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Chapter 19. INFORMATION_SCHEMA Tables

Table of Contents

19.1. The INFORMATION_SCHEMA CHARACTER_SETS Table
19.2. The INFORMATION_SCHEMA COLLATIONS Table
19.3. The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table
19.4. The INFORMATION_SCHEMA COLUMNS Table
19.5. The INFORMATION_SCHEMA COLUMN_PRIVILEGES Table
19.6. The INFORMATION_SCHEMA ENGINES Table
19.7. The INFORMATION_SCHEMA EVENTS Table
19.8. The INFORMATION_SCHEMA FILES Table
19.9. The INFORMATION_SCHEMA GLOBAL_STATUS and SESSION_STATUS Tables
19.10. The INFORMATION_SCHEMA GLOBAL_VARIABLES and SESSION_VARIABLES Tables
19.11. The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table
19.12. The INFORMATION_SCHEMA OPTIMIZER_TRACE Table
19.13. The INFORMATION_SCHEMA PARAMETERS Table
19.14. The INFORMATION_SCHEMA PARTITIONS Table
19.15. The INFORMATION_SCHEMA PLUGINS Table
19.16. The INFORMATION_SCHEMA PROCESSLIST Table
19.17. The INFORMATION_SCHEMA PROFILING Table
19.18. The INFORMATION_SCHEMA REFERENTIAL_CONSTRAINTS Table
19.19. The INFORMATION_SCHEMA ROUTINES Table
19.20. The INFORMATION_SCHEMA SCHEMATA Table
19.21. The INFORMATION_SCHEMA SCHEMA_PRIVILEGES Table
19.22. The INFORMATION_SCHEMA STATISTICS Table
19.23. The INFORMATION_SCHEMA TABLES Table
19.24. The INFORMATION_SCHEMA TABLESPACES Table
19.25. The INFORMATION_SCHEMA TABLE_CONSTRAINTS Table
19.26. The INFORMATION_SCHEMA TABLE_PRIVILEGES Table
19.27. The INFORMATION_SCHEMA TRIGGERS Table
19.28. The INFORMATION_SCHEMA USER_PRIVILEGES Table
19.29. The INFORMATION_SCHEMA VIEWS Table
19.30. INFORMATION_SCHEMA Tables for InnoDB
19.30.1. The INFORMATION_SCHEMA INNODB_CMP and INNODB_CMP_RESET Tables
19.30.2. The INFORMATION_SCHEMA INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET Tables
19.30.3. The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables
19.30.4. The INFORMATION_SCHEMA INNODB_TRX Table
19.30.5. The INFORMATION_SCHEMA INNODB_LOCKS Table
19.30.6. The INFORMATION_SCHEMA INNODB_LOCK_WAITS Table
19.30.7. The INFORMATION_SCHEMA INNODB_SYS_TABLES Table
19.30.8. The INFORMATION_SCHEMA INNODB_SYS_INDEXES Table
19.30.9. The INFORMATION_SCHEMA INNODB_SYS_COLUMNS Table
19.30.10. The INFORMATION_SCHEMA INNODB_SYS_FIELDS Table
19.30.11. The INFORMATION_SCHEMA INNODB_SYS_FOREIGN Table
19.30.12. The INFORMATION_SCHEMA INNODB_SYS_FOREIGN_COLS Table
19.30.13. The INFORMATION_SCHEMA INNODB_SYS_TABLESTATS View
19.30.14. The INFORMATION_SCHEMA INNODB_BUFFER_PAGE Table
19.30.15. The INFORMATION_SCHEMA INNODB_BUFFER_PAGE_LRU Table
19.30.16. The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table
19.30.17. The INFORMATION_SCHEMA INNODB_METRICS Table
19.30.18. The INFORMATION_SCHEMA INNODB_FT_CONFIG Table
19.30.19. The INFORMATION_SCHEMA INNODB_FT_DEFAULT_STOPWORD Table
19.30.20. The INFORMATION_SCHEMA INNODB_FT_INDEX_TABLE Table
19.30.21. The INFORMATION_SCHEMA INNODB_FT_INDEX_CACHE Table
19.30.22. The INFORMATION_SCHEMA INNODB_FT_INSERTED Table
19.30.23. The INFORMATION_SCHEMA INNODB_FT_DELETED Table
19.30.24. The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table
19.31. Thread Pool INFORMATION_SCHEMA Tables
19.31.1. The INFORMATION_SCHEMA TP_THREAD_STATE Table
19.31.2. The INFORMATION_SCHEMA TP_THREAD_GROUP_STATE Table
19.31.3. The INFORMATION_SCHEMA TP_THREAD_GROUP_STATS Table
19.32. 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.

Usage Notes for the INFORMATION_SCHEMA Database

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.

Example

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 10.1.7.9, “Collation and 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:

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 19.32, “Extensions to SHOW Statements”.

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 8.2.4, “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 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: http://web.archive.org/web/20070409075643rn_1/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:

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.

For information about INFORMATION_SCHEMA tables specific to the InnoDB storage engine, see Section 19.30, “INFORMATION_SCHEMA Tables for InnoDB. For information about INFORMATION_SCHEMA tables specific to the thread pool plugin, see Section 19.31, “Thread Pool INFORMATION_SCHEMA Tables”.

For answers to questions that are often asked concerning the INFORMATION_SCHEMA database, see Section B.7, “MySQL 5.6 FAQ: INFORMATION_SCHEMA.

19.1. The INFORMATION_SCHEMA CHARACTER_SETS Table

The CHARACTER_SETS table provides information about available character sets.

INFORMATION_SCHEMA NameSHOW NameRemarks
CHARACTER_SET_NAMECharset 
DEFAULT_COLLATE_NAMEDefault collation 
DESCRIPTIONDescriptionMySQL extension
MAXLENMaxlenMySQL extension

The following statements are equivalent:

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

SHOW CHARACTER SET
  [LIKE 'wild']

19.2. The INFORMATION_SCHEMA COLLATIONS Table

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

INFORMATION_SCHEMA NameSHOW NameRemarks
COLLATION_NAMECollation 
CHARACTER_SET_NAMECharsetMySQL extension
IDIdMySQL extension
IS_DEFAULTDefaultMySQL extension
IS_COMPILEDCompiledMySQL extension
SORTLENSortlenMySQL extension
  • COLLATION_NAME is the collation name.

  • CHARACTER_SET_NAME is the name of the character set with which the collation is associated.

  • ID is the collation ID.

  • IS_DEFAULT indicates whether the collation is the default for its character set.

  • IS_COMPILED indicates whether the character set is compiled into the server.

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

Collation information is also available from the SHOW COLLATION statement. The following statements are equivalent:

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

SHOW COLLATION
  [LIKE 'wild']

19.3. The INFORMATION_SCHEMA COLLATION_CHARACTER_SET_APPLICABILITY Table

The COLLATION_CHARACTER_SET_APPLICABILITY table indicates what character set is applicable for what collation. The columns are equivalent to the first two display fields that we get from SHOW COLLATION.

INFORMATION_SCHEMA NameSHOW NameRemarks
COLLATION_NAMECollation 
CHARACTER_SET_NAMECharset 

19.4. The INFORMATION_SCHEMA COLUMNS Table

The COLUMNS table provides information about columns in tables.

INFORMATION_SCHEMA NameSHOW NameRemarks
TABLE_CATALOG def
TABLE_SCHEMA  
TABLE_NAME  
COLUMN_NAMEField 
ORDINAL_POSITION see notes
COLUMN_DEFAULTDefault 
IS_NULLABLENull 
DATA_TYPEType 
CHARACTER_MAXIMUM_LENGTHType 
CHARACTER_OCTET_LENGTH  
NUMERIC_PRECISIONType 
NUMERIC_SCALEType 
DATETIME_PRECISIONType 
CHARACTER_SET_NAME  
COLLATION_NAMECollation 
COLUMN_TYPETypeMySQL extension
COLUMN_KEYKeyMySQL extension
EXTRAExtraMySQL extension
PRIVILEGESPrivilegesMySQL extension
COLUMN_COMMENTCommentMySQL extension

Notes:

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

  • ORDINAL_POSITION is necessary because you might want to say ORDER BY ORDINAL_POSITION. Unlike SHOW, SELECT does not have automatic ordering.

  • CHARACTER_OCTET_LENGTH should be the same as CHARACTER_MAXIMUM_LENGTH, except for multi-byte character sets.

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

  • DATETIME_PRECISION was added in MySQL 5.6.4.

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']

19.5. The INFORMATION_SCHEMA COLUMN_PRIVILEGES Table

The COLUMN_PRIVILEGES table provides information about column privileges. This information comes from the mysql.columns_priv grant table.

INFORMATION_SCHEMA NameSHOW NameRemarks
GRANTEE 'user_name'@'host_name' value
TABLE_CATALOG def
TABLE_SCHEMA  
TABLE_NAME  
COLUMN_NAME  
PRIVILEGE_TYPE  
IS_GRANTABLE  

Notes:

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

  • PRIVILEGE_TYPE can contain one (and only one) of these values: SELECT, INSERT, UPDATE, REFERENCES.

  • If the user has GRANT OPTION privilege, IS_GRANTABLE should be YES. Otherwise, IS_GRANTABLE should be NO. The output does not list GRANT OPTION as a separate privilege.

The following statements are not equivalent:

SELECT ... FROM INFORMATION_SCHEMA.COLUMN_PRIVILEGES

SHOW GRANTS ...

