (database) in which this table occurs, and the table name, respectively. The EVENT_OBJECT_CATALOG value is always def.

  • ACTION_ORDER

    The ordinal position of the trigger's action within the list of all similar triggers on the same table. This value is always 0 because it is not possible to have more than one trigger with the same EVENT_MANIPULATION and ACTION_TIMING on the same table.

  • ACTION_CONDITION

    This value is always NULL.

  • ACTION_STATEMENT

    The trigger body; that is, the statement executed when the trigger activates. This text uses UTF-8 encoding.

  • ACTION_ORIENTATION

    This value is always ROW.

  • ACTION_TIMING

    Whether the trigger activates before or after the triggering event. The value is BEFORE or AFTER.

  • ACTION_REFERENCE_OLD_TABLE

    This value is always NULL.

  • ACTION_REFERENCE_NEW_TABLE

    This value is always NULL.

  • ACTION_REFERENCE_OLD_ROW and ACTION_REFERENCE_NEW_ROW

    The old and new column identifiers, respectively. The ACTION_REFERENCE_OLD_ROW value is always OLD and the ACTION_REFERENCE_NEW_ROW value is always NEW.

  • CREATED

    This value is always NULL.

  • SQL_MODE

    The SQL mode in effect when the trigger was created, and under which the trigger executes. For the permitted values, see Section 5.1.10, “Server SQL Modes”.

  • DEFINER

    The account of the user who created the trigger, in 'user_name'@'host_name' format.

  • CHARACTER_SET_CLIENT

    The session value of the character_set_client system variable when the trigger was created.

  • COLLATION_CONNECTION

    The session value of the collation_connection system variable when the trigger was created.

  • DATABASE_COLLATION

    The collation of the database with which the trigger is associated.

Example

The following example uses the ins_sum trigger defined in Section 20.3, “Using Triggers”:

mysql> SELECT * FROM INFORMATION_SCHEMA.TRIGGERS
       WHERE TRIGGER_SCHEMA='test' AND TRIGGER_NAME='ins_sum'\G
*************************** 1. row ***************************
           TRIGGER_CATALOG: def
            TRIGGER_SCHEMA: test
              TRIGGER_NAME: ins_sum
        EVENT_MANIPULATION: INSERT
      EVENT_OBJECT_CATALOG: def
       EVENT_OBJECT_SCHEMA: test
        EVENT_OBJECT_TABLE: account
              ACTION_ORDER: 0
          ACTION_CONDITION: NULL
          ACTION_STATEMENT: SET @sum = @sum + NEW.amount
        ACTION_ORIENTATION: ROW
             ACTION_TIMING: BEFORE
ACTION_REFERENCE_OLD_TABLE: NULL
ACTION_REFERENCE_NEW_TABLE: NULL
  ACTION_REFERENCE_OLD_ROW: OLD
  ACTION_REFERENCE_NEW_ROW: NEW
                   CREATED: NULL
                  SQL_MODE: NO_ENGINE_SUBSTITUTION
                   DEFINER: me@localhost
      CHARACTER_SET_CLIENT: utf8
      COLLATION_CONNECTION: utf8_general_ci
        DATABASE_COLLATION: latin1_swedish_ci

Trigger information is also available from the SHOW TRIGGERS statement. See Section 13.7.5.39, “SHOW TRIGGERS Syntax”.

21.28 The INFORMATION_SCHEMA USER_PRIVILEGES Table

The USER_PRIVILEGES table provides information about global privileges. It takes its values from the mysql.user system table.

The USER_PRIVILEGES table has these columns:

  • GRANTEE

    The name of the account to which the privilege is granted, in 'user_name'@'host_name' format.

  • TABLE_CATALOG

    The name of the catalog. This value is always def.

  • PRIVILEGE_TYPE

    The privilege granted. The value can be any privilege that can be granted at the global level; see Section 13.7.1.4, “GRANT Syntax”. Each row lists a single privilege, so there is one row per global privilege held by the grantee.

  • IS_GRANTABLE

    YES if the user has the GRANT OPTION privilege, NO otherwise. The output does not list GRANT OPTION as a separate row with PRIVILEGE_TYPE='GRANT OPTION'.

Notes

The following statements are not equivalent:

SELECT ... FROM INFORMATION_SCHEMA.USER_PRIVILEGES

SHOW GRANTS ...

21.29 The INFORMATION_SCHEMA VIEWS Table

The VIEWS table provides information about views in databases. You must have the SHOW VIEW privilege to access this table.

The VIEWS table has these columns:

  • TABLE_CATALOG

    The name of the catalog to which the view belongs. This value is always def.

  • TABLE_SCHEMA

    The name of the schema (database) to which the view belongs.

  • TABLE_NAME

    The name of the view.

  • VIEW_DEFINITION

    The SELECT statement that provides the definition of the view. This column has most of what you see in the Create Table column that SHOW CREATE VIEW produces. Skip the words before SELECT and skip the words WITH CHECK OPTION. Suppose that the original statement was:

    CREATE VIEW v AS
      SELECT s2,s1 FROM t
      WHERE s1 > 5
      ORDER BY s1
      WITH CHECK OPTION;
    

    Then the view definition looks like this:

    SELECT s2,s1 FROM t WHERE s1 > 5 ORDER BY s1
    
  • CHECK_OPTION

    The value of the CHECK_OPTION attribute. The value is one of NONE, CASCADE, or LOCAL.

  • IS_UPDATABLE

    MySQL sets a flag, called the view updatability flag, at CREATE VIEW time. The flag is set to YES (true) if UPDATE and DELETE (and similar operations) are legal for the view. Otherwise, the flag is set to NO (false). The IS_UPDATABLE column in the VIEWS table displays the status of this flag. It means that the server always knows whether a view is updatable.

    If a view is not updatable, statements such UPDATE, DELETE, and INSERT are illegal and are rejected. (Even if a view is updatable, it might not be possible to insert into it; for details, refer to Section 20.5.3, “Updatable and Insertable Views”.)

  • DEFINER

    The account of the user who created the view, in 'user_name'@'host_name' format.

  • SECURITY_TYPE

    The view SQL SECURITY characteristic. The value is one of DEFINER or INVOKER.

  • CHARACTER_SET_CLIENT

    The session value of the character_set_client system variable when the view was created.

  • COLLATION_CONNECTION

    The session value of the collation_connection system variable when the view was created.

Notes

MySQL permits different sql_mode settings to tell the server the type of SQL syntax to support. For example, you might use the ANSI SQL mode to ensure MySQL correctly interprets the standard SQL concatenation operator, the double bar (||), in your queries. If you then create a view that concatenates items, you might worry that changing the sql_mode setting to a value different from ANSI could cause the view to become invalid. But this is not the case. No matter how you write out a view definition, MySQL always stores it the same way, in a canonical form. Here is an example that shows how the server changes a double bar concatenation operator to a CONCAT() function:

mysql> SET sql_mode = 'ANSI';
Query OK, 0 rows affected (0.00 sec)

mysql> CREATE VIEW test.v AS SELECT 'a' || 'b' as col1;
Query OK, 0 rows affected (0.00 sec)

mysql> SELECT VIEW_DEFINITION FROM INFORMATION_SCHEMA.VIEWS
       WHERE TABLE_SCHEMA = 'test' AND TABLE_NAME = 'v';
+----------------------------------+
| VIEW_DEFINITION                  |
+----------------------------------+
| select concat('a','b') AS `col1` |
+----------------------------------+
1 row in set (0.00 sec)

The advantage of storing a view definition in canonical form is that changes made later to the value of sql_mode do not affect the results from the view. However, an additional consequence is that comments prior to SELECT are stripped from the definition by the server.

21.30 INFORMATION_SCHEMA InnoDB Tables

This section provides table definitions for InnoDB INFORMATION_SCHEMA tables. For related information and examples, see Section 14.15, “InnoDB INFORMATION_SCHEMA Tables”.

InnoDB INFORMATION_SCHEMA tables can be used to monitor ongoing InnoDB activity, to detect inefficiencies before they turn into issues, or to troubleshoot performance and capacity issues. As your database becomes bigger and busier, running up against the limits of your hardware capacity, you monitor and tune these aspects to keep the database running smoothly.

21.30.1 The INFORMATION_SCHEMA INNODB_BUFFER_PAGE Table

The INNODB_BUFFER_PAGE table provides information about each page in the InnoDB buffer pool.

For related usage information and examples, see Section 14.15.5, “InnoDB INFORMATION_SCHEMA Buffer Pool Tables”.

Warning

Querying the INNODB_BUFFER_PAGE table can affect performance. Do not query this table on a production system unless you are aware of the performance impact and have determined it to be acceptable. To avoid impacting performance on a production system, reproduce the issue you want to investigate and query buffer pool statistics on a test instance.

The INNODB_BUFFER_PAGE table has these columns:

  • POOL_ID

    The buffer pool ID. This is an identifier to distinguish between multiple buffer pool instances.

  • BLOCK_ID

    The buffer pool block ID.

  • SPACE

    The tablespace ID; the same value as INNODB_SYS_TABLES.SPACE.

  • PAGE_NUMBER

    The page number.

  • PAGE_TYPE

    The page type. The following table shows the permitted values.

    Table 21.1 INNODB_BUFFER_PAGE.PAGE_TYPE Values

    Page Type Description
    ALLOCATED Freshly allocated page
    BLOB Uncompressed BLOB page
    COMPRESSED_BLOB2 Subsequent comp BLOB page
    COMPRESSED_BLOB First compressed BLOB page
    EXTENT_DESCRIPTOR Extent descriptor page
    FILE_SPACE_HEADER File space header
    IBUF_BITMAP Insert buffer bitmap
    IBUF_FREE_LIST Insert buffer free list
    IBUF_INDEX Insert buffer index
    INDEX B-tree node
    INODE Index node
    SYSTEM System page
    TRX_SYSTEM Transaction system data
    UNDO_LOG Undo log page
    UNKNOWN Unknown

  • FLUSH_TYPE

    The flush type.

  • FIX_COUNT

    The number of threads using this block within the buffer pool. When zero, the block is eligible to be evicted.

  • IS_HASHED

    Whether a hash index has been built on this page.

  • NEWEST_MODIFICATION

    The Log Sequence Number of the youngest modification.

  • OLDEST_MODIFICATION

    The Log Sequence Number of the oldest modification.

  • ACCESS_TIME

    An abstract number used to judge the first access time of the page.

  • TABLE_NAME

    The name of the table the page belongs to. This column is applicable only to pages with a PAGE_TYPE value of INDEX.

  • INDEX_NAME

    The name of the index the page belongs to. This can be the name of a clustered index or a secondary index. This column is applicable only to pages with a PAGE_TYPE value of INDEX.

  • NUMBER_RECORDS

    The number of records within the page.

  • DATA_SIZE

    The sum of the sizes of the records. This column is applicable only to pages with a PAGE_TYPE value of INDEX.

  • COMPRESSED_SIZE

    The compressed page size. NULL for pages that are not compressed.

  • PAGE_STATE

    The page state. The following table shows the permitted values.

    Table 21.2 INNODB_BUFFER_PAGE.PAGE_STATE Values

    Page State Description
    FILE_PAGE A buffered file page
    MEMORY Contains a main memory object
    NOT_USED In the free list
    NULL Clean compressed pages, compressed pages in the flush list, pages used as buffer pool watch sentinels
    READY_FOR_USE A free page
    REMOVE_HASH Hash index should be removed before placing in the free list

  • IO_FIX

    Whether any I/O is pending for this page: IO_NONE = no pending I/O, IO_READ = read pending, IO_WRITE = write pending.

  • IS_OLD

    Whether the block is in the sublist of old blocks in the LRU list.

  • FREE_PAGE_CLOCK

    The value of the freed_page_clock counter when the block was the last placed at the head of the LRU list. The freed_page_clock counter tracks the number of blocks removed from the end of the LRU list.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE LIMIT 1\G
*************************** 1. row ***************************
            POOL_ID: 0
           BLOCK_ID: 0
              SPACE: 97
        PAGE_NUMBER: 2473
          PAGE_TYPE: INDEX
         FLUSH_TYPE: 1
          FIX_COUNT: 0
          IS_HASHED: YES
NEWEST_MODIFICATION: 733855581
OLDEST_MODIFICATION: 0
        ACCESS_TIME: 3378385672
         TABLE_NAME: `employees`.`salaries`
         INDEX_NAME: PRIMARY
     NUMBER_RECORDS: 468
          DATA_SIZE: 14976
    COMPRESSED_SIZE: 0
         PAGE_STATE: FILE_PAGE
             IO_FIX: IO_NONE
             IS_OLD: YES
    FREE_PAGE_CLOCK: 66

Notes

  • This table is useful primarily for expert-level performance monitoring, or when developing performance-related extensions for MySQL.

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

  • When tables, table rows, partitions, or indexes are deleted, associated pages remain in the buffer pool until space is required for other data. The INNODB_BUFFER_PAGE table reports information about these pages until they are evicted from the buffer pool. For more information about how the InnoDB manages buffer pool data, see Section 14.5.1, “Buffer Pool”.

21.30.2 The INFORMATION_SCHEMA INNODB_BUFFER_PAGE_LRU Table

The INNODB_BUFFER_PAGE_LRU table provides information about the pages in the InnoDB buffer pool; in particular, how they are ordered in the LRU list that determines which pages to evict from the buffer pool when it becomes full.

The INNODB_BUFFER_PAGE_LRU table has the same columns as the INNODB_BUFFER_PAGE table, except that the INNODB_BUFFER_PAGE_LRU table has LRU_POSITION and COMPRESSED columns instead of BLOCK_ID and PAGE_STATE columns.

For related usage information and examples, see Section 14.15.5, “InnoDB INFORMATION_SCHEMA Buffer Pool Tables”.

Warning

Querying the INNODB_BUFFER_PAGE_LRU table can affect performance. Do not query this table on a production system unless you are aware of the performance impact and have determined it to be acceptable. To avoid impacting performance on a production system, reproduce the issue you want to investigate and query buffer pool statistics on a test instance.

The INNODB_BUFFER_PAGE_LRU table has these columns:

  • POOL_ID

    The buffer pool ID. This is an identifier to distinguish between multiple buffer pool instances.

  • LRU_POSITION

    The position of the page in the LRU list.

  • SPACE

    The tablespace ID; the same value as INNODB_SYS_TABLES.SPACE.

  • PAGE_NUMBER

    The page number.

  • PAGE_TYPE

    The page type. The following table shows the permitted values.

    Table 21.3 INNODB_BUFFER_PAGE_LRU.PAGE_TYPE Values

    Page Type Description
    ALLOCATED Freshly allocated page
    BLOB Uncompressed BLOB page
    COMPRESSED_BLOB2 Subsequent comp BLOB page
    COMPRESSED_BLOB First compressed BLOB page
    EXTENT_DESCRIPTOR Extent descriptor page
    FILE_SPACE_HEADER File space header
    IBUF_BITMAP Insert buffer bitmap
    IBUF_FREE_LIST Insert buffer free list
    IBUF_INDEX Insert buffer index
    INDEX B-tree node
    INODE Index node
    SYSTEM System page
    TRX_SYSTEM Transaction system data
    UNDO_LOG Undo log page
    UNKNOWN Unknown

  • FLUSH_TYPE

    The flush type.

  • FIX_COUNT

    The number of threads using this block within the buffer pool. When zero, the block is eligible to be evicted.

  • IS_HASHED

    Whether a hash index has been built on this page.

  • NEWEST_MODIFICATION

    The Log Sequence Number of the youngest modification.

  • OLDEST_MODIFICATION

    The Log Sequence Number of the oldest modification.

  • ACCESS_TIME

    An abstract number used to judge the first access time of the page.

  • TABLE_NAME

    The name of the table the page belongs to. This column is applicable only to pages with a PAGE_TYPE value of INDEX.

  • INDEX_NAME

    The name of the index the page belongs to. This can be the name of a clustered index or a secondary index. This column is applicable only to pages with a PAGE_TYPE value of INDEX.

  • NUMBER_RECORDS

    The number of records within the page.

  • DATA_SIZE

    The sum of the sizes of the records. This column is applicable only to pages with a PAGE_TYPE value of INDEX.

  • COMPRESSED_SIZE

    The compressed page size. NULL for pages that are not compressed.

  • COMPRESSED

    Whether the page is compressed.

  • IO_FIX

    Whether any I/O is pending for this page: IO_NONE = no pending I/O, IO_READ = read pending, IO_WRITE = write pending.

  • IS_OLD

    Whether the block is in the sublist of old blocks in the LRU list.

  • FREE_PAGE_CLOCK

    The value of the freed_page_clock counter when the block was the last placed at the head of the LRU list. The freed_page_clock counter tracks the number of blocks removed from the end of the LRU list.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_BUFFER_PAGE_LRU LIMIT 1\G
*************************** 1. row ***************************
            POOL_ID: 0
       LRU_POSITION: 0
              SPACE: 97
        PAGE_NUMBER: 1984
          PAGE_TYPE: INDEX
         FLUSH_TYPE: 1
          FIX_COUNT: 0
          IS_HASHED: YES
NEWEST_MODIFICATION: 719490396
OLDEST_MODIFICATION: 0
        ACCESS_TIME: 3378383796
         TABLE_NAME: `employees`.`salaries`
         INDEX_NAME: PRIMARY
     NUMBER_RECORDS: 468
          DATA_SIZE: 14976
    COMPRESSED_SIZE: 0
         COMPRESSED: NO
             IO_FIX: IO_NONE
             IS_OLD: YES
    FREE_PAGE_CLOCK: 0

Notes

  • This table is useful primarily for expert-level performance monitoring, or when developing performance-related extensions for MySQL.

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

  • Querying this table can require MySQL to allocate a large block of contiguous memory, more than 64 bytes times the number of active pages in the buffer pool. This allocation could potentially cause an out-of-memory error, especially for systems with multi-gigabyte buffer pools.

  • Querying this table requires MySQL to lock the data structure representing the buffer pool while traversing the LRU list, which can reduce concurrency, especially for systems with multi-gigabyte buffer pools.

  • When tables, table rows, partitions, or indexes are deleted, associated pages remain in the buffer pool until space is required for other data. The INNODB_BUFFER_PAGE_LRU table reports information about these pages until they are evicted from the buffer pool. For more information about how the InnoDB manages buffer pool data, see Section 14.5.1, “Buffer Pool”.

21.30.3 The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table

The INNODB_BUFFER_POOL_STATS table provides much of the same buffer pool information provided in SHOW ENGINE INNODB STATUS output. Much of the same information may also be obtained using InnoDB buffer pool server status variables.

The idea of making pages in the buffer pool young or not young refers to transferring them between the sublists at the head and tail of the buffer pool data structure. Pages made young take longer to age out of the buffer pool, while pages made not young are moved much closer to the point of eviction.

For related usage information and examples, see Section 14.15.5, “InnoDB INFORMATION_SCHEMA Buffer Pool Tables”.

The INNODB_BUFFER_POOL_STATS table has these columns:

  • POOL_ID

    The buffer pool ID. This is an identifier to distinguish between multiple buffer pool instances.

  • POOL_SIZE

    The InnoDB buffer pool size in pages.

  • FREE_BUFFERS

    The number of free pages in the InnoDB buffer pool.

  • DATABASE_PAGES

    The number of pages in the InnoDB buffer pool containing data. This number includes both dirty and clean pages.

  • OLD_DATABASE_PAGES

    The number of pages in the old buffer pool sublist.

  • MODIFIED_DATABASE_PAGES

    The number of modified (dirty) database pages.

  • PENDING_DECOMPRESS

    The number of pages pending decompression.

  • PENDING_READS

    The number of pending reads.

  • PENDING_FLUSH_LRU

    The number of pages pending flush in the LRU.

  • PENDING_FLUSH_LIST

    The number of pages pending flush in the flush list.

  • PAGES_MADE_YOUNG

    The number of pages made young.

  • PAGES_NOT_MADE_YOUNG

    The number of pages not made young.

  • PAGES_MADE_YOUNG_RATE

    The number of pages made young per second (pages made young since the last printout / time elapsed).

  • PAGES_MADE_NOT_YOUNG_RATE

    The number of pages not made per second (pages not made young since the last printout / time elapsed).

  • NUMBER_PAGES_READ

    The number of pages read.

  • NUMBER_PAGES_CREATED

    The number of pages created.

  • NUMBER_PAGES_WRITTEN

    The number of pages written.

  • PAGES_READ_RATE

    The number of pages read per second (pages read since the last printout / time elapsed).

  • PAGES_CREATE_RATE

    The number of pages created per second (pages created since the last printout / time elapsed).

  • PAGES_WRITTEN_RATE

    The number of pages written per second (pages written since the last printout / time elapsed).

  • NUMBER_PAGES_GET

    The number of logical read requests.

  • HIT_RATE

    The buffer pool hit rate.

  • YOUNG_MAKE_PER_THOUSAND_GETS

    The number of pages made young per thousand gets.

  • NOT_YOUNG_MAKE_PER_THOUSAND_GETS

    The number of pages not made young per thousand gets.

  • NUMBER_PAGES_READ_AHEAD

    The number of pages read ahead.

  • NUMBER_READ_AHEAD_EVICTED

    The number of pages read into the InnoDB buffer pool by the read-ahead background thread that were subsequently evicted without having been accessed by queries.

  • READ_AHEAD_RATE

    The read-ahead rate per second (pages read ahead since the last printout / time elapsed).

  • READ_AHEAD_EVICTED_RATE

    The number of read-ahead pages evicted without access per second (read-ahead pages not accessed since the last printout / time elapsed).

  • LRU_IO_TOTAL

    Total LRU I/O.

  • LRU_IO_CURRENT

    LRU I/O for the current interval.

  • UNCOMPRESS_TOTAL

    The total number of pages decompressed.

  • UNCOMPRESS_CURRENT

    The number of pages decompressed in the current interval.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_BUFFER_POOL_STATS\G
*************************** 1. row ***************************
                         POOL_ID: 0
                       POOL_SIZE: 8192
                    FREE_BUFFERS: 1
                  DATABASE_PAGES: 8085
              OLD_DATABASE_PAGES: 2964
         MODIFIED_DATABASE_PAGES: 0
              PENDING_DECOMPRESS: 0
                   PENDING_READS: 0
               PENDING_FLUSH_LRU: 0
              PENDING_FLUSH_LIST: 0
                PAGES_MADE_YOUNG: 22821
            PAGES_NOT_MADE_YOUNG: 3544303
           PAGES_MADE_YOUNG_RATE: 357.62602199870594
       PAGES_MADE_NOT_YOUNG_RATE: 0
               NUMBER_PAGES_READ: 2389
            NUMBER_PAGES_CREATED: 12385
            NUMBER_PAGES_WRITTEN: 13111
                 PAGES_READ_RATE: 0
               PAGES_CREATE_RATE: 0
              PAGES_WRITTEN_RATE: 0
                NUMBER_PAGES_GET: 33322210
                        HIT_RATE: 1000
    YOUNG_MAKE_PER_THOUSAND_GETS: 18
NOT_YOUNG_MAKE_PER_THOUSAND_GETS: 0
         NUMBER_PAGES_READ_AHEAD: 2024
       NUMBER_READ_AHEAD_EVICTED: 0
                 READ_AHEAD_RATE: 0
         READ_AHEAD_EVICTED_RATE: 0
                    LRU_IO_TOTAL: 0
                  LRU_IO_CURRENT: 0
                UNCOMPRESS_TOTAL: 0
              UNCOMPRESS_CURRENT: 0

Notes

  • This table is useful primarily for expert-level performance monitoring, or when developing performance-related extensions for MySQL.

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

21.30.4 The INFORMATION_SCHEMA INNODB_CMP and INNODB_CMP_RESET Tables

The INNODB_CMP and INNODB_CMP_RESET tables provide status information on operations related to compressed InnoDB tables.

The INNODB_CMP and INNODB_CMP_RESET tables have these columns:

  • PAGE_SIZE

    The compressed page size in bytes.

  • COMPRESS_OPS

    The number of times a B-tree page of size PAGE_SIZE has been compressed. Pages are compressed whenever an empty page is created or the space for the uncompressed modification log runs out.

  • COMPRESS_OPS_OK

    The number of times a B-tree page of size PAGE_SIZE has been successfully compressed. This count should never exceed COMPRESS_OPS.

  • COMPRESS_TIME

    The total time in seconds used for attempts to compress B-tree pages of size PAGE_SIZE.

  • UNCOMPRESS_OPS

    The number of times a B-tree page of size PAGE_SIZE has been uncompressed. B-tree pages are uncompressed whenever compression fails or at first access when the uncompressed page does not exist in the buffer pool.

  • UNCOMPRESS_TIME

    The total time in seconds used for uncompressing B-tree pages of the size PAGE_SIZE.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_CMP\G
*************************** 1. row ***************************
      page_size: 1024
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 0
uncompress_time: 0
*************************** 2. row ***************************
      page_size: 2048
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 0
uncompress_time: 0
*************************** 3. row ***************************
      page_size: 4096
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 0
uncompress_time: 0
*************************** 4. row ***************************
      page_size: 8192
   compress_ops: 86955
compress_ops_ok: 81182
  compress_time: 27
 uncompress_ops: 26828
uncompress_time: 5
*************************** 5. row ***************************
      page_size: 16384
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 0
uncompress_time: 0

Notes

21.30.5 The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables

The INNODB_CMPMEM and INNODB_CMPMEM_RESET tables provide status information on compressed pages within the InnoDB buffer pool.