19.6. The INFORMATION_SCHEMA ENGINES Table

The ENGINES table provides information about storage engines.

INFORMATION_SCHEMA NameSHOW NameRemarks
ENGINEEngineMySQL extension
SUPPORTSupportMySQL extension
COMMENTCommentMySQL extension
TRANSACTIONSTransactionsMySQL extension
XAXAMySQL extension
SAVEPOINTSSavepointsMySQL extension

Notes:

  • The ENGINES table is a nonstandard table.

See also Section 13.7.5.17, “SHOW ENGINES Syntax”.

19.7. The INFORMATION_SCHEMA EVENTS Table

The EVENTS table provides information about scheduled events, which are discussed in Section 18.4, “Using the Event Scheduler”. The SHOW Name values correspond to column names of the SHOW EVENTS statement.

INFORMATION_SCHEMA NameSHOW NameRemarks
EVENT_CATALOG def, MySQL extension
EVENT_SCHEMADbMySQL extension
EVENT_NAMENameMySQL extension
DEFINERDefinerMySQL extension
TIME_ZONETime zoneMySQL extension
EVENT_BODY MySQL extension
EVENT_DEFINITION MySQL extension
EVENT_TYPETypeMySQL extension
EXECUTE_ATExecute atMySQL extension
INTERVAL_VALUEInterval valueMySQL extension
INTERVAL_FIELDInterval fieldMySQL extension
SQL_MODE MySQL extension
STARTSStartsMySQL extension
ENDSEndsMySQL extension
STATUSStatusMySQL extension
ON_COMPLETION MySQL extension
CREATED MySQL extension
LAST_ALTERED MySQL extension
LAST_EXECUTED MySQL extension
EVENT_COMMENT MySQL extension
ORIGINATOROriginatorMySQL extension
CHARACTER_SET_CLIENTcharacter_set_clientMySQL extension
COLLATION_CONNECTIONcollation_connectionMySQL extension
DATABASE_COLLATIONDatabase CollationMySQL extension

Notes:

  • The EVENTS table is a nonstandard table.

  • EVENT_CATALOG: The value of this column is always def.

  • EVENT_SCHEMA: The name of the schema (database) to which this 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; in MySQL 5.6, this is always SQL.

    This column is not to be confused with the column of the same name (now named EVENT_DEFINITION) that existed in earlier MySQL versions.

  • 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 2006-02-09 14:05:30, the value shown in this column would be '2006-02-10 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 recurring events, this column contains the numeric portion of the event's EVERY clause.

    For a one-time event (that is, an event whose timing is determined by an AT clause), this column is NULL.

  • INTERVAL_FIELD: For recurring events, this column contains the units portion of the EVERY clause governing the timing of the event. Thus, this column contains a value such as 'YEAR', 'QUARTER', 'DAY', and so on.

    For a one-time event (that is, an event whose timing is determined by an AT clause), this column is NULL.

  • SQL_MODE: The SQL mode in effect at the time the event was created or altered.

  • STARTS: 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: One of the three values 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 was replicated to the current MySQL server which is acting as a slave, but the event is not presently being executed on the slave. See Section 16.4.1.10, “Replication of Invoked Features”, for more 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 DATETIME value.

  • LAST_ALTERED: The date and time when the event was last modified. This is a DATETIME value. If the event has not been modified since its creation, this column holds the same value as the CREATED column.

  • LAST_EXECUTED: The date and time when the event last executed. 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 a comment, if the event has one. If not, the value of this column is an empty string.

  • 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 is the session value of the character_set_client system variable when the event was created. COLLATION_CONNECTION is the session value of the collation_connection system variable when the event was created. DATABASE_COLLATION is the collation of the database with which the event is associated.

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
    ENABLED;

(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: test
          EVENT_NAME: e_daily
             DEFINER: paul@localhost
           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:
              STARTS: 2008-09-03 12:13:39
                ENDS: NULL
              STATUS: ENABLED
       ON_COMPLETION: NOT PRESERVE
             CREATED: 2008-09-03 12:13:39
        LAST_ALTERED: 2008-09-03 12:13:39
       LAST_EXECUTED: NULL
       EVENT_COMMENT: Saves total number of sessions then clears the
                      table each day
          ORIGINATOR: 1
CHARACTER_SET_CLIENT: latin1
COLLATION_CONNECTION: latin1_swedish_ci
  DATABASE_COLLATION: latin1_swedish_ci

Times in the EVENTS table are displayed using the event time zone or the current session time zone, as described in Section 18.4.4, “Event Metadata”.

See also Section 13.7.5.19, “SHOW EVENTS Syntax”.

19.8. The INFORMATION_SCHEMA FILES Table

The FILES table provides information about the files in which MySQL tablespace data is stored.

INFORMATION_SCHEMA NameSHOW NameRemarks
FILE_ID MySQL extension
FILE_NAME MySQL extension
FILE_TYPE MySQL extension
TABLESPACE_NAME MySQL extension
TABLE_CATALOG MySQL extension
TABLE_SCHEMA MySQL extension
TABLE_NAME MySQL extension
LOGFILE_GROUP_NAME MySQL extension
LOGFILE_GROUP_NUMBER MySQL extension
ENGINE MySQL extension
FULLTEXT_KEYS MySQL extension
DELETED_ROWS MySQL extension
UPDATE_COUNT MySQL extension
FREE_EXTENTS MySQL extension
TOTAL_EXTENTS MySQL extension
EXTENT_SIZE MySQL extension
INITIAL_SIZE MySQL extension
MAXIMUM_SIZE MySQL extension
AUTOEXTEND_SIZE MySQL extension
CREATION_TIME MySQL extension
LAST_UPDATE_TIME MySQL extension
LAST_ACCESS_TIME MySQL extension
RECOVER_TIME MySQL extension
TRANSACTION_COUNTER MySQL extension
VERSION MySQL extension
ROW_FORMAT MySQL extension
TABLE_ROWS MySQL extension
AVG_ROW_LENGTH MySQL extension
DATA_LENGTH MySQL extension
MAX_DATA_LENGTH MySQL extension
INDEX_LENGTH MySQL extension
DATA_FREE MySQL extension
CREATE_TIME MySQL extension
UPDATE_TIME MySQL extension
CHECK_TIME MySQL extension
CHECKSUM MySQL extension
STATUS MySQL extension
EXTRA MySQL extension

Notes:

  • FILE_ID column values are auto-generated.

  • FILE_NAME is the name of a data file created by CREATE TABLESPACE or ALTER TABLESPACE.

  • FILE_TYPE is the tablespace file type.

  • TABLESPACE_NAME is the name of the tablespace with which the file is associated.

  • Currently, the value of the TABLESPACE_CATALOG column is always NULL.

  • TABLE_NAME is the name of the table with which the file is associated, if any.

  • The EXTENT_SIZE is always 0.

  • There are no SHOW statements associated with the FILES table.

19.9. 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”).

INFORMATION_SCHEMA NameSHOW NameRemarks
VARIABLE_NAMEVariable_name 
VARIABLE_VALUEValue 

Notes:

  • The VARIABLE_VALUE column for each of these tables is defined as VARCHAR(20480).

19.10. 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”).

INFORMATION_SCHEMA NameSHOW NameRemarks
VARIABLE_NAMEVariable_name 
VARIABLE_VALUEValue 

Notes:

  • The VARIABLE_VALUE column for each of these tables is defined as VARCHAR(20480).

19.11. The INFORMATION_SCHEMA KEY_COLUMN_USAGE Table

The KEY_COLUMN_USAGE table describes which key columns have constraints.

INFORMATION_SCHEMA NameSHOW NameRemarks
CONSTRAINT_CATALOG def
CONSTRAINT_SCHEMA  
CONSTRAINT_NAME  
TABLE_CATALOG def
TABLE_SCHEMA  
TABLE_NAME  
COLUMN_NAME  
ORDINAL_POSITION  
POSITION_IN_UNIQUE_CONSTRAINT  
REFERENCED_TABLE_SCHEMA  
REFERENCED_TABLE_NAME  
REFERENCED_COLUMN_NAME  

Notes:

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

  • The value of ORDINAL_POSITION is the column's position within the constraint, not the column's position within the table. Column positions are numbered beginning with 1.

  • The value of POSITION_IN_UNIQUE_CONSTRAINT is NULL for unique and primary-key constraints. For foreign-key constraints, it is the ordinal position in key of the table that is being referenced.

    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.

19.12. The INFORMATION_SCHEMA OPTIMIZER_TRACE Table

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

The OPTIMIZER_TRACE table was added in MySQL 5.6.3.

19.13. The INFORMATION_SCHEMA PARAMETERS Table

The PARAMETERS table provides information about stored procedure and function parameters, and about return values for stored functions. Parameter information is similar to the contents of the param_list column in the mysql.proc table.