The INNODB_CMPMEM and INNODB_CMPMEM_RESET tables have these columns:

  • PAGE_SIZE

    The block size in bytes. Each record of this table describes blocks of this size.

  • BUFFER_POOL_INSTANCE

    A unique identifier for the buffer pool instance.

  • PAGES_USED

    The number of blocks of size PAGE_SIZE that are currently in use.

  • PAGES_FREE

    The number of blocks of size PAGE_SIZE that are currently available for allocation. This column shows the external fragmentation in the memory pool. Ideally, these numbers should be at most 1.

  • RELOCATION_OPS

    The number of times a block of size PAGE_SIZE has been relocated. The buddy system can relocate the allocated buddy neighbor of a freed block when it tries to form a bigger freed block. Reading from the INNODB_CMPMEM_RESET table resets this count.

  • RELOCATION_TIME

    The total time in microseconds used for relocating blocks of size PAGE_SIZE. Reading from the table INNODB_CMPMEM_RESET resets this count.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_CMPMEM\G
*************************** 1. row ***************************
           page_size: 1024
buffer_pool_instance: 0
          pages_used: 0
          pages_free: 0
      relocation_ops: 0
     relocation_time: 0
*************************** 2. row ***************************
           page_size: 2048
buffer_pool_instance: 0
          pages_used: 0
          pages_free: 0
      relocation_ops: 0
     relocation_time: 0
*************************** 3. row ***************************
           page_size: 4096
buffer_pool_instance: 0
          pages_used: 0
          pages_free: 0
      relocation_ops: 0
     relocation_time: 0
*************************** 4. row ***************************
           page_size: 8192
buffer_pool_instance: 0
          pages_used: 7673
          pages_free: 15
      relocation_ops: 4638
     relocation_time: 0
*************************** 5. row ***************************
           page_size: 16384
buffer_pool_instance: 0
          pages_used: 0
          pages_free: 0
      relocation_ops: 0
     relocation_time: 0

Notes

21.30.6 The INFORMATION_SCHEMA INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET Tables

The INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET tables provide status information on operations related to compressed InnoDB tables and indexes, with separate statistics for each combination of database, table, and index, to help you evaluate the performance and usefulness of compression for specific tables.

For a compressed InnoDB table, both the table data and all the secondary indexes are compressed. In this context, the table data is treated as just another index, one that happens to contain all the columns: the clustered index.

The INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET tables have these columns:

  • DATABASE_NAME

    The schema (database) containing the applicable table.

  • TABLE_NAME

    The table to monitor for compression statistics.

  • INDEX_NAME

    The index to monitor for compression statistics.

  • COMPRESS_OPS

    The number of compression operations attempted. Pages are compressed whenever an empty page is created or the space for the uncompressed modification log runs out.

  • COMPRESS_OPS_OK

    The number of successful compression operations. Subtract from the COMPRESS_OPS value to get the number of compression failures. Divide by the COMPRESS_OPS value to get the percentage of compression failures.

  • COMPRESS_TIME

    The total time in seconds used for compressing data in this index.

  • UNCOMPRESS_OPS

    The number of uncompression operations performed. Compressed InnoDB pages are uncompressed whenever compression fails, or the first time a compressed page is accessed in the buffer pool and the uncompressed page does not exist.

  • UNCOMPRESS_TIME

    The total time in seconds used for uncompressing data in this index.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_CMP_PER_INDEX\G
*************************** 1. row ***************************
  database_name: employees
     table_name: salaries
     index_name: PRIMARY
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 23451
uncompress_time: 4
*************************** 2. row ***************************
  database_name: employees
     table_name: salaries
     index_name: emp_no
   compress_ops: 0
compress_ops_ok: 0
  compress_time: 0
 uncompress_ops: 1597
uncompress_time: 0

Notes

21.30.7 The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table

The INNODB_FT_BEING_DELETED table provides a snapshot of the INNODB_FT_DELETED table; it is used only during an OPTIMIZE TABLE maintenance operation. When OPTIMIZE TABLE is run, the INNODB_FT_BEING_DELETED table is emptied, and DOC_ID values are removed from the INNODB_FT_DELETED table. Because the contents of INNODB_FT_BEING_DELETED typically have a short lifetime, this table has limited utility for monitoring or debugging. For information about running OPTIMIZE TABLE on tables with FULLTEXT indexes, see Section 12.9.6, “Fine-Tuning MySQL Full-Text Search”.

This table is empty initially. Before querying it, set the value of the innodb_ft_aux_table system variable to the name (including the database name) of the table that contains the FULLTEXT index; for example test/articles. The output appears similar to the example provided for the INNODB_FT_DELETED table.

For related usage information and examples, see Section 14.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables”.

The INNODB_FT_BEING_DELETED table has these columns:

  • DOC_ID

    The document ID of the row that is in the process of being deleted. This value might reflect the value of an ID column that you defined for the underlying table, or it can be a sequence value generated by InnoDB when the table contains no suitable column. This value is used when you do text searches, to skip rows in the INNODB_FT_INDEX_TABLE table before data for deleted rows is physically removed from the FULLTEXT index by an OPTIMIZE TABLE statement. For more information, see Optimizing InnoDB Full-Text Indexes.

Notes

21.30.8 The INFORMATION_SCHEMA INNODB_FT_CONFIG Table

The INNODB_FT_CONFIG table provides metadata about the FULLTEXT index and associated processing for an InnoDB table.

This table is empty initially. Before querying it, set the value of the innodb_ft_aux_table system variable to the name (including the database name) of the table that contains the FULLTEXT index; for example test/articles.

For related usage information and examples, see Section 14.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables”.

The INNODB_FT_CONFIG table has these columns:

  • KEY

    The name designating an item of metadata for an InnoDB table containing a FULLTEXT index.

    The values for this column might change, depending on the needs for performance tuning and debugging for InnoDB full-text processing. The key names and their meanings include:

    • optimize_checkpoint_limit: The number of seconds after which an OPTIMIZE TABLE run stops.

    • synced_doc_id: The next DOC_ID to be issued.

    • stopword_table_name: The database/table name for a user-defined stopword table. The VALUE column is empty if there is no user-defined stopword table.

    • use_stopword: Indicates whether a stopword table is used, which is defined when the FULLTEXT index is created.

  • VALUE

    The value associated with the corresponding KEY column, reflecting some limit or current value for an aspect of a FULLTEXT index for an InnoDB table.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_FT_CONFIG;
+---------------------------+-------------------+
| KEY                       | VALUE             |
+---------------------------+-------------------+
| optimize_checkpoint_limit | 180               |
| synced_doc_id             | 0                 |
| stopword_table_name       | test/my_stopwords |
| use_stopword              | 1                 |
+---------------------------+-------------------+

Notes

21.30.9 The INFORMATION_SCHEMA INNODB_FT_DEFAULT_STOPWORD Table

The INNODB_FT_DEFAULT_STOPWORD table holds a list of stopwords that are used by default when creating a FULLTEXT index on InnoDB tables. For information about the default InnoDB stopword list and how to define your own stopword lists, see Section 12.9.4, “Full-Text Stopwords”.

For related usage information and examples, see Section 14.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables”.

The INNODB_FT_DEFAULT_STOPWORD table has these columns:

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_FT_DEFAULT_STOPWORD;
+-------+
| value |
+-------+
| a     |
| about |
| an    |
| are   |
| as    |
| at    |
| be    |
| by    |
| com   |
| de    |
| en    |
| for   |
| from  |
| how   |
| i     |
| in    |
| is    |
| it    |
| la    |
| of    |
| on    |
| or    |
| that  |
| the   |
| this  |
| to    |
| was   |
| what  |
| when  |
| where |
| who   |
| will  |
| with  |
| und   |
| the   |
| www   |
+-------+
36 rows in set (0.00 sec)

Notes

21.30.10 The INFORMATION_SCHEMA INNODB_FT_DELETED Table

The INNODB_FT_DELETED table stores rows that are deleted from the FULLTEXT index for an InnoDB table. To avoid expensive index reorganization during DML operations for an InnoDB FULLTEXT index, the information about newly deleted words is stored separately, filtered out of search results when you do a text search, and removed from the main search index only when you issue an OPTIMIZE TABLE statement for the InnoDB table. For more information, see Optimizing InnoDB Full-Text Indexes.

This table is empty initially. Before querying it, set the value of the innodb_ft_aux_table system variable to the name (including the database name) of the table that contains the FULLTEXT index; for example test/articles.

For related usage information and examples, see Section 14.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables”.

The INNODB_FT_DELETED table has these columns:

  • DOC_ID

    The document ID of the newly deleted row. This value might reflect the value of an ID column that you defined for the underlying table, or it can be a sequence value generated by InnoDB when the table contains no suitable column. This value is used when you do text searches, to skip rows in the INNODB_FT_INDEX_TABLE table before data for deleted rows is physically removed from the FULLTEXT index by an OPTIMIZE TABLE statement. For more information, see Optimizing InnoDB Full-Text Indexes.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_FT_DELETED;
+--------+
| DOC_ID |
+--------+
|      6 |
|      7 |
|      8 |
+--------+

Notes

21.30.11 The INFORMATION_SCHEMA INNODB_FT_INDEX_CACHE Table

The INNODB_FT_INDEX_CACHE table provides token information about newly inserted rows in a FULLTEXT index. To avoid expensive index reorganization during DML operations, the information about newly indexed words is stored separately, and combined with the main search index only when OPTIMIZE TABLE is run, when the server is shut down, or when the cache size exceeds a limit defined by the innodb_ft_cache_size or innodb_ft_total_cache_size system variable.

This table is empty initially. Before querying it, set the value of the innodb_ft_aux_table system variable to the name (including the database name) of the table that contains the FULLTEXT index; for example test/articles.

For related usage information and examples, see Section 14.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables”.

The INNODB_FT_INDEX_CACHE table has these columns:

  • WORD

    A word extracted from the text of a newly inserted row.

  • FIRST_DOC_ID

    The first document ID in which this word appears in the FULLTEXT index.

  • LAST_DOC_ID

    The last document ID in which this word appears in the FULLTEXT index.

  • DOC_COUNT

    The number of rows in which this word appears in the FULLTEXT index. The same word can occur several times within the cache table, once for each combination of DOC_ID and POSITION values.

  • DOC_ID

    The document ID of the newly inserted row. This value might reflect the value of an ID column that you defined for the underlying table, or it can be a sequence value generated by InnoDB when the table contains no suitable column.

  • POSITION

    The position of this particular instance of the word within the relevant document identified by the DOC_ID value. The value does not represent an absolute position; it is an offset added to the POSITION of the previous instance of that word.

Notes

  • This table is empty initially. Before querying it, set the value of the innodb_ft_aux_table system variable to the name (including the database name) of the table that contains the FULLTEXT index; for example test/articles. The following example demonstrates how to use the innodb_ft_aux_table system variable to show information about a FULLTEXT index for a specified table.

    mysql> USE test;
    
    mysql> CREATE TABLE articles (
             id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
             title VARCHAR(200),
             body TEXT,
             FULLTEXT (title,body)
           ) ENGINE=InnoDB;
    
    mysql> INSERT INTO articles (title,body) VALUES
           ('MySQL Tutorial','DBMS stands for DataBase ...'),
           ('How To Use MySQL Well','After you went through a ...'),
           ('Optimizing MySQL','In this tutorial we will show ...'),
           ('1001 MySQL Tricks','1. Never run mysqld as root. 2. ...'),
           ('MySQL vs. YourSQL','In the following database comparison ...'),
           ('MySQL Security','When configured properly, MySQL ...');
    
    mysql> SET GLOBAL innodb_ft_aux_table = 'test/articles';
    
    mysql> SELECT WORD, DOC_COUNT, DOC_ID, POSITION
           FROM INFORMATION_SCHEMA.INNODB_FT_INDEX_CACHE LIMIT 5;
    +------------+-----------+--------+----------+
    | WORD       | DOC_COUNT | DOC_ID | POSITION |
    +------------+-----------+--------+----------+
    | 1001       |         1 |      4 |        0 |
    | after      |         1 |      2 |       22 |
    | comparison |         1 |      5 |       44 |
    | configured |         1 |      6 |       20 |
    | database   |         2 |      1 |       31 |
    +------------+-----------+--------+----------+
    
  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

  • For more information about InnoDB FULLTEXT search, see Section 14.6.2.3, “InnoDB FULLTEXT Indexes”, and Section 12.9, “Full-Text Search Functions”.

21.30.12 The INFORMATION_SCHEMA INNODB_FT_INDEX_TABLE Table

The INNODB_FT_INDEX_TABLE table provides information about the inverted index used to process text searches against the FULLTEXT index of an InnoDB table.

This table is empty initially. Before querying it, set the value of the innodb_ft_aux_table system variable to the name (including the database name) of the table that contains the FULLTEXT index; for example test/articles.

For related usage information and examples, see Section 14.15.4, “InnoDB INFORMATION_SCHEMA FULLTEXT Index Tables”.

The INNODB_FT_INDEX_TABLE table has these columns:

  • WORD

    A word extracted from the text of the columns that are part of a FULLTEXT.

  • FIRST_DOC_ID

    The first document ID in which this word appears in the FULLTEXT index.

  • LAST_DOC_ID

    The last document ID in which this word appears in the FULLTEXT index.

  • DOC_COUNT

    The number of rows in which this word appears in the FULLTEXT index. The same word can occur several times within the cache table, once for each combination of DOC_ID and POSITION values.

  • DOC_ID

    The document ID of the row containing the word. This value might reflect the value of an ID column that you defined for the underlying table, or it can be a sequence value generated by InnoDB when the table contains no suitable column.

  • POSITION

    The position of this particular instance of the word within the relevant document identified by the DOC_ID value.

Notes

  • This table is empty initially. Before querying it, set the value of the innodb_ft_aux_table system variable to the name (including the database name) of the table that contains the FULLTEXT index; for example test/articles. The following example demonstrates how to use the innodb_ft_aux_table system variable to show information about a FULLTEXT index for a specified table. Before information for newly inserted rows appears in INNODB_FT_INDEX_TABLE, the FULLTEXT index cache must be flushed to disk. This is accomplished by running an OPTIMIZE TABLE operation on the indexed table with the innodb_optimize_fulltext_only system variable enabled. (The example disables that variable again at the end because it is intended to be enabled only temporarily.)

    mysql> USE test;
    
    mysql> CREATE TABLE articles (
             id INT UNSIGNED AUTO_INCREMENT NOT NULL PRIMARY KEY,
             title VARCHAR(200),
             body TEXT,
             FULLTEXT (title,body)
           ) ENGINE=InnoDB;
    
    mysql> INSERT INTO articles (title,body) VALUES
           ('MySQL Tutorial','DBMS stands for DataBase ...'),
           ('How To Use MySQL Well','After you went through a ...'),
           ('Optimizing MySQL','In this tutorial we will show ...'),
           ('1001 MySQL Tricks','1. Never run mysqld as root. 2. ...'),
           ('MySQL vs. YourSQL','In the following database comparison ...'),
           ('MySQL Security','When configured properly, MySQL ...');
    
    mysql> SET GLOBAL innodb_optimize_fulltext_only=ON;
    
    mysql> OPTIMIZE TABLE articles;
    +---------------+----------+----------+----------+
    | Table         | Op       | Msg_type | Msg_text |
    +---------------+----------+----------+----------+
    | test.articles | optimize | status   | OK       |
    +---------------+----------+----------+----------+
    
    mysql> SET GLOBAL innodb_ft_aux_table = 'test/articles';
    
    mysql> SELECT WORD, DOC_COUNT, DOC_ID, POSITION
           FROM INFORMATION_SCHEMA.INNODB_FT_INDEX_TABLE LIMIT 5;
    +------------+-----------+--------+----------+
    | WORD       | DOC_COUNT | DOC_ID | POSITION |
    +------------+-----------+--------+----------+
    | 1001       |         1 |      4 |        0 |
    | after      |         1 |      2 |       22 |
    | comparison |         1 |      5 |       44 |
    | configured |         1 |      6 |       20 |
    | database   |         2 |      1 |       31 |
    +------------+-----------+--------+----------+
    
    mysql> SET GLOBAL innodb_optimize_fulltext_only=OFF;
    
  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

  • For more information about InnoDB FULLTEXT search, see Section 14.6.2.3, “InnoDB FULLTEXT Indexes”, and Section 12.9, “Full-Text Search Functions”.

21.30.13 The INFORMATION_SCHEMA INNODB_LOCKS Table

The INNODB_LOCKS table provides information about each lock that an InnoDB transaction has requested but not yet acquired, and each lock that a transaction holds that is blocking another transaction.

The INNODB_LOCKS table has these columns:

  • LOCK_ID

    A unique lock ID number, internal to InnoDB. Treat it as an opaque string. Although LOCK_ID currently contains TRX_ID, the format of the data in LOCK_ID is subject to change at any time. Do not write applications that parse the LOCK_ID value.

  • LOCK_TRX_ID

    The ID of the transaction holding the lock. To obtain details about the transaction, join this column with the TRX_ID column of the INNODB_TRX table.

  • LOCK_MODE

    How the lock is requested. Permitted lock mode descriptors are S, X, IS, IX, GAP, AUTO_INC, and UNKNOWN. Lock mode descriptors may be used in combination to identify particular lock modes. For information about InnoDB lock modes, see Section 14.7.1, “InnoDB Locking”.

  • LOCK_TYPE

    The type of lock. Permitted values are RECORD for a row-level lock, TABLE for a table-level lock.

  • LOCK_TABLE

    The name of the table that has been locked or contains locked records.

  • LOCK_INDEX

    The name of the index, if LOCK_TYPE is RECORD; otherwise NULL.

  • LOCK_SPACE

    The tablespace ID of the locked record, if LOCK_TYPE is RECORD; otherwise NULL.

  • LOCK_PAGE

    The page number of the locked record, if LOCK_TYPE is RECORD; otherwise NULL.

  • LOCK_REC

    The heap number of the locked record within the page, if LOCK_TYPE is RECORD; otherwise NULL.

  • LOCK_DATA

    The data associated with the lock, if any. Values are primary key values of the locked record if LOCK_TYPE is RECORD, otherwise NULL. This column contains the values of the primary key columns in the locked row, formatted as a valid SQL string (ready to be copied to SQL statements). If there is no primary key, LOCK_DATA is the unique InnoDB internal row ID number. If a gap lock is taken for key values or ranges above the largest value in the index, LOCK_DATA reports supremum pseudo-record. When the page containing the locked record is not in the buffer pool (in the case that it was paged out to disk while the lock was held), InnoDB does not fetch the page from disk, to avoid unnecessary disk operations. Instead, LOCK_DATA is set to NULL.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCKS\G
*************************** 1. row ***************************
    lock_id: 3723:72:3:2
lock_trx_id: 3723
  lock_mode: X
  lock_type: RECORD
 lock_table: `mysql`.`t`
 lock_index: PRIMARY
 lock_space: 72
  lock_page: 3
   lock_rec: 2
  lock_data: 1, 9
*************************** 2. row ***************************
    lock_id: 3722:72:3:2
lock_trx_id: 3722
  lock_mode: S
  lock_type: RECORD
 lock_table: `mysql`.`t`
 lock_index: PRIMARY
 lock_space: 72
  lock_page: 3
   lock_rec: 2
  lock_data: 1, 9

Notes

21.30.14 The INFORMATION_SCHEMA INNODB_LOCK_WAITS Table

The INNODB_LOCK_WAITS table contains one or more rows for each blocked InnoDB transaction, indicating the lock it has requested and any locks that are blocking that request.

The INNODB_LOCK_WAITS table has these columns:

  • REQUESTING_TRX_ID

    The ID of the requesting (blocked) transaction.

  • REQUESTED_LOCK_ID

    The ID of the lock for which a transaction is waiting. To obtain details about the lock, join this column with the LOCK_ID column of the INNODB_LOCKS table.

  • BLOCKING_TRX_ID

    The ID of the blocking transaction.

  • BLOCKING_LOCK_ID

    The ID of a lock held by a transaction blocking another transaction from proceeding. To obtain details about the lock, join this column with the LOCK_ID column of the INNODB_LOCKS table.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_LOCK_WAITS\G
*************************** 1. row ***************************
requesting_trx_id: 3396
requested_lock_id: 3396:91:3:2
  blocking_trx_id: 3395
 blocking_lock_id: 3395:91:3:2

Notes

21.30.15 The INFORMATION_SCHEMA INNODB_METRICS Table

The INNODB_METRICS table provides a wide variety of InnoDB performance information, complementing the specific focus areas of the Performance Schema tables for InnoDB. With simple queries, you can check the overall health of the system. With more detailed queries, you can diagnose issues such as performance bottlenecks, resource shortages, and application issues.

Each monitor represents a point within the InnoDB source code that is instrumented to gather counter information. Each counter can be started, stopped, and reset. You can also perform these actions for a group of counters using their common module name.

By default, relatively little data is collected. To start, stop, and reset counters, set one of the system variables innodb_monitor_enable, innodb_monitor_disable, innodb_monitor_reset, or innodb_monitor_reset_all, using the name of the counter, the name of the module, a wildcard match for such a name using the % character, or the special keyword all.

For usage information, see Section 14.15.6, “InnoDB INFORMATION_SCHEMA Metrics Table”.

The INNODB_METRICS table has these columns:

  • NAME

    A unique name for the counter.

  • SUBSYSTEM

    The aspect of InnoDB that the metric applies to.

  • COUNT

    The value since the counter was enabled.

  • MAX_COUNT

    The maximum value since the counter was enabled.

  • MIN_COUNT

    The minimum value since the counter was enabled.

  • AVG_COUNT

    The average value since the counter was enabled.

  • COUNT_RESET

    The counter value since it was last reset. (The _RESET columns act like the lap counter on a stopwatch: you can measure the activity during some time interval, while the cumulative figures are still available in COUNT, MAX_COUNT, and so on.)

  • MAX_COUNT_RESET

    The maximum counter value since it was last reset.

  • MIN_COUNT_RESET

    The minimum counter value since it was last reset.

  • AVG_COUNT_RESET

    The average counter value since it was last reset.

  • TIME_ENABLED

    The timestamp of the last start.

  • TIME_DISABLED

    The timestamp of the last stop.

  • TIME_ELAPSED

    The elapsed time in seconds since the counter started.

  • TIME_RESET

    The timestamp of the last reset.

  • STATUS

    Whether the counter is still running (enabled) or stopped (disabled).

  • TYPE

    Whether the item is a cumulative counter, or measures the current value of some resource.

  • COMMENT

    The counter description.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_METRICS WHERE NAME='dml_inserts'\G
*************************** 1. row ***************************
           NAME: dml_inserts
      SUBSYSTEM: dml
          COUNT: 3
      MAX_COUNT: 3
      MIN_COUNT: NULL
      AVG_COUNT: 0.046153846153846156
    COUNT_RESET: 3
MAX_COUNT_RESET: 3
MIN_COUNT_RESET: NULL
AVG_COUNT_RESET: NULL
   TIME_ENABLED: 2014-12-04 14:18:28
  TIME_DISABLED: NULL
   TIME_ELAPSED: 65
     TIME_RESET: NULL
         STATUS: enabled
           TYPE: status_counter
        COMMENT: Number of rows inserted

Notes

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

21.30.16 The INFORMATION_SCHEMA INNODB_SYS_COLUMNS Table

The INNODB_SYS_COLUMNS table provides metadata about InnoDB table columns, equivalent to the information from the SYS_COLUMNS table in the InnoDB data dictionary.

For related usage information and examples, see Section 14.15.3, “InnoDB INFORMATION_SCHEMA System Tables”.

The INNODB_SYS_COLUMNS table has these columns:

  • TABLE_ID

    An identifier representing the table associated with the column; the same value as INNODB_SYS_TABLES.TABLE_ID.

  • NAME

    The name of the column. These names can be uppercase or lowercase depending on the lower_case_table_names setting. There are no special system-reserved names for columns.

  • POS

    The ordinal position of the column within the table, starting from 0 and incrementing sequentially. When a column is dropped, the remaining columns are reordered so that the sequence has no gaps.

  • MTYPE

    Stands for main type. A numeric identifier for the column type. 1 = VARCHAR, 2 = CHAR, 3 = FIXBINARY, 4 = BINARY, 5 = BLOB, 6 = INT, 7 = SYS_CHILD, 8 = SYS, 9 = FLOAT, 10 = DOUBLE, 11 = DECIMAL, 12 = VARMYSQL, 13 = MYSQL.

  • PRTYPE

    The InnoDB precise type, a binary value with bits representing MySQL data type, character set code, and nullability.