INFORMATION_SCHEMA Namemysql.proc NameRemarks
SPECIFIC_CATALOG def
SPECIFIC_SCHEMAdbroutine database
SPECIFIC_NAMEnameroutine name
ORDINAL_POSITION 1, 2, 3, ... for parameters, 0 for function RETURNS clause
PARAMETER_MODE IN, OUT, INOUT (NULL for RETURNS)
PARAMETER_NAME parameter name (NULL for RETURNS)
DATA_TYPE same as for COLUMNS table
CHARACTER_MAXIMUM_LENGTH same as for COLUMNS table
CHARACTER_OCTET_LENGTH same as for COLUMNS table
NUMERIC_PRECISION same as for COLUMNS table
NUMERIC_SCALE same as for COLUMNS table
DATETIME_PRECISION same as for COLUMNS table
CHARACTER_SET_NAME same as for COLUMNS table
COLLATION_NAME same as for COLUMNS table
DTD_IDENTIFIER same as for COLUMNS table
ROUTINE_TYPEtypesame as for ROUTINES table

Notes:

  • 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 describes the data type for 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.

    • DATETIME_PRECISION was added in MySQL 5.6.4.

19.14. The INFORMATION_SCHEMA PARTITIONS Table

The PARTITIONS table provides information about table partitions. See Chapter 17, Partitioning, for more information about partitioning tables.

INFORMATION_SCHEMA NameSHOW NameRemarks
TABLE_CATALOG MySQL extension
TABLE_SCHEMA MySQL extension
TABLE_NAME MySQL extension
PARTITION_NAME MySQL extension
SUBPARTITION_NAME MySQL extension
PARTITION_ORDINAL_POSITION MySQL extension
SUBPARTITION_ORDINAL_POSITION MySQL extension
PARTITION_METHOD MySQL extension
SUBPARTITION_METHOD MySQL extension
PARTITION_EXPRESSION MySQL extension
SUBPARTITION_EXPRESSION MySQL extension
PARTITION_DESCRIPTION MySQL extension
TABLE_ROWS MySQL extension
AVG_ROW_LENGTH MySQL extension
DATA_LENGTH MySQL extension
MAX_DATA_LENGTH MySQL extension
INDEX_LENGTH MySQL extension
DATA_FREE MySQL extension
CREATE_TIME MySQL extension
UPDATE_TIME MySQL extension
CHECK_TIME MySQL extension
CHECKSUM MySQL extension
PARTITION_COMMENT MySQL extension
NODEGROUP MySQL extension
TABLESPACE_NAME MySQL extension

Notes:

  • The PARTITIONS table is a nonstandard table.

    Each record in this table corresponds to an individual partition or subpartition of a partitioned table.

  • TABLE_CATALOG: This column is always def.

  • TABLE_SCHEMA: This column contains the name of the database to which the table belongs.

  • TABLE_NAME: This column contains the name of the table containing the partition.

  • PARTITION_NAME: The name of the partition.

  • SUBPARTITION_NAME: If the PARTITIONS table record represents a subpartition, then this column contains the name of subpartition; otherwise it is 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 17.2, “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 17.2.6, “Subpartitioning”.

  • PARTITION_EXPRESSION: This is 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 record 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              |
    +----------------------+
    1 row in set (0.09 sec)
    
  • 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, then 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 comma-separated list of 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.

  • 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.

  • 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.

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

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

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

  • CREATE_TIME: The time of the partition's or subpartition's creation.

  • UPDATE_TIME: The time that the partition or subpartition was last modified.

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

    Note

    Some storage engines do not update this time; for tables using these storage engines, this value is always NULL.

  • CHECKSUM: The checksum value, if any; otherwise, this column is NULL.

  • PARTITION_COMMENT: This column contains the text of any comment made for the partition.

    Prior to MySQL 5.6.6, the display width of this column was 80 characters, and partition comments which exceeded this length were truncated to fit. As of MySQL 5.6.6, the maximum length for a partition comment is defined as 1024 characters, and the display width of the PARTITION_COMMENT column is increased to 1024 characters to match this limit (Bug #11748924, Bug #37728).

    The default value for this column is an empty string.

  • NODEGROUP: This is the nodegroup to which the partition belongs. This is relevant only to MySQL Cluster tables; otherwise the value of this column is always 0.

  • TABLESPACE_NAME: This column contains the name of the tablespace to which the partition belongs. Currently, the value of this column is always DEFAULT.

  • A nonpartitioned table has one record in INFORMATION_SCHEMA.PARTITIONS; 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. (The PARTITION_COMMENT column in this case is blank.)

19.15. The INFORMATION_SCHEMA PLUGINS Table

The PLUGINS table provides information about server plugins.

INFORMATION_SCHEMA NameSHOW NameRemarks
PLUGIN_NAMENameMySQL extension
PLUGIN_VERSION MySQL extension
PLUGIN_STATUSStatusMySQL extension
PLUGIN_TYPETypeMySQL extension
PLUGIN_TYPE_VERSION MySQL extension
PLUGIN_LIBRARYLibraryMySQL extension
PLUGIN_LIBRARY_VERSION MySQL extension
PLUGIN_AUTHOR MySQL extension
PLUGIN_DESCRIPTION MySQL extension
PLUGIN_LICENSE MySQL extension
LOAD_OPTION MySQL extension

Notes:

  • The PLUGINS table is a nonstandard table.

  • PLUGIN_NAME is the name used to refer to the plugin in statements such as INSTALL PLUGIN and UNINSTALL PLUGIN.

  • PLUGIN_VERSION is the version from the plugin's general type descriptor.

  • PLUGIN_STATUS indicates the plugin status, one of ACTIVE, INACTIVE, DISABLED, or DELETED.

  • PLUGIN_TYPE indicates the type of plugin, such as STORAGE ENGINE, INFORMATION_SCHEMA, or AUTHENTICATION.

  • PLUGIN_TYPE_VERSION is the version from the plugin's type-specific descriptor.

  • PLUGIN_LIBRARY is the name of the plugin shared object 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 indicates the plugin API interface version.

  • PLUGIN_AUTHOR names the plugin author.

  • PLUGIN_DESCRIPTION provides a short description of the plugin.

  • PLUGIN_LICENSE indicates how the plugin is licensed; for example, GPL.

  • LOAD_OPTION indicates how the plugin was loaded. The value is OFF, ON, FORCE, or FORCE_PLUS_PERMANENT. See Section 5.1.8.1, “Installing and Uninstalling Plugins”.

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

These statements are equivalent:

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

SHOW PLUGINS;

For information about plugin data structures that form the basis of the information in the PLUGINS table, see Section 22.2, “The MySQL Plugin API”.

Plugin information is also available using the SHOW PLUGINS statement. See Section 13.7.5.26, “SHOW PLUGINS Syntax”.

19.16. The INFORMATION_SCHEMA PROCESSLIST Table

The PROCESSLIST table provides information about which threads are running.

INFORMATION_SCHEMA NameSHOW NameRemarks
IDIdMySQL extension
USERUserMySQL extension
HOSTHostMySQL extension
DBdbMySQL extension
COMMANDCommandMySQL extension
TIMETimeMySQL extension
STATEStateMySQL extension
INFOInfoMySQL extension

For an extensive description of the table columns, see Section 13.7.5.30, “SHOW PROCESSLIST Syntax”.

Notes:

  • The PROCESSLIST table is a nonstandard table.

  • Like the output from the corresponding SHOW statement, the PROCESSLIST table will only show information 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 INFORMATION_SCHEMA.PROCESSLIST, then MySQL will populate 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, though.

  • Process information is also available from the performance_schema.threads table. However, access to threads does not require a mutex and has minimal impact on server performance. INFORMATION_SCHEMA.PROCESSLIST and SHOW PROCESSLIST have negative performance consequences because they require a mutex. threads also shows information about background threads, which INFORMATION_SCHEMA.PROCESSLIST 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

19.17. The INFORMATION_SCHEMA PROFILING Table

The PROFILING table provides statement profiling information. Its contents correspond to the information produced by the SHOW PROFILES and SHOW PROFILE statements (see Section 13.7.5.32, “SHOW PROFILES Syntax”). The table is empty unless the profiling session variable is set to 1.

INFORMATION_SCHEMA NameSHOW NameRemarks
QUERY_IDQuery_ID 
SEQ 
STATEStatus 
DURATIONDuration 
CPU_USERCPU_user 
CPU_SYSTEMCPU_system 
CONTEXT_VOLUNTARYContext_voluntary 
CONTEXT_INVOLUNTARYContext_involuntary 
BLOCK_OPS_INBlock_ops_in 
BLOCK_OPS_OUTBlock_ops_out 
MESSAGES_SENTMessages_sent 
MESSAGES_RECEIVEDMessages_received 
PAGE_FAULTS_MAJORPage_faults_major 
PAGE_FAULTS_MINORPage_faults_minor 
SWAPSSwaps 
SOURCE_FUNCTIONSource_function 
SOURCE_FILESource_file 
SOURCE_LINESource_line 

Notes:

  • QUERY_ID is a numeric statement identifier.

  • SEQ is a sequence number indicating the display order for rows with the same QUERY_ID value.

  • STATE is the profiling state to which the row measurements apply.

  • DURATION indicates how long statement execution remained in the given state, in seconds.

  • CPU_USER and CPU_SYSTEM indicate user and system CPU use, in seconds.

  • CONTEXT_VOLUNTARY and CONTEXT_INVOLUNTARY indicate how many voluntary and involuntary context switches occurred.

  • BLOCK_OPS_IN and BLOCK_OPS_OUT indicate the number of block input and output operations.

  • MESSAGES_SENT and MESSAGES_RECEIVED indicate the number of communication messages sent and received.

  • PAGE_FAULTS_MAJOR and PAGE_FAULTS_MINOR indicate the number of major and minor page faults.

  • SWAPS indicates how many swaps occurred.