  • LEN

    The column length, for example 4 for INT and 8 for BIGINT. For character columns in multibyte character sets, this length value is the maximum length in bytes needed to represent a definition such as VARCHAR(N); that is, it might be 2*N, 3*N, and so on depending on the character encoding.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_COLUMNS where TABLE_ID = 71\G
*************************** 1. row ***************************
TABLE_ID: 71
    NAME: col1
     POS: 0
   MTYPE: 6
  PRTYPE: 1027
     LEN: 4
*************************** 2. row ***************************
TABLE_ID: 71
    NAME: col2
     POS: 1
   MTYPE: 2
  PRTYPE: 524542
     LEN: 10
*************************** 3. row ***************************
TABLE_ID: 71
    NAME: col3
     POS: 2
   MTYPE: 1
  PRTYPE: 524303
     LEN: 10

Notes

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

21.30.17 The INFORMATION_SCHEMA INNODB_SYS_DATAFILES Table

The INNODB_SYS_DATAFILES table provides data file path information for InnoDB tablespaces, equivalent to the information in the SYS_DATAFILES table in the InnoDB data dictionary.

For related usage information and examples, see Section 14.15.3, “InnoDB INFORMATION_SCHEMA System Tables”.

The INNODB_SYS_DATAFILES table has these columns:

  • SPACE

    The tablespace ID.

  • PATH

    The tablespace data file path. If a file-per-table tablespace is created in a location outside the MySQL data directory, the path value is a fully qualified directory path. Otherwise, the path is relative to the data directory.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_DATAFILES WHERE SPACE = 57\G
*************************** 1. row ***************************
SPACE: 57
 PATH: ./test/t1.ibd

Notes

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

21.30.18 The INFORMATION_SCHEMA INNODB_SYS_FIELDS Table

The INNODB_SYS_FIELDS table provides metadata about the key columns (fields) of InnoDB indexes, equivalent to the information from the SYS_FIELDS table in the InnoDB data dictionary.

For related usage information and examples, see Section 14.15.3, “InnoDB INFORMATION_SCHEMA System Tables”.

The INNODB_SYS_FIELDS table has these columns:

  • INDEX_ID

    An identifier for the index associated with this key field; the same value as INNODB_SYS_INDEXES.INDEX_ID.

  • NAME

    The name of the original column from the table; the same value as INNODB_SYS_COLUMNS.NAME.

  • POS

    The ordinal position of the key field within the index, starting from 0 and incrementing sequentially. When a column is dropped, the remaining columns are reordered so that the sequence has no gaps.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_FIELDS WHERE INDEX_ID = 117\G
*************************** 1. row ***************************
INDEX_ID: 117
    NAME: col1
     POS: 0

Notes

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

21.30.19 The INFORMATION_SCHEMA INNODB_SYS_FOREIGN Table

The INNODB_SYS_FOREIGN table provides metadata about InnoDB foreign keys, equivalent to the information from the SYS_FOREIGN table in the InnoDB data dictionary.

For related usage information and examples, see Section 14.15.3, “InnoDB INFORMATION_SCHEMA System Tables”.

The INNODB_SYS_FOREIGN table has these columns:

  • ID

    The name (not a numeric value) of the foreign key index, preceded by the schema (database) name; for example, test/products_fk.

  • FOR_NAME

    The name of the child table in this foreign key relationship.

  • REF_NAME

    The name of the parent table in this foreign key relationship.

  • N_COLS

    The number of columns in the foreign key index.

  • TYPE

    A collection of bit flags with information about the foreign key column, ORed together. 0 = ON DELETE/UPDATE RESTRICT, 1 = ON DELETE CASCADE, 2 = ON DELETE SET NULL, 4 = ON UPDATE CASCADE, 8 = ON UPDATE SET NULL, 16 = ON DELETE NO ACTION, 32 = ON UPDATE NO ACTION.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_FOREIGN\G
*************************** 1. row ***************************
      ID: test/fk1
FOR_NAME: test/child
REF_NAME: test/parent
  N_COLS: 1
    TYPE: 1

Notes

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

21.30.20 The INFORMATION_SCHEMA INNODB_SYS_FOREIGN_COLS Table

The INNODB_SYS_FOREIGN_COLS table provides status information about the columns of InnoDB foreign keys, equivalent to the information from the SYS_FOREIGN_COLS table in the InnoDB data dictionary.

For related usage information and examples, see Section 14.15.3, “InnoDB INFORMATION_SCHEMA System Tables”.

The INNODB_SYS_FOREIGN_COLS table has these columns:

  • ID

    The foreign key index associated with this index key field, using the same value as INNODB_SYS_FOREIGN.ID.

  • FOR_COL_NAME

    The name of the associated column in the child table.

  • REF_COL_NAME

    The name of the associated column in the parent table.

  • POS

    The ordinal position of this key field within the foreign key index, starting from 0.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_FOREIGN_COLS WHERE ID = 'test/fk1'\G
*************************** 1. row ***************************
          ID: test/fk1
FOR_COL_NAME: parent_id
REF_COL_NAME: id
         POS: 0

Notes

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

21.30.21 The INFORMATION_SCHEMA INNODB_SYS_INDEXES Table

The INNODB_SYS_INDEXES table provides metadata about InnoDB indexes, equivalent to the information in the internal SYS_INDEXES table in the InnoDB data dictionary.

For related usage information and examples, see Section 14.15.3, “InnoDB INFORMATION_SCHEMA System Tables”.

The INNODB_SYS_INDEXES table has these columns:

  • INDEX_ID

    An identifier for the index. Index identifiers are unique across all the databases in an instance.

  • NAME

    The name of the index. Most indexes created implicitly by InnoDB have consistent names but the index names are not necessarily unique. Examples: PRIMARY for a primary key index, GEN_CLUST_INDEX for the index representing a primary key when one is not specified, and ID_IND, FOR_IND, and REF_IND for foreign key constraints.

  • TABLE_ID

    An identifier representing the table associated with the index; the same value as INNODB_SYS_TABLES.TABLE_ID.

  • TYPE

    A numeric value derived from bit-level information that identifies the index type. 0 = nonunique secondary index; 1 = automatically generated clustered index (GEN_CLUST_INDEX); 2 = unique nonclustered index; 3 = clustered index; 32 = full-text index

  • N_FIELDS

    The number of columns in the index key. For GEN_CLUST_INDEX indexes, this value is 0 because the index is created using an artificial value rather than a real table column.

  • PAGE_NO

    The root page number of the index B-tree. For full-text indexes, the PAGE_NO column is unused and set to -1 (FIL_NULL) because the full-text index is laid out in several B-trees (auxiliary tables).

  • SPACE

    An identifier for the tablespace where the index resides. 0 means the InnoDB system tablespace. Any other number represents a table created with a separate .ibd file in file-per-table mode. This identifier stays the same after a TRUNCATE TABLE statement. Because all indexes for a table reside in the same tablespace as the table, this value is not necessarily unique.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_INDEXES WHERE TABLE_ID = 74\G
*************************** 1. row ***************************
INDEX_ID: 116
    NAME: GEN_CLUST_INDEX
TABLE_ID: 74
    TYPE: 1
N_FIELDS: 0
 PAGE_NO: 3
   SPACE: 60
*************************** 2. row ***************************
INDEX_ID: 117
    NAME: i1
TABLE_ID: 74
    TYPE: 0
N_FIELDS: 1
 PAGE_NO: 4
   SPACE: 60

Notes

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

21.30.22 The INFORMATION_SCHEMA INNODB_SYS_TABLES Table

The INNODB_SYS_TABLES table provides metadata about InnoDB tables, equivalent to the information from the SYS_TABLES table in the InnoDB data dictionary.

For related usage information and examples, see Section 14.15.3, “InnoDB INFORMATION_SCHEMA System Tables”.

The INNODB_SYS_TABLES table has these columns:

  • TABLE_ID

    An identifier for the InnoDB table. This value is unique across all databases in the instance.

  • NAME

    The name of the table, preceded by the schema (database) name where appropriate; for example test/t1. Names of databases and user tables are in the same case as they were originally defined, possibly influenced by the lower_case_table_names setting.

  • FLAG

    A numeric value that represents bit-level information about table format and storage characteristics.

  • N_COLS

    The number of columns in the table. The number reported includes three hidden columns that are created by InnoDB (DB_ROW_ID, DB_TRX_ID, and DB_ROLL_PTR).

  • SPACE

    An identifier for the tablespace where the table resides. 0 means the InnoDB system tablespace. Any other number represents a table created in file-per-table mode with a separate .ibd file. This identifier stays the same after a TRUNCATE TABLE statement. Other than the zero value, this identifier is unique for tables across all the databases in the instance.

  • FILE_FORMAT

    The table's file format (Antelope or Barracuda).

  • ROW_FORMAT

    The table's row format (Compact, Redundant, Dynamic, or Compressed).

  • ZIP_PAGE_SIZE

    The zip page size. Applies only to tables with a row format of Compressed.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_TABLES WHERE TABLE_ID = 74\G
*************************** 1. row ***************************
     TABLE_ID: 74
         NAME: test/t1
         FLAG: 1
       N_COLS: 6
        SPACE: 60
  FILE_FORMAT: Antelope
   ROW_FORMAT: Compact
ZIP_PAGE_SIZE: 0

Notes

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

21.30.23 The INFORMATION_SCHEMA INNODB_SYS_TABLESPACES Table

The INNODB_SYS_TABLESPACES table provides metadata about InnoDB tablespaces, equivalent to the information in the SYS_TABLESPACES table in the InnoDB data dictionary.

For related usage information and examples, see Section 14.15.3, “InnoDB INFORMATION_SCHEMA System Tables”.

The INNODB_SYS_TABLESPACES table has these columns:

  • SPACE

    The tablespace ID.

  • NAME

    The schema (database) and table name.

  • FLAG

    A numeric value that represents bit-level information about tablespace format and storage characteristics.

  • FILE_FORMAT

    The tablespace file format (for example, Antelope or Barracuda). The data in this field is interpreted from the tablespace flags information that resides in the .ibd file. For more information about InnoDB file formats, see Section 14.10, “InnoDB File-Format Management”.

  • ROW_FORMAT

    The tablespace row format (Compact or Redundant, Dynamic, or Compressed). The data in this column is interpreted from the tablespace flags information that resides in the .ibd file.

  • PAGE_SIZE

    The tablespace page size. The data in this column is interpreted from the tablespace flags information that resides in the .ibd file.

  • ZIP_PAGE_SIZE

    The tablespace zip page size. The data in this column is interpreted from the tablespace flags information that resides in the .ibd file.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_TABLESPACES WHERE SPACE = 57\G
*************************** 1. row ***************************
        SPACE: 57
         NAME: test/t1
         FLAG: 0
  FILE_FORMAT: Antelope
   ROW_FORMAT: Compact or Redundant
    PAGE_SIZE: 16384
ZIP_PAGE_SIZE: 0

Notes

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

  • Because tablespace flags are always zero for all Antelope file formats (unlike table flags), there is no way to determine from this flag integer if the tablespace row format is Redundant or Compact. As a result, the possible values for the ROW_FORMAT field are Compact or Redundant, Compressed, or Dynamic.

21.30.24 The INFORMATION_SCHEMA INNODB_SYS_TABLESTATS View

The INNODB_SYS_TABLESTATS table provides a view of low-level status information about InnoDB tables. This data is used by the MySQL optimizer to calculate which index to use when querying an InnoDB table. This information is derived from in-memory data structures rather than data stored on disk. There is no corresponding internal InnoDB system table.

InnoDB tables are represented in this view if they have been opened since the last server restart and have not aged out of the table cache. Tables for which persistent stats are available are always represented in this view.

Table statistics are updated only for DELETE or UPDATE operations that modify indexed columns. Statistics are not updated by operations that modify only nonindexed columns.

For related usage information and examples, see Section 14.15.3, “InnoDB INFORMATION_SCHEMA System Tables”.

The INNODB_SYS_TABLESTATS table has these columns:

  • TABLE_ID

    An identifier representing the table for which statistics are available; the same value as INNODB_SYS_TABLES.TABLE_ID.

  • NAME

    The name of the table; the same value as INNODB_SYS_TABLES.NAME.

  • STATS_INITIALIZED

    The value is Initialized if the statistics are already collected, Uninitialized if not.

  • NUM_ROWS

    The current estimated number of rows in the table. Updated after each DML operation. The value could be imprecise if uncommitted transactions are inserting into or deleting from the table.

  • CLUST_INDEX_SIZE

    The number of pages on disk that store the clustered index, which holds the InnoDB table data in primary key order. This value might be null if no statistics are collected yet for the table.

  • OTHER_INDEX_SIZE

    The number of pages on disk that store all secondary indexes for the table. This value might be null if no statistics are collected yet for the table.