  • SOURCE_FUNCTION, SOURCE_FILE, and SOURCE_LINE provide information indicating where in the source code the profiled state executes.

19.18. The INFORMATION_SCHEMA REFERENTIAL_CONSTRAINTS Table

The REFERENTIAL_CONSTRAINTS table provides information about foreign keys.

INFORMATION_SCHEMA NameSHOW NameRemarks
CONSTRAINT_CATALOG def
CONSTRAINT_SCHEMA  
CONSTRAINT_NAME  
UNIQUE_CONSTRAINT_CATALOG def
UNIQUE_CONSTRAINT_SCHEMA  
UNIQUE_CONSTRAINT_NAME  
MATCH_OPTION  
UPDATE_RULE  
DELETE_RULE  
TABLE_NAME  
REFERENCED_TABLE_NAME  

Notes:

  • TABLE_NAME has the same value as TABLE_NAME in INFORMATION_SCHEMA.TABLE_CONSTRAINTS.

  • CONSTRAINT_SCHEMA and CONSTRAINT_NAME identify the foreign key.

  • UNIQUE_CONSTRAINT_SCHEMA, UNIQUE_CONSTRAINT_NAME, and REFERENCED_TABLE_NAME identify the referenced key.

  • The only valid value at this time for MATCH_OPTION is NONE.

  • The possible values for UPDATE_RULE or DELETE_RULE are CASCADE, SET NULL, SET DEFAULT, RESTRICT, NO ACTION.

19.19. The INFORMATION_SCHEMA ROUTINES Table

The ROUTINES table provides information about stored routines (both procedures and functions). The ROUTINES table does not include 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.

INFORMATION_SCHEMA Namemysql.proc NameRemarks
SPECIFIC_NAMEspecific_name 
ROUTINE_CATALOG def
ROUTINE_SCHEMAdb 
ROUTINE_NAMEname 
ROUTINE_TYPEtype{PROCEDURE|FUNCTION}
DATA_TYPE same as for COLUMNS table
CHARACTER_MAXIMUM_LENGTH same as for COLUMNS table
CHARACTER_OCTET_LENGTH same as for COLUMNS table
NUMERIC_PRECISION same as for COLUMNS table
NUMERIC_SCALE same as for COLUMNS table
DATETIME_PRECISION same as for COLUMNS table
CHARACTER_SET_NAME same as for COLUMNS table
COLLATION_NAME same as for COLUMNS table
DTD_IDENTIFIER data type descriptor
ROUTINE_BODY SQL
ROUTINE_DEFINITIONbody_utf8 
EXTERNAL_NAME NULL
EXTERNAL_LANGUAGElanguageNULL
PARAMETER_STYLE SQL
IS_DETERMINISTICis_deterministic 
SQL_DATA_ACCESSsql_data_access 
SQL_PATH NULL
SECURITY_TYPEsecurity_type 
CREATEDcreated 
LAST_ALTEREDmodified 
SQL_MODEsql_modeMySQL extension
ROUTINE_COMMENTcommentMySQL extension
DEFINERdefinerMySQL extension
CHARACTER_SET_CLIENT MySQL extension
COLLATION_CONNECTION MySQL extension
DATABASE_COLLATION MySQL extension

Notes:

  • 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.

  • CHARACTER_SET_CLIENT is the session value of the character_set_client system variable when the routine was created. COLLATION_CONNECTION is the session value of the collation_connection system variable when the routine was created. DATABASE_COLLATION is the collation of the database with which the routine is associated.

  • The DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, CHARACTER_OCTET_LENGTH, NUMERIC_PRECISION, NUMERIC_SCALE, DATETIME_PRECISION, CHARACTER_SET_NAME, and COLLATION_NAME columns provide information about the data type for the RETURNS clause of stored functions. If a stored routine is a stored procedure, these columns all are NULL. DATETIME_PRECISION was added in MySQL 5.6.4.

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

19.20. The INFORMATION_SCHEMA SCHEMATA Table

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

INFORMATION_SCHEMA NameSHOW NameRemarks
CATALOG_NAME def
SCHEMA_NAME Database
DEFAULT_CHARACTER_SET_NAME  
DEFAULT_COLLATION_NAME  
SQL_PATH NULL

The following statements are equivalent:

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

SHOW DATABASES
  [LIKE 'wild']

19.21. The INFORMATION_SCHEMA SCHEMA_PRIVILEGES Table

The SCHEMA_PRIVILEGES table provides information about schema (database) privileges. This information comes from the mysql.db grant table.

INFORMATION_SCHEMA NameSHOW NameRemarks
GRANTEE 'user_name'@'host_name' value, MySQL extension
TABLE_CATALOG def, MySQL extension
TABLE_SCHEMA MySQL extension
PRIVILEGE_TYPE MySQL extension
IS_GRANTABLE MySQL extension

Notes:

  • This is a nonstandard table. It takes its values from the mysql.db table.

19.22. The INFORMATION_SCHEMA STATISTICS Table

The STATISTICS table provides information about table indexes.

INFORMATION_SCHEMA NameSHOW NameRemarks
TABLE_CATALOG def
TABLE_SCHEMA = Database
TABLE_NAMETable 
NON_UNIQUENon_unique 
INDEX_SCHEMA = Database
INDEX_NAMEKey_name 
SEQ_IN_INDEXSeq_in_index 
COLUMN_NAMEColumn_name 
COLLATIONCollation 
CARDINALITYCardinality 
SUB_PARTSub_partMySQL extension
PACKEDPackedMySQL extension
NULLABLENullMySQL extension
INDEX_TYPEIndex_typeMySQL extension
COMMENTCommentMySQL extension

Notes:

  • There is no standard table for indexes. The preceding list is similar to what SQL Server 2000 returns for sp_statistics, except that we replaced the name QUALIFIER with CATALOG and we replaced the name OWNER with SCHEMA.

    Clearly, the preceding table and the output from SHOW INDEX are derived from the same parent. So the correlation is already close.

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

19.23. The INFORMATION_SCHEMA TABLES Table

The TABLES table provides information about tables in databases.

INFORMATION_SCHEMA NameSHOW NameRemarks
TABLE_CATALOG def
TABLE_SCHEMATable_... 
TABLE_NAMETable_... 
TABLE_TYPE  
ENGINEEngineMySQL extension
VERSIONVersionThe version number of the table's .frm file, MySQL extension
ROW_FORMATRow_formatMySQL extension
TABLE_ROWSRowsMySQL extension
AVG_ROW_LENGTHAvg_row_lengthMySQL extension
DATA_LENGTHData_lengthMySQL extension
MAX_DATA_LENGTHMax_data_lengthMySQL extension
INDEX_LENGTHIndex_lengthMySQL extension
DATA_FREEData_freeMySQL extension
AUTO_INCREMENTAuto_incrementMySQL extension
CREATE_TIMECreate_timeMySQL extension
UPDATE_TIMEUpdate_timeMySQL extension
CHECK_TIMECheck_timeMySQL extension
TABLE_COLLATIONCollationMySQL extension
CHECKSUMChecksumMySQL extension
CREATE_OPTIONSCreate_optionsMySQL extension
TABLE_COMMENTCommentMySQL extension

Notes:

  • TABLE_SCHEMA and TABLE_NAME are a single field in a SHOW display, for example Table_in_db1.

  • TABLE_TYPE should be BASE TABLE or VIEW. Currently, the TABLES table does not list TEMPORARY tables.

  • For partitioned tables, the ENGINE column shows the name of the storage engine used by all partitions. (Previously, this column showed PARTITION for such tables.)

  • The TABLE_ROWS column is NULL if the table is in the INFORMATION_SCHEMA database.

    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.)

  • The DATA_FREE column shows the free space in bytes for InnoDB tables.

  • We have nothing for the table's default character set. TABLE_COLLATION is close, because collation names begin with a character set name.

  • The CREATE_OPTIONS column shows partitioned if the table is partitioned.

The following statements are equivalent:

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

SHOW TABLES
  FROM db_name
  [LIKE 'wild']

19.24. The INFORMATION_SCHEMA TABLESPACES Table

The TABLESPACES table provides information about active tablespaces.

INFORMATION_SCHEMA NameSHOW NameRemarks
TABLESPACE_NAME MySQL extension
ENGINE MySQL extension
TABLESPACE_TYPE MySQL extension
LOGFILE_GROUP_NAME MySQL extension
EXTENT_SIZE MySQL extension
AUTOEXTEND_SIZE MySQL extension
MAXIMUM_SIZE MySQL extension
NODEGROUP_ID MySQL extension
TABLESPACE_COMMENT MySQL extension

19.25. The INFORMATION_SCHEMA TABLE_CONSTRAINTS Table

The TABLE_CONSTRAINTS table describes which tables have constraints.

INFORMATION_SCHEMA NameSHOW NameRemarks
CONSTRAINT_CATALOG def
CONSTRAINT_SCHEMA  
CONSTRAINT_NAME  
TABLE_SCHEMA  
TABLE_NAME  
CONSTRAINT_TYPE  

Notes:

  • The CONSTRAINT_TYPE value can be UNIQUE, PRIMARY KEY, or FOREIGN KEY.

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

  • The CONSTRAINT_TYPE column can contain one of these values: UNIQUE, PRIMARY KEY, FOREIGN KEY, CHECK. This is a CHAR (not ENUM) column. The CHECK value is not available until we support CHECK.

19.26. The INFORMATION_SCHEMA TABLE_PRIVILEGES Table

The TABLE_PRIVILEGES table provides information about table privileges. This information comes from the mysql.tables_priv grant table.

INFORMATION_SCHEMA NameSHOW NameRemarks
GRANTEE 'user_name'@'host_name' value
TABLE_CATALOG def
TABLE_SCHEMA  
TABLE_NAME  
PRIVILEGE_TYPE  
IS_GRANTABLE  

Notes:

The following statements are not equivalent:

SELECT ... FROM INFORMATION_SCHEMA.TABLE_PRIVILEGES

SHOW GRANTS ...

19.27. The INFORMATION_SCHEMA TRIGGERS Table

The TRIGGERS table provides information about triggers. You can see results only for databases and tables for which you have the TRIGGER privilege.

INFORMATION_SCHEMA NameSHOW NameRemarks
TRIGGER_CATALOG def
TRIGGER_SCHEMA  
TRIGGER_NAMETrigger 
EVENT_MANIPULATIONEvent 
EVENT_OBJECT_CATALOG def
EVENT_OBJECT_SCHEMA  
EVENT_OBJECT_TABLETable 
ACTION_ORDER 0
ACTION_CONDITION NULL
ACTION_STATEMENTStatement 
ACTION_ORIENTATION ROW
ACTION_TIMINGTiming 
ACTION_REFERENCE_OLD_TABLE NULL
ACTION_REFERENCE_NEW_TABLE NULL
ACTION_REFERENCE_OLD_ROW OLD
ACTION_REFERENCE_NEW_ROW NEW
CREATED NULL (0)
SQL_MODE MySQL extension
DEFINER MySQL extension
CHARACTER_SET_CLIENT MySQL extension
COLLATION_CONNECTION MySQL extension
DATABASE_COLLATION MySQL extension

Notes:

  • The TRIGGER_SCHEMA and TRIGGER_NAME columns contain the name of the database in which the trigger occurs and the trigger name, respectively.

  • The EVENT_MANIPULATION column contains one of the values 'INSERT', 'DELETE', or 'UPDATE'.

  • As noted in Section 18.3, “Using Triggers”, every trigger is associated with exactly one table. The EVENT_OBJECT_SCHEMA and EVENT_OBJECT_TABLE columns contain the database in which this table occurs, and the table's name.

  • The ACTION_ORDER column contains the ordinal position of the trigger's action within the list of all similar triggers on the same table. Currently, 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.

  • The ACTION_STATEMENT column contains the statement to be executed when the trigger is invoked. This is the same as the text displayed in the Statement column of the output from SHOW TRIGGERS. Note that this text uses UTF-8 encoding.

  • The ACTION_ORIENTATION column always contains the value 'ROW'.

  • The ACTION_TIMING column contains one of the two values 'BEFORE' or 'AFTER'.

  • The columns ACTION_REFERENCE_OLD_ROW and ACTION_REFERENCE_NEW_ROW contain the old and new column identifiers, respectively. This means that ACTION_REFERENCE_OLD_ROW always contains the value 'OLD' and ACTION_REFERENCE_NEW_ROW always contains the value 'NEW'.

  • The SQL_MODE column shows the server SQL mode that was in effect at the time when the trigger was created (and thus which remains in effect for this trigger whenever it is invoked, regardless of the current server SQL mode). The possible range of values for this column is the same as that of the sql_mode system variable. See Section 5.1.7, “Server SQL Modes”.

  • The DEFINER column indicates who defined the trigger.

  • CHARACTER_SET_CLIENT is the session value of the character_set_client system variable when the trigger was created. COLLATION_CONNECTION is the session value of the collation_connection system variable when the trigger was created. DATABASE_COLLATION is the collation of the database with which the trigger is associated.

  • The following columns currently always contain NULL: ACTION_CONDITION, ACTION_REFERENCE_OLD_TABLE, ACTION_REFERENCE_NEW_TABLE, and CREATED.

Example, using the ins_sum trigger defined in Section 18.3, “Using Triggers”:

mysql> SELECT * FROM INFORMATION_SCHEMA.TRIGGERS\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:
                   DEFINER: me@localhost

See also Section 13.7.5.39, “SHOW TRIGGERS Syntax”.

19.28. The INFORMATION_SCHEMA USER_PRIVILEGES Table

The USER_PRIVILEGES table provides information about global privileges. This information comes from the mysql.user grant table.

INFORMATION_SCHEMA NameSHOW NameRemarks
GRANTEE 'user_name'@'host_name' value, MySQL extension
TABLE_CATALOG def, MySQL extension
PRIVILEGE_TYPE MySQL extension
IS_GRANTABLE MySQL extension

Notes:

  • This is a nonstandard table. It takes its values from the mysql.user table.

19.29. 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.

INFORMATION_SCHEMA NameSHOW NameRemarks
TABLE_CATALOG def
TABLE_SCHEMA  
TABLE_NAME  
VIEW_DEFINITION  
CHECK_OPTION  
IS_UPDATABLE  
DEFINER  
SECURITY_TYPE  
CHARACTER_SET_CLIENT MySQL extension
COLLATION_CONNECTION MySQL extension

Notes:

  • The VIEW_DEFINITION column has most of what you see in the Create Table field 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
  • The CHECK_OPTION column has a value of NONE, CASCADE, or LOCAL.

  • 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 the view is not updatable, statements such UPDATE, DELETE, and INSERT are illegal and will be rejected. (Note that even if a view is updatable, it might not be possible to insert into it; for details, refer to Section 13.1.16, “CREATE VIEW Syntax”.)

  • The DEFINER column indicates who defined the view. SECURITY_TYPE has a value of DEFINER or INVOKER.

  • CHARACTER_SET_CLIENT is the session value of the character_set_client system variable when the view was created. COLLATION_CONNECTION is the session value of the collation_connection system variable when the view was created.

MySQL lets you use 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 will 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.

19.30. INFORMATION_SCHEMA Tables for InnoDB

The InnoDB tables related to the InnoDB storage engine serve two purposes:

  • You can monitor ongoing InnoDB activity, to detect inefficiencies before they turn into issues, or to troubleshoot performance and capacity issues that do occur. 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. The monitoring information deals with:

    • InnoDB table compression, a feature whose use depends on a balance between I/O reduction, CPU usage, buffer pool management, and how much compression is possible for your data.

    • Transactions and locks, features that balance high performance for a single operation, against the ability to run multiple operations concurrently. (Transactions are the high-level, user-visible aspect of concurrency. Locks are the low-level mechanism that transactions use to avoid reading or writing unreliable data.)

  • You can extract information about schema objects managed by InnoDB, using the INNODB_SYS_* tables. This information comes from the InnoDB data dictionary, which cannot be queried directly like regular InnoDB tables. Traditionally, you would get this type of information using the techniques from Section 14.2.4.4, “SHOW ENGINE INNODB STATUS and the InnoDB Monitors”, setting up InnoDB monitors and parsing the output from the SHOW ENGINE INNODB STATUS command. The InnoDB interface offers a simpler, familiar technique to access this data.

19.30.1. The INFORMATION_SCHEMA INNODB_CMP and INNODB_CMP_RESET Tables

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

Table 19.1. Columns of INNODB_CMP and INNODB_CMP_RESET

Column nameDescription
PAGE_SIZECompressed page size in bytes.
COMPRESS_OPSNumber of times a B-tree page of the 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_OKNumber of times a B-tree page of the size PAGE_SIZE has been successfully compressed. This count should never exceed COMPRESS_OPS.
COMPRESS_TIMETotal time in seconds spent in attempts to compress B-tree pages of the size PAGE_SIZE.
UNCOMPRESS_OPSNumber of times a B-tree page of the 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_TIMETotal time in seconds spent in uncompressing B-tree pages of the size PAGE_SIZE.

Notes:

19.30.2. 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 contain 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.

Table 19.2. Columns of INNODB_CMP_PER_INDEX and INNODB_CMP_PER_INDEX_RESET

Column nameDescription
  
DATABASE_NAMEDatabase containing the applicable table.
TABLE_NAMETable to monitor for compression statistics.
INDEX_NAMEIndex to monitor for compression statistics.
COMPRESS_OPSNumber 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_OKNumber 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_TIMETotal amount of CPU time, in seconds, used for compressing data in this index.
UNCOMPRESS_OPSNumber 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_TIMETotal amount of CPU time, in seconds, used for uncompressing data in this index.

Notes:

19.30.3. The INFORMATION_SCHEMA INNODB_CMPMEM and INNODB_CMPMEM_RESET Tables

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

Table 19.3. Columns of INNODB_CMPMEM and INNODB_CMPMEM_RESET

Column nameDescription
PAGE_SIZEBlock size in bytes. Each record of this table describes blocks of this size.
PAGES_USEDNumber of blocks of the size PAGE_SIZE that are currently in use.
PAGES_FREENumber of blocks of the 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_OPSNumber of times a block of the 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 table INNODB_CMPMEM_RESET resets this count.
RELOCATION_TIMETotal time in microseconds spent in relocating blocks of the size PAGE_SIZE. Reading from the table INNODB_CMPMEM_RESET resets this count.

Notes:

19.30.4. The INFORMATION_SCHEMA INNODB_TRX Table

The INNODB_TRX table contains information about every transaction 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.