  • MODIFIED_COUNTER

    The number of rows modified by DML operations, such as INSERT, UPDATE, DELETE, and also cascade operations from foreign keys. This column is reset each time table statistics are recalculated

  • AUTOINC

    The next number to be issued for any auto-increment-based operation. The rate at which the AUTOINC value changes depends on how many times auto-increment numbers have been requested and how many numbers are granted per request.

  • REF_COUNT

    When this counter reaches zero, the table metadata can be evicted from the table cache.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_SYS_TABLESTATS where TABLE_ID = 71\G
*************************** 1. row ***************************
         TABLE_ID: 71
             NAME: test/t1
STATS_INITIALIZED: Initialized
         NUM_ROWS: 1
 CLUST_INDEX_SIZE: 1
 OTHER_INDEX_SIZE: 0
 MODIFIED_COUNTER: 1
          AUTOINC: 0
        REF_COUNT: 1

Notes

  • This table is useful primarily for expert-level performance monitoring, or when developing performance-related extensions for MySQL.

  • You must have the PROCESS privilege to query this table.

  • Use the INFORMATION_SCHEMA COLUMNS table or the SHOW COLUMNS statement to view additional information about the columns of this table, including data types and default values.

21.30.25 The INFORMATION_SCHEMA INNODB_TRX Table

The INNODB_TRX table provides information about every transaction (excluding read-only transactions) currently executing inside InnoDB, including whether the transaction is waiting for a lock, when the transaction started, and the SQL statement the transaction is executing, if any.

For usage information, see Section 14.15.2.1, “Using InnoDB Transaction and Locking Information”.

The INNODB_TRX table has these columns:

  • TRX_ID

    A unique transaction ID number, internal to InnoDB. (Starting in MySQL 5.6, these IDs are not created for transactions that are read only and nonlocking. For details, see Section 8.5.3, “Optimizing InnoDB Read-Only Transactions”.)

  • TRX_WEIGHT

    The weight of a transaction, reflecting (but not necessarily the exact count of) the number of rows altered and the number of rows locked by the transaction. To resolve a deadlock, InnoDB selects the transaction with the smallest weight as the victim to roll back. Transactions that have changed nontransactional tables are considered heavier than others, regardless of the number of altered and locked rows.

  • TRX_STATE

    The transaction execution state. Permitted values are RUNNING, LOCK WAIT, ROLLING BACK, and COMMITTING.

  • TRX_STARTED

    The transaction start time.

  • TRX_REQUESTED_LOCK_ID

    The ID of the lock the transaction is currently waiting for, if TRX_STATE is LOCK WAIT; otherwise NULL. To obtain details about the lock, join this column with the LOCK_ID column of the INNODB_LOCKS table.

  • TRX_WAIT_STARTED

    The time when the transaction started waiting on the lock, if TRX_STATE is LOCK WAIT; otherwise NULL.

  • TRX_MYSQL_THREAD_ID

    The MySQL thread ID. To obtain details about the thread, join this column with the ID column of the INFORMATION_SCHEMA PROCESSLIST table, but see Section 14.15.2.3, “Persistence and Consistency of InnoDB Transaction and Locking Information”.

  • TRX_QUERY

    The SQL statement that is being executed by the transaction.

  • TRX_OPERATION_STATE

    The transaction's current operation, if any; otherwise NULL.

  • TRX_TABLES_IN_USE

    The number of InnoDB tables used while processing the current SQL statement of this transaction.

  • TRX_TABLES_LOCKED

    The number of InnoDB tables that the current SQL statement has row locks on. (Because these are row locks, not table locks, the tables can usually still be read from and written to by multiple transactions, despite some rows being locked.)

  • TRX_LOCK_STRUCTS

    The number of locks reserved by the transaction.

  • TRX_LOCK_MEMORY_BYTES

    The total size taken up by the lock structures of this transaction in memory.

  • TRX_ROWS_LOCKED

    The approximate number or rows locked by this transaction. The value might include delete-marked rows that are physically present but not visible to the transaction.

  • TRX_ROWS_MODIFIED

    The number of modified and inserted rows in this transaction.

  • TRX_CONCURRENCY_TICKETS

    A value indicating how much work the current transaction can do before being swapped out, as specified by the innodb_concurrency_tickets system variable.

  • TRX_ISOLATION_LEVEL

    The isolation level of the current transaction.

  • TRX_UNIQUE_CHECKS

    Whether unique checks are turned on or off for the current transaction. For example, they might be turned off during a bulk data load.

  • TRX_FOREIGN_KEY_CHECKS

    Whether foreign key checks are turned on or off for the current transaction. For example, they might be turned off during a bulk data load.

  • TRX_LAST_FOREIGN_KEY_ERROR

    The detailed error message for the last foreign key error, if any; otherwise NULL.

  • TRX_ADAPTIVE_HASH_LATCHED

    Whether the adaptive hash index is locked by the current transaction. (Only a single transaction at a time can modify the adaptive hash index.)

  • TRX_ADAPTIVE_HASH_TIMEOUT

    Whether to relinquish the search latch immediately for the adaptive hash index, or reserve it across calls from MySQL. When there is no adaptive hash index contention, this value remains zero and statements reserve the latch until they finish. During times of contention, it counts down to zero, and statements release the latch immediately after each row lookup.

  • TRX_IS_READ_ONLY

    A value of 1 indicates the transaction is read only.

  • TRX_AUTOCOMMIT_NON_LOCKING

    A value of 1 indicates the transaction is a SELECT statement that does not use the FOR UPDATE or LOCK IN SHARED MODE clauses, and is executing with autocommit enabled so that the transaction will contain only this one statement. When this column and TRX_IS_READ_ONLY are both 1, InnoDB optimizes the transaction to reduce the overhead associated with transactions that change table data.

Example

mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_TRX\G
*************************** 1. row ***************************
                    trx_id: 3298
                 trx_state: RUNNING
               trx_started: 2014-11-19 13:54:39
     trx_requested_lock_id: NULL
          trx_wait_started: NULL
                trx_weight: 316436
       trx_mysql_thread_id: 2
                 trx_query: DELETE FROM employees.salaries WHERE salary > 65000
       trx_operation_state: updating or deleting
         trx_tables_in_use: 1
         trx_tables_locked: 1
          trx_lock_structs: 1621
     trx_lock_memory_bytes: 243240
           trx_rows_locked: 759343
         trx_rows_modified: 314815
   trx_concurrency_tickets: 0
       trx_isolation_level: REPEATABLE READ
         trx_unique_checks: 1
    trx_foreign_key_checks: 1
trx_last_foreign_key_error: NULL
 trx_adaptive_hash_latched: 0
 trx_adaptive_hash_timeout: 10000
          trx_is_read_only: 0
trx_autocommit_non_locking: 0

Notes

21.31 INFORMATION_SCHEMA NDB Cluster Tables

The following sections provide information about INFORMATION_SCHEMA tables which are specific to NDB Cluster. (The FILES table is available in standard MySQL 5.6 but is not used there.) The ndb_transid_mysql_connection_map table is implemented as an INFORMATION_SCHEMA plugin available only in NDB Cluster binaries or source, and does not exist in MySQL Server 5.6.

Additional statistical and other data about NDB Cluster transactions, operations, threads, blocks, and other aspects of performance can be obtained from the tables in the ndbinfo database. For information about these tables, see Section 18.5.10, “ndbinfo: The NDB Cluster Information Database”.

21.31.1 The INFORMATION_SCHEMA FILES Table

The FILES table provides information about the files in which MySQL NDB Disk Data tables are stored.

The FILES table has these columns:

  • FILE_ID

    A file identifier. FILE_ID column values are auto-generated.

  • FILE_NAME

    The name of an UNDO log file created by CREATE LOGFILE GROUP or ALTER LOGFILE GROUP, or of a data file created by CREATE TABLESPACE or ALTER TABLESPACE.

  • FILE_TYPE

    One of the values UNDO LOG, DATAFILE, or TABLESPACE.

  • TABLESPACE_NAME

    The name of the tablespace with which the file is associated.

  • TABLE_CATALOG

    This value is always empty.

  • TABLE_SCHEMA

    This value is always NULL.

  • TABLE_NAME

    The name of the Disk Data table with which the file is associated, if any.

  • LOGFILE_GROUP_NAME

    The name of the log file group to which the log file or data file belongs.

  • LOGFILE_GROUP_NUMBER

    For an UNDO log file, the auto-generated ID number of the log file group to which the log file belongs.

  • ENGINE

    For an NDB Cluster Disk Data log file or data file, this value always NDB or NDBCLUSTER.

  • FULLTEXT_KEYS

    For an NDB Cluster Disk Data log file or data file, this value is always empty.

  • DELETED_ROWS

    This value is always NULL.

  • UPDATE_COUNT

    This value is always NULL.

  • FREE_EXTENTS

    The number of extents which have not yet been used by the file.

  • TOTAL_EXTENTS

    The total number of extents allocated to the file.

  • EXTENT_SIZE

    The size of an extent for the file in bytes.

  • INITIAL_SIZE

    The size of the file in bytes. This is the same value that was used in the INITIAL_SIZE clause of the CREATE LOGFILE GROUP, ALTER LOGFILE GROUP, CREATE TABLESPACE, or ALTER TABLESPACE statement used to create the file.

  • MAXIMUM_SIZE

    For NDB Cluster Disk Data files, this value is always the same as the INITIAL_SIZE value.

  • AUTOEXTEND_SIZE

    For NDB Cluster Disk Data files, this value is always empty.

  • CREATION_TIME

    The date and time when the file was created.

  • LAST_UPDATE_TIME

    The date and time when the file was last modified.

  • LAST_ACCESS_TIME

    The date and time when the file was last accessed by the server.

  • RECOVER_TIME

    For NDB Cluster Disk Data files, this value is always 0.

  • TRANSACTION_COUNTER

    For NDB Cluster Disk Data files, this value is always 0.

  • VERSION

    For NDB Cluster Disk Data files, this value is always NULL.

  • ROW_FORMAT

    For NDB Cluster Disk Data files, this value is always NULL.

  • TABLE_ROWS

    For NDB Cluster Disk Data files, this value is always NULL.

  • AVG_ROW_LENGTH

    For NDB Cluster Disk Data files, this value is always NULL.

  • DATA_LENGTH

    For NDB Cluster Disk Data files, this value is always NULL.

  • MAX_DATA_LENGTH

    For NDB Cluster Disk Data files, this value is always NULL.

  • INDEX_LENGTH

    For NDB Cluster Disk Data files, this value is always NULL.

  • DATA_FREE

    For NDB Cluster Disk Data files, this value is always NULL.

  • CREATE_TIME

    For NDB Cluster Disk Data files, this value is always NULL.

  • UPDATE_TIME

    For NDB Cluster Disk Data files, this value is always NULL.

  • CHECK_TIME

    For NDB Cluster Disk Data files, this value is always NULL.

  • CHECKSUM

    For NDB Cluster Disk Data files, this value is always NULL.

  • STATUS

    For NDB Cluster Disk Data files, this value is always NORMAL.

  • EXTRA

    For NDB Cluster Disk Data files, the EXTRA column shows which data node the file belongs to (each data node having its own copy), as well as the size of its undo buffer. Suppose that you use this statement on an NDB Cluster with four data nodes:

    CREATE LOGFILE GROUP mygroup
        ADD UNDOFILE 'new_undo.dat'
        INITIAL_SIZE 2G
        ENGINE NDB;
    

    After running the CREATE LOGFILE GROUP statement successfully, you should see a result similar to the one shown here for this query against the FILES table:

    mysql> SELECT LOGFILE_GROUP_NAME, FILE_TYPE, EXTRA
             FROM INFORMATION_SCHEMA.FILES
             WHERE FILE_NAME = 'new_undo.dat';
    
    +--------------------+-----------+-----------------------------------------+
    | LOGFILE_GROUP_NAME | FILE_TYPE | EXTRA                                   |
    +--------------------+-----------+-----------------------------------------+
    | mygroup            | UNDO LOG  | CLUSTER_NODE=5;UNDO_BUFFER_SIZE=8388608 |
    | mygroup            | UNDO LOG  | CLUSTER_NODE=6;UNDO_BUFFER_SIZE=8388608 |
    | mygroup            | UNDO LOG  | CLUSTER_NODE=7;UNDO_BUFFER_SIZE=8388608 |
    | mygroup            | UNDO LOG  | CLUSTER_NODE=8;UNDO_BUFFER_SIZE=8388608 |
    +--------------------+-----------+-----------------------------------------+
    

Notes

  • The FILES table is a nonstandard INFORMATION_SCHEMA table.

NDB Notes

  • This table provides information about Disk Data files only; you cannot use it for determining disk space allocation or availability for individual NDB tables. However, it is possible to see how much space is allocated for each NDB table having data stored on disk—as well as how much remains available for storage of data on disk for that table—using ndb_desc. For more information, see Section 18.4.10, “ndb_desc — Describe NDB Tables”.