Table 19.4. INNODB_TRX Columns

Column nameDescription
TRX_IDUnique transaction ID number, internal to InnoDB. (Starting in MySQL 5.6, these IDs are not created for transactions that are read-only and non-locking. See Section 14.2.4.2.3, “Optimizations for Read-Only Transactions” for details.)
TRX_WEIGHTThe 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 rollback. Transactions that have changed non-transactional tables are considered heavier than others, regardless of the number of altered and locked rows.
TRX_STATETransaction execution state. One of RUNNING, LOCK WAIT, ROLLING BACK or COMMITTING.
TRX_STARTEDTransaction start time.
TRX_REQUESTED_LOCK_IDID of the lock the transaction is currently waiting for (if TRX_STATE is LOCK WAIT, otherwise NULL). Details about the lock can be found by joining with INNODB_LOCKS on LOCK_ID.
TRX_WAIT_STARTEDTime when the transaction started waiting on the lock (if TRX_STATE is LOCK WAIT, otherwise NULL).
TRX_MYSQL_THREAD_IDMySQL thread ID. Can be used for joining with PROCESSLIST on ID. See Section 14.2.4.3.4.3, “Possible Inconsistency with PROCESSLIST.
TRX_QUERYThe SQL query that is being executed by the transaction.
TRX_OPERATION_STATEThe transaction's current operation, or NULL.
TRX_TABLES_IN_USEThe number of InnoDB tables used while processing the current SQL statement of this transaction.
TRX_TABLES_LOCKEDNumber of InnoDB tables that currently have any locks. (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_STRUCTSThe number of locks reserved by the transaction.
TRX_LOCK_MEMORY_BYTESTotal size taken up by the lock structures of this transaction in memory.
TRX_ROWS_LOCKEDApproximate 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_MODIFIEDThe number of modified and inserted rows in this transaction.
TRX_CONCURRENCY_TICKETSA value indicating how much work the current transaction can do before being swapped out, as specified by the innodb_concurrency_tickets option.
TRX_ISOLATION_LEVELThe isolation level of the current transaction.
TRX_UNIQUE_CHECKSWhether unique checks are turned on or off for the current transaction. (They might be turned off during a bulk data load, for example.)
TRX_FOREIGN_KEY_CHECKSWhether foreign key checks are turned on or off for the current transaction. (They might be turned off during a bulk data load, for example.)
TRX_LAST_FOREIGN_KEY_ERRORDetailed error message for last FK error, or NULL.
TRX_ADAPTIVE_HASH_LATCHEDWhether or not 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_TIMEOUTWhether to relinquish the search latch immediately for the adaptive hash index, or reserve it across calls from MySQL. When there is no AHI 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. (5.6.4 and up.)

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 the autocommit setting turned on so that the transaction will only contain this one statement. (5.6.4 and up.) 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.


Notes:

19.30.5. The INFORMATION_SCHEMA INNODB_LOCKS Table

The INNODB_LOCKS table contains 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.

Table 19.5. INNODB_LOCKS Columns

Column nameDescription
LOCK_IDUnique 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 not guaranteed to remain the same in future releases. Do not write programs that parse the LOCK_ID value.
LOCK_TRX_IDID of the transaction holding this lock. Details about the transaction can be found by joining with INNODB_TRX on TRX_ID.
LOCK_MODEMode of the lock. One of S, X, IS, IX, S_GAP, X_GAP, IS_GAP, IX_GAP, or AUTO_INC for shared, exclusive, intention shared, intention exclusive row locks, shared and exclusive gap locks, intention shared and intention exclusive gap locks, and auto-increment table level lock, respectively. Refer to the sections Section 14.2.3.2, “InnoDB Lock Modes” and Section 14.2.3.1, “The InnoDB Transaction Model and Locking” for information on InnoDB locking.
LOCK_TYPEType of the lock. One of RECORD or TABLE for record (row) level or table level locks, respectively.
LOCK_TABLEName of the table that has been locked or contains locked records.
LOCK_INDEXName of the index if LOCK_TYPE='RECORD', otherwise NULL.
LOCK_SPACETablespace ID of the locked record if LOCK_TYPE='RECORD', otherwise NULL.
LOCK_PAGEPage number of the locked record if LOCK_TYPE='RECORD', otherwise NULL.
LOCK_RECHeap number of the locked record within the page if LOCK_TYPE='RECORD', otherwise NULL.
LOCK_DATAPrimary key of the locked record if LOCK_TYPE='RECORD', otherwise NULL. This column contains the value(s) of the primary key column(s) in the locked row, formatted as a valid SQL string (ready to be copied to SQL commands). If there is no primary key then the InnoDB internal unique row ID number is used. 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.

Notes:

19.30.6. 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.

Table 19.6. INNODB_LOCK_WAITS Columns

Column nameDescription
REQUESTING_TRX_IDID of the requesting transaction.
REQUESTED_LOCK_IDID of the lock for which a transaction is waiting. Details about the lock can be found by joining with INNODB_LOCKS on LOCK_ID.
BLOCKING_TRX_IDID of the blocking transaction.
BLOCKING_LOCK_IDID of a lock held by a transaction blocking another transaction from proceeding. Details about the lock can be found by joining with INNODB_LOCKS on LOCK_ID.

Notes:

19.30.7. The INFORMATION_SCHEMA INNODB_SYS_TABLES Table

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

Table 19.7. INNODB_SYS_TABLES Columns

Column nameDescription
TABLE_IDAn identifier for each InnoDB table that is unique across all databases in the instance.
NAMEThe name of the table. Preceded by the database name where appropriate, for example test/t1. InnoDB system table names are in all uppercase. 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.
FLAG0 = InnoDB system table, 1 = user table.
N_COLSThe number of columns in the table.
SPACEAn 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.

Notes:

  • Since the INFORMATION_SCHEMA is a general-purpose way to monitor the MySQL server, use this table rather than the corresponding InnoDB system table for any new monitoring application you develop.

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

19.30.8. The INFORMATION_SCHEMA INNODB_SYS_INDEXES Table

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

Table 19.8. INNODB_SYS_INDEXES Columns

Column nameDescription
INDEX_IDAn identifier for each index that is unique across all the databases in an instance.
NAMEThe name of the index. User-created indexes have names in all lowercase. Indexes created implicitly by InnoDB have names in all lowercase. The index names are not necessarily unique. Indexes created implicitly by InnoDB have consistent names: PRIMARY for a primary key index, GEN_CLUST_INDEX for the index representing a primary key when one is not specified, ID_IND, FOR_IND for validating a foreign key constraint, and REF_IND.
TABLE_IDAn identifier representing the table associated with the index; the same value from INNODB_SYS_TABLES.TABLE_ID.
TYPEA numeric identifier signifying the kind of index, in the range 0..3.
N_FIELDSThe number of columns in the index key. For the 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
SPACEAn identifier for the tablespace where the index 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. Because all indexes for a table reside in the same tablespace as the table, this value is not necessarily unique.

Notes:

  • Since the INFORMATION_SCHEMA is a general-purpose way to monitor the MySQL server, use this table rather than the corresponding InnoDB system table for any new monitoring application you develop.

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

19.30.9. The INFORMATION_SCHEMA INNODB_SYS_COLUMNS Table

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

Table 19.9. INNODB_SYS_COLUMNS Columns

Column nameDescription
TABLE_IDAn identifier representing the table associated with the column; the same value from INNODB_SYS_TABLES.TABLE_ID.
NAMEThe name of each column in each table. These names can be uppercase or lowercase depending on the lower_case_table_names setting. There are no special system-reserved names for columns.
POSThe 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.
MTYPEA 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.
PRTYPEThe InnoDB precise type, a binary value with bits representing MySQL data type, character set code, and nullability.
LENThe column length, for example 4 for INT and 8 for BIGINT. For character columns in multi-byte 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.

Notes:

  • Since the INFORMATION_SCHEMA is a general-purpose way to monitor the MySQL server, use this table rather than the corresponding InnoDB system table for any new monitoring application you develop.

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

19.30.10. The INFORMATION_SCHEMA INNODB_SYS_FIELDS Table

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

Table 19.10. INNODB_SYS_FIELDS Columns

Column nameDescription
INDEX_IDAn identifier for the index associated with this key field, using the same value as in INNODB_SYS_INDEXES.INDEX_ID.
NAMEThe name of the original column from the table, using the same value as in INNODB_SYS_COLUMNS.NAME.
POSThe 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.

Notes:

  • Since the INFORMATION_SCHEMA is a general-purpose way to monitor the MySQL server, use this table rather than the corresponding InnoDB system table for any new monitoring application you develop.

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

19.30.11. The INFORMATION_SCHEMA INNODB_SYS_FOREIGN Table

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

Table 19.11. INNODB_SYS_FOREIGN Columns

Column nameDescription
IDThe name (not a numeric value) of the foreign key index. Preceded by the database name, for example, test/products_fk.
FOR_NAMEThe name of the child table in this foreign key relationship.
REF_NAMEThe name of the parent table in this foreign key relationship.
N_COLSThe number of columns in the foreign key index.
TYPEA collection of bit flags with information about the foreign key column, ORed together. 1 = ON DELETE CASCADE, 2 = ON UPDATE SET NULL, 4 = ON UPDATE CASCADE, 8 = ON UPDATE SET NULL, 16 = ON DELETE NO ACTION, 32 = ON UPDATE NO ACTION.

Notes:

  • Since the INFORMATION_SCHEMA is a general-purpose way to monitor the MySQL server, use this table rather than the corresponding InnoDB system table for any new monitoring application you develop.

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

19.30.12. 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.

Table 19.12. INNODB_SYS_FOREIGN_COLS Columns

Column nameDescription
IDThe foreign key index associated with this index key field, using the same value as INNODB_SYS_FOREIGN.ID.
FOR_COL_NAMEThe name of the associated column in the child table.
REF_COL_NAMEThe name of the associated column in the parent table.
POSThe ordinal position of this key field within the foreign key index, starting from 0.

Notes:

  • Since the INFORMATION_SCHEMA is a general-purpose way to monitor the MySQL server, use this table rather than the corresponding InnoDB system table for any new monitoring application you develop.

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

19.30.13. The INFORMATION_SCHEMA INNODB_SYS_TABLESTATS View

The INNODB_SYS_TABLESTATS view provides status information about performance statistics for InnoDB tables. These statistics represent low-level information 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 corresponding to data stored on disk.

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

Table 19.13. INNODB_SYS_TABLESTATS Columns

Column nameDescription
TABLE_IDAn identifier representing the table for which statistics are available, using the same value as INNODB_SYS_TABLES.TABLE_ID.
NAMEThe name of the table, using the same value as INNODB_SYS_TABLES.NAME.
STATS_INITIALIZEDThe value is Initialized if the statistics are already collected, Uninitialized if not.
NUM_ROWSThe current estimated number of rows in the table. Updated after each DML operation. Could be imprecise if uncommitted transactions are inserting into or deleting from the table.
CLUST_INDEX_SIZENumber 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_SIZENumber 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_COUNTERThe number of rows modified by DML operations, such as INSERT, UPDATE, DELETE, and also cascade operations from foreign keys.
AUTOINC
REF_COUNTWhen this counter reaches zero, the table metadata can be evicted from the table cache.

Notes:

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

  • Since the INFORMATION_SCHEMA is a general-purpose way to monitor the MySQL server, use this table rather than the corresponding InnoDB system table for any new monitoring application you develop.

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

19.30.14. The INFORMATION_SCHEMA INNODB_BUFFER_PAGE Table

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

Table 19.14. INNODB_BUFFER_PAGE Columns

Column nameDescription
POOL_IDBuffer Pool ID. An identifier to distinguish between multiple buffer pool instances.
BLOCK_IDBuffer Pool Block ID.
SPACETablespace ID. Uses the same value as in INNODB_SYS_TABLES.SPACE.
PAGE_NUMBERPage number.
PAGE_TYPEPage type string. One of allocated (Freshly allocated page), index (B-tree node), undo_log (Undo log page), inode (Index node), ibuf_free_list (Insert buffer free list), ibuf_bitmap (Insert buffer bitmap), system (System page), trx_system (Transaction system data), file_space_header (File space header), extent_descriptor (Extent descriptor page), blob (Uncompressed BLOB page), compressed_blob (First compressed BLOB page), compressed_blob2 (Subsequent comp BLOB page), unknown (unknown).
FLUSH_TYPEFlush type.
FIX_COUNTNumber of threads using this block within the buffer pool. When zero, the block is eligible to be evicted.
IS_HASHEDWhether hash index has been built on this page.
NEWEST_MODIFICATIONLog Sequence Number of the youngest modification.
OLDEST_MODIFICATIONLog Sequence Number of the oldest modification.
ACCESS_TIMETime of first access.
TABLE_NAMEName of the table the page belongs to.
INDEX_NAMEName of the index the page belongs to. It can be the name of a clustered index or a secondary index.
NUMBER_RECORDSNumber of records within the page.
DATA_SIZESum of the sizes of the records.
COMPRESSED_SIZECompressed page size. Null for pages that are not compressed.
PAGE_STATEPage state. A page with valid data has one of the following states: FILE_PAGE (buffers a page of data from a file), MEMORY (buffers a page from an in-memory object), Other possible states (managed by InnoDB) are: null, READY_FOR_USE, NOT_USED, REMOVE_HASH.
IO_FIXSpecifies whether any I/O is pending for this page: IO_NONE = no pending I/O, IO_READ = read pending, IO_WRITE = write pending.
IS_OLDbpage->old.
FREE_PAGE_CLOCKbpage->freed_page_clock.

Notes:

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

  • Since the INFORMATION_SCHEMA is a general-purpose way to monitor the MySQL server, use this table rather than the corresponding InnoDB system table for any new monitoring application you develop.

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

19.30.15. The INFORMATION_SCHEMA INNODB_BUFFER_PAGE_LRU Table

The INNODB_BUFFER_PAGE_LRU table holds 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 definition for this page is the same as for INNODB_BUFFER_PAGE, except this table has an LRU_POSITION column instead of BLOCK_ID.

Notes:

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

    Since the INFORMATION_SCHEMA is a general-purpose way to monitor the MySQL server, use this table rather than the corresponding InnoDB system table for any new monitoring application you develop.

  • Querying this table can require MySQL to allocate a large block of contiguous memory, more than 64 bytes time 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.

19.30.16. The INFORMATION_SCHEMA INNODB_BUFFER_POOL_STATS Table

The INNODB_BUFFER_POOL_STATS table represents the same kinds of InnoDB buffer pool information as the output from SHOW ENGINE INNODB STATUS.

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.

Column meanings in this table are intended to be self-explanatory for developers who formerly parsed the SHOW ENGINE INNODB STATUS to get these values.

Table 19.15. INNODB_BUFFER_POOL_STATS Columns

Column nameDescription
POOL_ID 
POOL_SIZE 
FREE_BUFFERS 
DATABASE_PAGES 
OLD_DATABASE_PAGES 
MODIFIED_DATABASE_PAGES 
PENDING_DECOMPRESS 
PENDING_READS 
PENDING_FLUSH_LRU 
PENDING_FLUSH_LIST 
PAGES_MADE_YOUNG 
PAGES_NOT_MADE_YOUNG 
PAGES_MADE_YOUNG_RATE 
PAGES_MADE_NOT_YOUNG_RATE 
NUMBER_PAGES_READ 
NUMBER_PAGES_CREATED 
NUMBER_PAGES_WRITTEN 
PAGES_READ_RATE 
PAGES_CREATE_RATE 
PAGES_WRITTEN_RATE 
NUMBER_PAGES_GET 
HIT_RATE 
YOUNG_MAKE_PER_THOUSAND_GETS 
NOT_YOUNG_MAKE_PER_THOUSAND_GETS 
NUMBER_PAGES_READ_AHEAD 
NUMBER_READ_AHEAD_EVICTED 
READ_AHEAD_RATE 
REAT_AHEAD_EVICTED_RATE 
LRU_IO_TOTAL 
LRU_IO_CURRENT 
UNCOMPRESS_TOTAL 
UNCOMPRESS_CURRENT 

Notes:

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

  • Since the INFORMATION_SCHEMA is a general-purpose way to monitor the MySQL server, use this table rather than the corresponding InnoDB system table for any new monitoring application you develop.

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

19.30.17. The INFORMATION_SCHEMA INNODB_METRICS Table

This INFORMATION_SCHEMA table presents 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.

Table 19.16. INNODB_METRICS Columns

Column nameDescription
NAMEUnique name for the counter.
SUBSYSTEMThe aspect of InnoDB that the metric applies to. See the list following the table for the corresponding module names to use with the SET GLOBAL syntax.
COUNTValue since the counter is enabled.
MAX_COUNTMaximum value since the counter is enabled.
MIN_COUNTMinimum value since the counter is enabled.
AVG_COUNTAverage value since the counter is enabled.
COUNT_RESETCounter value since it was last reset. (The _RESET fields 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 the COUNT, MAX_COUNT, and so on fields.)
MAX_COUNT_RESETMaximum counter value since it was last reset.
MIN_COUNT_RESETMinimum counter value since it was last reset.
AVG_COUNT_RESETAverage counter value since it was last reset.
TIME_ENABLEDTimestamp of last start.
TIME_DISABLEDTimestamp of last stop.
TIME_ELAPSEDElapsed time in seconds since the counter started.
TIME_RESETTimestamp of last stop.
STATUSWhether the counter is still running () or stopped ().
TYPEWhether the item is a cumulative counter, or measures the current value of some resource.
COMMENTAdditional description.

Notes:

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

  • By default, relatively little data is collected. To start, stop, and reset counters, you set one of the the configuration options 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 example:

    -- Turn on a counter:
    set global innodb_monitor_enable = counter_name;
    -- Turn off a counter:
    set global innodb_monitor_disable = counter_name;
    -- Reset a counter:
    set global innodb_monitor_reset = counter_name;
    -- Reset all the counter values:
    set global innodb_monitor_reset_all = counter_name;
    -- Turn on a group of counters:
    set global innodb_monitor_enable = module_name;
    -- Turn off a group of counters:
    set global innodb_monitor_enable = module_name;
    -- Turn on monitor "dml_num_inserts":
    set global innodb_monitor_enable = dml_num_inserts;
    -- Reset all values for "dml_num_inserts":
    set global innodb_monitor_reset_all = dml_num_inserts;
    -- Reset the counters for all dml monitors
    set global innodb_monitor_reset = "dml_%";
    -- Turn on all monitors for the transaction subsystem
    set global innodb_monitor_enable = module_trx;
    -- Turn off all monitors
    set global innodb_monitor_disable = all;
    
  • The module names correspond to, but are not identical to, the values from the SUBSYSTEM column. Here are the values you can use for module_name with the innodb_monitor_enable and related configuration options, along with the corresponding SUBSYSTEM names:

    • module_metadata (subsystem = metadata)

    • module_lock (subsystem = lock)

    • module_buffer (subsystem = buffer)

    • module_buf_page (subsystem = buffer_page_io)

    • module_os (subsystem = os)

    • module_trx (subsystem = transaction)

    • module_purge (subsystem = purge)

    • module_compress (subsystem = compression)

    • module_file (subsystem = file_system)

    • module_index (subsystem = index)

    • module_adaptive_hash (subsystem = adaptive_hash_index)

    • module_ibuf_system (subsystem = change_buffer)

    • module_srv (subsystem = server)

    • module_ddl (subsystem = ddl)

    • module_dml (subsystem = dml)

    • module_log (subsystem = recovery)

    • module_icp (subsystem = icp)

  • Because each counter imposes some degree of runtime overhead on the server, typically you enable more counters on test and development servers during experimentation and benchmarking, and only enable counters on production servers to diagnose known issues or monitor aspects that are likely to be bottlenecks for a particular server and workload.