  • The CREATION_TIME, LAST_UPDATE_TIME, and LAST_ACCESSED values are as reported by the operating system, and are not supplied by the NDB storage engine. Where no value is provided by the operating system, these columns display 0000-00-00 00:00:00.

  • The difference between the TOTAL EXTENTS and FREE_EXTENTS columns is the number of extents currently in use by the file:

    SELECT TOTAL_EXTENTS - FREE_EXTENTS AS extents_used
        FROM INFORMATION_SCHEMA.FILES
        WHERE FILE_NAME = 'myfile.dat';
    

    To approximate the amount of disk space in use by the file, multiply that difference by the value of the EXTENT_SIZE column, which gives the size of an extent for the file in bytes:

    SELECT (TOTAL_EXTENTS - FREE_EXTENTS) * EXTENT_SIZE AS bytes_used
        FROM INFORMATION_SCHEMA.FILES
        WHERE FILE_NAME = 'myfile.dat';
    

    Similarly, you can estimate the amount of space that remains available in a given file by multiplying FREE_EXTENTS by EXTENT_SIZE:

    SELECT FREE_EXTENTS * EXTENT_SIZE AS bytes_free
        FROM INFORMATION_SCHEMA.FILES
        WHERE FILE_NAME = 'myfile.dat';
    
    Important

    The byte values produced by the preceding queries are approximations only, and their precision is inversely proportional to the value of EXTENT_SIZE. That is, the larger EXTENT_SIZE becomes, the less accurate the approximations are.

    It is also important to remember that once an extent is used, it cannot be freed again without dropping the data file of which it is a part. This means that deletes from a Disk Data table do not release disk space.

    The extent size can be set in a CREATE TABLESPACE statement. For more information, see Section 13.1.18, “CREATE TABLESPACE Syntax”.

  • An additional row is present in the FILES table following the creation of a logfile group. This row has NULL for the value of the FILE_NAME column. For this row, the value of the FILE_ID column is always 0, that of the FILE_TYPE column is always UNDO LOG, and that of the STATUS column is always NORMAL. The value of the ENGINE column is always NDBCLUSTER.

    The FREE_EXTENTS column in this row shows the total number of free extents available to all undo files belonging to a given log file group whose name and number are shown in the LOGFILE_GROUP_NAME and LOGFILE_GROUP_NUMBER columns, respectively.

    Suppose there are no existing log file groups on your NDB Cluster, and you create one using the following statement:

    mysql> CREATE LOGFILE GROUP lg1
             ADD UNDOFILE 'undofile.dat'
             INITIAL_SIZE = 16M
             UNDO_BUFFER_SIZE = 1M
             ENGINE = NDB;
    

    You can now see this NULL row when you query the FILES table:

    mysql> SELECT DISTINCT
             FILE_NAME AS File,
             FREE_EXTENTS AS Free,
             TOTAL_EXTENTS AS Total,
             EXTENT_SIZE AS Size,
             INITIAL_SIZE AS Initial
             FROM INFORMATION_SCHEMA.FILES;
    +--------------+---------+---------+------+----------+
    | File         | Free    | Total   | Size | Initial  |
    +--------------+---------+---------+------+----------+
    | undofile.dat |    NULL | 4194304 |    4 | 16777216 |
    | NULL         | 4184068 |    NULL |    4 |     NULL |
    +--------------+---------+---------+------+----------+
    

    The total number of free extents available for undo logging is always somewhat less than the sum of the TOTAL_EXTENTS column values for all undo files in the log file group due to overhead required for maintaining the undo files. This can be seen by adding a second undo file to the log file group, then repeating the previous query against the FILES table:

    mysql> ALTER LOGFILE GROUP lg1
             ADD UNDOFILE 'undofile02.dat'
             INITIAL_SIZE = 4M
             ENGINE = NDB;
    
    mysql> SELECT DISTINCT
             FILE_NAME AS File,
             FREE_EXTENTS AS Free,
             TOTAL_EXTENTS AS Total,
             EXTENT_SIZE AS Size,
             INITIAL_SIZE AS Initial
             FROM INFORMATION_SCHEMA.FILES;
    +----------------+---------+---------+------+----------+
    | File           | Free    | Total   | Size | Initial  |
    +----------------+---------+---------+------+----------+
    | undofile.dat   |    NULL | 4194304 |    4 | 16777216 |
    | undofile02.dat |    NULL | 1048576 |    4 |  4194304 |
    | NULL           | 5223944 |    NULL |    4 |     NULL |
    +----------------+---------+---------+------+----------+
    

    The amount of free space in bytes which is available for undo logging by Disk Data tables using this log file group can be approximated by multiplying the number of free extents by the initial size:

    mysql> SELECT
             FREE_EXTENTS AS 'Free Extents',
             FREE_EXTENTS * EXTENT_SIZE AS 'Free Bytes'
             FROM INFORMATION_SCHEMA.FILES
             WHERE LOGFILE_GROUP_NAME = 'lg1'
             AND FILE_NAME IS NULL;
    +--------------+------------+
    | Free Extents | Free Bytes |
    +--------------+------------+
    |      5223944 |   20895776 |
    +--------------+------------+
    

    If you create an NDB Cluster Disk Data table and then insert some rows into it, you can see approximately how much space remains for undo logging afterward, for example:

    mysql> CREATE TABLESPACE ts1
             ADD DATAFILE 'data1.dat'
             USE LOGFILE GROUP lg1
             INITIAL_SIZE 512M
             ENGINE = NDB;
    
    mysql> CREATE TABLE dd (
             c1 INT NOT NULL PRIMARY KEY,
             c2 INT,
             c3 DATE
             )
             TABLESPACE ts1 STORAGE DISK
             ENGINE = NDB;
    
    mysql> INSERT INTO dd VALUES
             (NULL, 1234567890, '2007-02-02'),
             (NULL, 1126789005, '2007-02-03'),
             (NULL, 1357924680, '2007-02-04'),
             (NULL, 1642097531, '2007-02-05');
    
    mysql> SELECT
             FREE_EXTENTS AS 'Free Extents',
             FREE_EXTENTS * EXTENT_SIZE AS 'Free Bytes'
             FROM INFORMATION_SCHEMA.FILES
             WHERE LOGFILE_GROUP_NAME = 'lg1'
             AND FILE_NAME IS NULL;
    +--------------+------------+
    | Free Extents | Free Bytes |
    +--------------+------------+
    |      5207565 |   20830260 |
    +--------------+------------+
    
  • An additional row is present in the FILES table for any NDB Cluster tablespace, whether or not any data files are associated with the tablespace. This row has NULL for the value of the FILE_NAME column. For this row, the value of the FILE_ID column is always 0, that of the FILE_TYPE column is always TABLESPACE, and that of the STATUS column is always NORMAL. The value of the ENGINE column is always NDBCLUSTER.

  • For additional information, and examples of creating and dropping NDB Cluster Disk Data objects, see Section 18.5.12, “NDB Cluster Disk Data Tables”.

21.31.2 The INFORMATION_SCHEMA ndb_transid_mysql_connection_map Table

The ndb_transid_mysql_connection_map table provides a mapping between NDB transactions, NDB transaction coordinators, and MySQL Servers attached to an NDB Cluster as API nodes. This information is used when populating the server_operations and server_transactions tables of the ndbinfo NDB Cluster information database.

The ndb_transid_mysql_connection_map table has these columns:

  • mysql_connection_id

    The MySQL server connection ID.

  • node_id

    The transaction coordinator node ID.

  • ndb_transid

    The NDB transaction ID.

Notes

The mysql_connection_id value is the same as the connection or session ID shown in the output of SHOW PROCESSLIST.

There are no SHOW statements associated with this table.

This is a nonstandard table, specific to NDB Cluster. It is implemented as an INFORMATION_SCHEMA plugin; you can verify that it is supported by checking the output of SHOW PLUGINS. If ndb_transid_mysql_connection_map support is enabled, the output from this statement includes a plugin having this name, of type INFORMATION SCHEMA, and having status ACTIVE, as shown here (using emphasized text):

mysql> SHOW PLUGINS;
+----------------------------------+--------+--------------------+---------+---------+
| Name                             | Status | Type               | Library | License |
+----------------------------------+--------+--------------------+---------+---------+
| binlog                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| mysql_native_password            | ACTIVE | AUTHENTICATION     | NULL    | GPL     |
| mysql_old_password               | ACTIVE | AUTHENTICATION     | NULL    | GPL     |
| CSV                              | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| MEMORY                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| MRG_MYISAM                       | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| MyISAM                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| PERFORMANCE_SCHEMA               | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| BLACKHOLE                        | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ARCHIVE                          | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ndbcluster                       | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ndbinfo                          | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| ndb_transid_mysql_connection_map | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| InnoDB                           | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
| INNODB_TRX                       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_LOCKS                     | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_LOCK_WAITS                | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMP                       | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMP_RESET                 | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMPMEM                    | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| INNODB_CMPMEM_RESET              | ACTIVE | INFORMATION SCHEMA | NULL    | GPL     |
| partition                        | ACTIVE | STORAGE ENGINE     | NULL    | GPL     |
+----------------------------------+--------+--------------------+---------+---------+
22 rows in set (0.00 sec)

The plugin is enabled by default. You can disable it (or force the server not to run unless the plugin starts) by starting the server with the --ndb-transid-mysql-connection-map option. If the plugin is disabled, the status is shown by SHOW PLUGINS as DISABLED. The plugin cannot be enabled or disabled at runtime.

Although the names of this table and its columns are displayed using lowercase, you can use uppercase or lowercase when referring to them in SQL statements.

For this table to be created, the MySQL Server must be a binary supplied with the NDB Cluster distribution, or one built from the NDB Cluster sources with NDB storage engine support enabled. It is not available in the standard MySQL 5.6 Server.

21.32 INFORMATION_SCHEMA Thread Pool Tables

The following sections describe the INFORMATION_SCHEMA tables associated with the thread pool plugin (see Section 5.5.3, “MySQL Enterprise Thread Pool”). They provide information about thread pool operation:

Rows in these tables represent snapshots in time. In the case of TP_THREAD_STATE, all rows for a thread group comprise a snapshot in time. Thus, the MySQL server holds the mutex of the thread group while producing the snapshot. But it does not hold mutexes on all thread groups at the same time, to prevent a statement against TP_THREAD_STATE from blocking the entire MySQL server.

The thread pool INFORMATION_SCHEMA tables are implemented by individual plugins and the decision whether to load one can be made independently of the others (see Section 5.5.3.2, “Thread Pool Installation”). However, the content of all the tables depends on the thread pool plugin being enabled. If a table plugin is enabled but the thread pool plugin is not, the table becomes visible and can be accessed but will be empty.

21.32.1 The INFORMATION_SCHEMA TP_THREAD_GROUP_STATE Table

The TP_THREAD_GROUP_STATE table has one row per thread group in the thread pool. Each row provides information about the current state of a group.

The TP_THREAD_GROUP_STATE table has these columns:

  • TP_GROUP_ID

    The thread group ID. This is a unique key within the table.

  • CONSUMER THREADS

    The number of consumer threads. There is at most one thread ready to start executing if the active threads become stalled or blocked.

  • RESERVE_THREADS

    The number of threads in the reserved state. This means that they will not be started until there is a need to wake a new thread and there is no consumer thread. This is where most threads end up when the thread group has created more threads than needed for normal operation. Often a thread group needs additional threads for a short while and then does not need them again for a while. In this case, they go into the reserved state and remain until needed again. They take up some extra memory resources, but no extra computing resources.

  • CONNECT_THREAD_COUNT

    The number of threads that are processing or waiting to process connection initialization and authentication. There can be a maximum of four connection threads per thread group; these threads expire after a period of inactivity.

    This column was added in MySQL 5.6.36.

  • CONNECTION_COUNT

    The number of connections using this thread group.

  • QUEUED_QUERIES

    The number of statements waiting in the high-priority queue.

  • QUEUED_TRANSACTIONS

    The number of statements waiting in the low-priority queue. These are the initial statements for transactions that have not started, so they also represent queued transactions.

  • STALL_LIMIT

    The value of the thread_pool_stall_limit system variable for the thread group. This is the same value for all thread groups.

  • PRIO_KICKUP_TIMER

    The value of the thread_pool_prio_kickup_timer system variable for the thread group. This is the same value for all thread groups.

  • ALGORITHM

    The value of the thread_pool_algorithm system variable for the thread group. This is the same value for all thread groups.

  • THREAD_COUNT

    The number of threads started in the thread pool as part of this thread group.

  • ACTIVE_THREAD_COUNT

    The number of threads active in executing statements.

  • STALLED_THREAD_COUNT

    The number of stalled statements in the thread group. A stalled statement could be executing, but from a thread pool perspective it is stalled and making no progress. A long-running statement quickly ends up in this category.

  • WAITING_THREAD_NUMBER

    If there is a thread handling the polling of statements in the thread group, this specifies the thread number within this thread group. It is possible that this thread could be executing a statement.

  • OLDEST_QUEUED

    How long in milliseconds the oldest queued statement has been waiting for execution.

  • MAX_THREAD_IDS_IN_GROUP

    The maximum thread ID of the threads in the group. This is the same as MAX(TP_THREAD_NUMBER) for the threads when selected from the TP_THREAD_STATE table. That is, these two queries are equivalent:

    SELECT TP_GROUP_ID, MAX_THREAD_IDS_IN_GROUP
    FROM TP_THREAD_GROUP_STATE;
    
    SELECT TP_GROUP_ID, MAX(TP_THREAD_NUMBER)
    FROM TP_THREAD_STATE GROUP BY TP_GROUP_ID;
    

21.32.2 The INFORMATION_SCHEMA TP_THREAD_GROUP_STATS Table

The TP_THREAD_GROUP_STATS table reports statistics per thread group. There is one row per group.

The TP_THREAD_GROUP_STATS table has these columns:

  • TP_GROUP_ID

    The thread group ID. This is a unique key within the table.

  • CONNECTIONS_STARTED

    The number of connections started.

  • CONNECTIONS_CLOSED

    The number of connections closed.

  • QUERIES_EXECUTED

    The number of statements executed. This number is incremented when a statement starts executing, not when it finishes.

  • QUERIES_QUEUED

    The number of statements received that were queued for execution. This does not count statements that the thread group was able to begin executing immediately without queuing, which can happen under the conditions described in Section 5.5.3.3, “Thread Pool Operation”.

  • THREADS_STARTED

    The number of threads started.

  • PRIO_KICKUPS

    The number of statements that have been moved from low-priority queue to high-priority queue based on the value of the thread_pool_prio_kickup_timer system variable. If this number increases quickly, consider increasing the value of that variable. A quickly increasing counter means that the priority system is not keeping transactions from starting too early. For InnoDB, this most likely means deteriorating performance due to too many concurrent transactions..

  • STALLED_QUERIES_EXECUTED

    The number of statements that have become defined as stalled due to executing for longer than the value of the thread_pool_stall_limit system variable.

  • BECOME_CONSUMER_THREAD

    The number of times thread have been assigned the consumer thread role.

  • BECOME_RESERVE_THREAD

    The number of times threads have been assigned the reserve thread role.

  • BECOME_WAITING_THREAD

    The number of times threads have been assigned the waiter thread role. When statements are queued, this happens very often, even in normal operation, so rapid increases in this value are normal in the case of a highly loaded system where statements are queued up.

  • WAKE_THREAD_STALL_CHECKER

    The number of times the stall check thread decided to wake or create a thread to possibly handle some statements or take care of the waiter thread role.

  • SLEEP_WAITS

    The number of THD_WAIT_SLEEP waits. These occur when threads go to sleep; for example, by calling the SLEEP() function.

  • DISK_IO_WAITS

    The number of THD_WAIT_DISKIO waits. These occur when threads perform disk I/O that is likely to not hit the file system cache. Such waits occur when the buffer pool reads and writes data to disk, not for normal reads from and writes to files.

  • ROW_LOCK_WAITS

    The number of THD_WAIT_ROW_LOCK waits for release of a row lock by another transaction.

  • GLOBAL_LOCK_WAITS

    The number of THD_WAIT_GLOBAL_LOCK waits for a global lock to be released.

  • META_DATA_LOCK_WAITS

    The number of THD_WAIT_META_DATA_LOCK waits for a metadata lock to be released.

  • TABLE_LOCK_WAITS

    The number of THD_WAIT_TABLE_LOCK waits for a table to be unlocked that the statement needs to access.

  • USER_LOCK_WAITS

    The number of THD_WAIT_USER_LOCK waits for a special lock constructed by the user thread.

  • BINLOG_WAITS

    The number of THD_WAIT_BINLOG_WAITS waits for the binary log to become free.

  • GROUP_COMMIT_WAITS

    The number of THD_WAIT_GROUP_COMMIT waits. These occur when a group commit must wait for the other parties to complete their part of a transaction.

  • FSYNC_WAITS

    The number of THD_WAIT_SYNC waits for a file sync operation.

21.32.3 The INFORMATION_SCHEMA TP_THREAD_STATE Table

The TP_THREAD_STATE table has one row per thread created by the thread pool to handle connections.

The TP_THREAD_STATE table has these columns:

  • TP_GROUP_ID

    The thread group ID.

  • TP_THREAD_NUMBER

    The ID of the thread within its thread group. TP_GROUP_ID and TP_THREAD_NUMBER together provide a unique key within the table.

  • PROCESS_COUNT

    The 10ms interval in which the statement that uses this thread is currently executing. 0 means no statement is executing, 1 means it is in the first 10ms, and so forth.

  • WAIT_TYPE

    The type of wait for the thread. NULL means the thread is not blocked. Otherwise, the thread is blocked by a call to thd_wait_begin() and the value specifies the type of wait. The xxx_WAIT columns of the TP_THREAD_GROUP_STATS table accumulate counts for each wait type.

    The WAIT_TYPE value is a string that describes the type of wait, as shown in the following table.

    Table 21.4 TP_THREAD_STATE Table WAIT_TYPE Values

    Wait Type Meaning
    THD_WAIT_SLEEP Waiting for sleep
    THD_WAIT_DISKIO Waiting for Disk IO
    THD_WAIT_ROW_LOCK Waiting for row lock
    THD_WAIT_GLOBAL_LOCK Waiting for global lock
    THD_WAIT_META_DATA_LOCK Waiting for metadata lock
    THD_WAIT_TABLE_LOCK Waiting for table lock
    THD_WAIT_USER_LOCK Waiting for user lock
    THD_WAIT_BINLOG Waiting for binlog
    THD_WAIT_GROUP_COMMIT Waiting for group commit
    THD_WAIT_SYNC Waiting for fsync

21.33 INFORMATION_SCHEMA Connection-Control Tables

The following sections describe the INFORMATION_SCHEMA tables associated with the CONNECTION_CONTROL plugin.

21.33.1 The INFORMATION_SCHEMA CONNECTION_CONTROL_FAILED_LOGIN_ATTEMPTS Table

This table provides information about the current number of consecutive failed connection attempts per client user/host combination. The table was added in MySQL 5.6.35.

CONNECTION_CONTROL_FAILED_LOGIN_ATTEMPTS has these columns:

  • USERHOST

    The user/host combination of a client that has failed connection attempts, in 'user_name'@'host_name' format.

  • FAILED_ATTEMPTS

    The current number of consecutive failed connection attempts for the USERHOST value. This counts all failed attempts, regardless of whether they were delayed. The number of attempts for which the server added a delay to its response is the difference between the FAILED_ATTEMPTS value and the connection_control_failed_connections_threshold system variable value.

Notes

  • The CONNECTION_CONTROL_FAILED_LOGIN_ATTEMPTS plugin must be activated for this table to be available, and the CONNECTION_CONTROL plugin must be activated or the table contents will always be empty. See Section 6.5.2, “The Connection-Control Plugins”.

  • The table contains rows only for clients that have had one or more consecutive failed connection attempts without a subsequent successful attempt. When a client connects successfully, its failed-connection count is reset to zero and the server removes any row corresponding to the client.

  • Assigning a value to the connection_control_failed_connections_threshold system variable at runtime resets all accumulated failed-connection counters to zero, which causes the table to become empty.

21.34 Extensions to SHOW Statements

Some extensions to SHOW statements accompany the implementation of INFORMATION_SCHEMA:

  • SHOW can be used to get information about the structure of INFORMATION_SCHEMA itself.

  • Several SHOW statements accept a WHERE clause that provides more flexibility in specifying which rows to display.

INFORMATION_SCHEMA is an information database, so its name is included in the output from SHOW DATABASES. Similarly, SHOW TABLES can be used with INFORMATION_SCHEMA to obtain a list of its tables:

mysql> SHOW TABLES FROM INFORMATION_SCHEMA;
+---------------------------------------+
| Tables_in_INFORMATION_SCHEMA          |
+---------------------------------------+
| CHARACTER_SETS                        |
| COLLATIONS                            |
| COLLATION_CHARACTER_SET_APPLICABILITY |
| COLUMNS                               |
| COLUMN_PRIVILEGES                     |
| ENGINES                               |
| EVENTS                                |
| FILES                                 |
| GLOBAL_STATUS                         |
| GLOBAL_VARIABLES                      |
| KEY_COLUMN_USAGE                      |
| PARTITIONS                            |
| PLUGINS                               |
| PROCESSLIST                           |
| REFERENTIAL_CONSTRAINTS               |
| ROUTINES                              |
| SCHEMATA                              |
| SCHEMA_PRIVILEGES                     |
| SESSION_STATUS                        |
| SESSION_VARIABLES                     |
| STATISTICS                            |
| TABLES                                |
| TABLE_CONSTRAINTS                     |
| TABLE_PRIVILEGES                      |
| TRIGGERS                              |
| USER_PRIVILEGES                       |
| VIEWS                                 |
+---------------------------------------+

SHOW COLUMNS and DESCRIBE can display information about the columns in individual INFORMATION_SCHEMA tables.

SHOW statements that accept a LIKE clause to limit the rows displayed also permit a WHERE clause that specifies more general conditions that selected rows must satisfy:

SHOW CHARACTER SET
SHOW COLLATION
SHOW COLUMNS
SHOW DATABASES
SHOW FUNCTION STATUS
SHOW INDEX
SHOW OPEN TABLES
SHOW PROCEDURE STATUS
SHOW STATUS
SHOW TABLE STATUS
SHOW TABLES
SHOW TRIGGERS
SHOW VARIABLES

The WHERE clause, if present, is evaluated against the column names displayed by the SHOW statement. For example, the SHOW CHARACTER SET statement produces these output columns:

mysql> SHOW CHARACTER SET;
+----------+-----------------------------+---------------------+--------+
| Charset  | Description                 | Default collation   | Maxlen |
+----------+-----------------------------+---------------------+--------+
| big5     | Big5 Traditional Chinese    | big5_chinese_ci     |      2 |
| dec8     | DEC West European           | dec8_swedish_ci     |      1 |
| cp850    | DOS West European           | cp850_general_ci    |      1 |
| hp8      | HP West European            | hp8_english_ci      |      1 |
| koi8r    | KOI8-R Relcom Russian       | koi8r_general_ci    |      1 |
| latin1   | cp1252 West European        | latin1_swedish_ci   |      1 |
| latin2   | ISO 8859-2 Central European | latin2_general_ci   |      1 |
...

To use a WHERE clause with SHOW CHARACTER SET, you would refer to those column names. As an example, the following statement displays information about character sets for which the default collation contains the string 'japanese':

mysql> SHOW CHARACTER SET WHERE `Default collation` LIKE '%japanese%';
+---------+---------------------------+---------------------+--------+
| Charset | Description               | Default collation   | Maxlen |
+---------+---------------------------+---------------------+--------+
| ujis    | EUC-JP Japanese           | ujis_japanese_ci    |      3 |
| sjis    | Shift-JIS Japanese        | sjis_japanese_ci    |      2 |
| cp932   | SJIS for Windows Japanese | cp932_japanese_ci   |      2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci |      3 |
+---------+---------------------------+---------------------+--------+

This statement displays the multibyte character sets:

mysql> SHOW CHARACTER SET WHERE Maxlen > 1;
+---------+---------------------------+---------------------+--------+
| Charset | Description               | Default collation   | Maxlen |
+---------+---------------------------+---------------------+--------+
| big5    | Big5 Traditional Chinese  | big5_chinese_ci     |      2 |
| ujis    | EUC-JP Japanese           | ujis_japanese_ci    |      3 |
| sjis    | Shift-JIS Japanese        | sjis_japanese_ci    |      2 |
| euckr   | EUC-KR Korean             | euckr_korean_ci     |      2 |
| gb2312  | GB2312 Simplified Chinese | gb2312_chinese_ci   |      2 |
| gbk     | GBK Simplified Chinese    | gbk_chinese_ci      |      2 |
| utf8    | UTF-8 Unicode             | utf8_general_ci     |      3 |
| ucs2    | UCS-2 Unicode             | ucs2_general_ci     |      2 |
| cp932   | SJIS for Windows Japanese | cp932_japanese_ci   |      2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci |      3 |
+---------+---------------------------+---------------------+--------+