  • The items represented in the innodb_metrics table are subject to change, so for the most up-to-date list, query a running MySQL server. As of MySQL 5.6.10, the items include:

    mysql: select name, subsystem from information_schema.innodb_metrics order by name;
    +------------------------------------------+---------------------+
    | name                                     | subsystem           |
    +------------------------------------------+---------------------+
    | adaptive_hash_pages_added                | adaptive_hash_index |
    | adaptive_hash_pages_removed              | adaptive_hash_index |
    | adaptive_hash_rows_added                 | adaptive_hash_index |
    | adaptive_hash_rows_deleted_no_hash_entry | adaptive_hash_index |
    | adaptive_hash_rows_removed               | adaptive_hash_index |
    | adaptive_hash_rows_updated               | adaptive_hash_index |
    | adaptive_hash_searches                   | adaptive_hash_index |
    | adaptive_hash_searches_btree             | adaptive_hash_index |
    | buffer_data_reads                        | buffer              |
    | buffer_data_written                      | buffer              |
    | buffer_flush_adaptive                    | buffer              |
    | buffer_flush_adaptive_pages              | buffer              |
    | buffer_flush_adaptive_total_pages        | buffer              |
    | buffer_flush_avg_page_rate               | buffer              |
    | buffer_flush_background                  | buffer              |
    | buffer_flush_background_pages            | buffer              |
    | buffer_flush_background_total_pages      | buffer              |
    | buffer_flush_batches                     | buffer              |
    | buffer_flush_batch_num_scan              | buffer              |
    | buffer_flush_batch_pages                 | buffer              |
    | buffer_flush_batch_scanned               | buffer              |
    | buffer_flush_batch_scanned_per_call      | buffer              |
    | buffer_flush_batch_total_pages           | buffer              |
    | buffer_flush_lsn_avg_rate                | buffer              |
    | buffer_flush_neighbor                    | buffer              |
    | buffer_flush_neighbor_pages              | buffer              |
    | buffer_flush_neighbor_total_pages        | buffer              |
    | buffer_flush_n_to_flush_requested        | buffer              |
    | buffer_flush_pct_for_dirty               | buffer              |
    | buffer_flush_pct_for_lsn                 | buffer              |
    | buffer_flush_sync                        | buffer              |
    | buffer_flush_sync_pages                  | buffer              |
    | buffer_flush_sync_total_pages            | buffer              |
    | buffer_flush_sync_waits                  | buffer              |
    | buffer_LRU_batches                       | buffer              |
    | buffer_LRU_batch_num_scan                | buffer              |
    | buffer_LRU_batch_pages                   | buffer              |
    | buffer_LRU_batch_scanned                 | buffer              |
    | buffer_LRU_batch_scanned_per_call        | buffer              |
    | buffer_LRU_batch_total_pages             | buffer              |
    | buffer_LRU_get_free_search               | Buffer              |
    | buffer_LRU_search_num_scan               | buffer              |
    | buffer_LRU_search_scanned                | buffer              |
    | buffer_LRU_search_scanned_per_call       | buffer              |
    | buffer_LRU_single_flush_failure_count    | Buffer              |
    | buffer_LRU_single_flush_num_scan         | buffer              |
    | buffer_LRU_single_flush_scanned          | buffer              |
    | buffer_LRU_single_flush_scanned_per_call | buffer              |
    | buffer_LRU_unzip_search_num_scan         | buffer              |
    | buffer_LRU_unzip_search_scanned          | buffer              |
    | buffer_LRU_unzip_search_scanned_per_call | buffer              |
    | buffer_pages_created                     | buffer              |
    | buffer_pages_read                        | buffer              |
    | buffer_pages_written                     | buffer              |
    | buffer_page_read_blob                    | buffer_page_io      |
    | buffer_page_read_fsp_hdr                 | buffer_page_io      |
    | buffer_page_read_ibuf_bitmap             | buffer_page_io      |
    | buffer_page_read_ibuf_free_list          | buffer_page_io      |
    | buffer_page_read_index_ibuf_leaf         | buffer_page_io      |
    | buffer_page_read_index_ibuf_non_leaf     | buffer_page_io      |
    | buffer_page_read_index_inode             | buffer_page_io      |
    | buffer_page_read_index_leaf              | buffer_page_io      |
    | buffer_page_read_index_non_leaf          | buffer_page_io      |
    | buffer_page_read_other                   | buffer_page_io      |
    | buffer_page_read_system_page             | buffer_page_io      |
    | buffer_page_read_trx_system              | buffer_page_io      |
    | buffer_page_read_undo_log                | buffer_page_io      |
    | buffer_page_read_xdes                    | buffer_page_io      |
    | buffer_page_read_zblob                   | buffer_page_io      |
    | buffer_page_read_zblob2                  | buffer_page_io      |
    | buffer_page_written_blob                 | buffer_page_io      |
    | buffer_page_written_fsp_hdr              | buffer_page_io      |
    | buffer_page_written_ibuf_bitmap          | buffer_page_io      |
    | buffer_page_written_ibuf_free_list       | buffer_page_io      |
    | buffer_page_written_index_ibuf_leaf      | buffer_page_io      |
    | buffer_page_written_index_ibuf_non_leaf  | buffer_page_io      |
    | buffer_page_written_index_inode          | buffer_page_io      |
    | buffer_page_written_index_leaf           | buffer_page_io      |
    | buffer_page_written_index_non_leaf       | buffer_page_io      |
    | buffer_page_written_other                | buffer_page_io      |
    | buffer_page_written_system_page          | buffer_page_io      |
    | buffer_page_written_trx_system           | buffer_page_io      |
    | buffer_page_written_undo_log             | buffer_page_io      |
    | buffer_page_written_xdes                 | buffer_page_io      |
    | buffer_page_written_zblob                | buffer_page_io      |
    | buffer_page_written_zblob2               | buffer_page_io      |
    | buffer_pool_bytes_data                   | buffer              |
    | buffer_pool_bytes_dirty                  | buffer              |
    | buffer_pool_pages_data                   | buffer              |
    | buffer_pool_pages_dirty                  | buffer              |
    | buffer_pool_pages_free                   | buffer              |
    | buffer_pool_pages_misc                   | buffer              |
    | buffer_pool_pages_total                  | buffer              |
    | buffer_pool_reads                        | buffer              |
    | buffer_pool_read_ahead                   | buffer              |
    | buffer_pool_read_ahead_evicted           | buffer              |
    | buffer_pool_read_requests                | buffer              |
    | buffer_pool_size                         | server              |
    | buffer_pool_wait_free                    | buffer              |
    | buffer_pool_write_requests               | buffer              |
    | compression_pad_decrements               | compression         |
    | compression_pad_increments               | compression         |
    | compress_pages_compressed                | compression         |
    | compress_pages_decompressed              | compression         |
    | ddl_background_drop_indexes              | ddl                 |
    | ddl_background_drop_tables               | ddl                 |
    | ddl_online_create_index                  | ddl                 |
    | ddl_pending_alter_table                  | ddl                 |
    | dml_deletes                              | dml                 |
    | dml_inserts                              | dml                 |
    | dml_reads                                | dml                 |
    | dml_updates                              | dml                 |
    | file_num_open_files                      | file_system         |
    | ibuf_merges                              | change_buffer       |
    | ibuf_merges_delete                       | change_buffer       |
    | ibuf_merges_delete_mark                  | change_buffer       |
    | ibuf_merges_discard_delete               | change_buffer       |
    | ibuf_merges_discard_delete_mark          | change_buffer       |
    | ibuf_merges_discard_insert               | change_buffer       |
    | ibuf_merges_insert                       | change_buffer       |
    | ibuf_size                                | change_buffer       |
    | icp_attempts                             | icp                 |
    | icp_match                                | icp                 |
    | icp_no_match                             | icp                 |
    | icp_out_of_range                         | icp                 |
    | index_merges                             | index               |
    | index_splits                             | index               |
    | innodb_activity_count                    | server              |
    | innodb_background_drop_table_usec        | server              |
    | innodb_checkpoint_usec                   | server              |
    | innodb_dblwr_pages_written               | server              |
    | innodb_dblwr_writes                      | server              |
    | innodb_dict_lru_usec                     | server              |
    | innodb_ibuf_merge_usec                   | server              |
    | innodb_log_flush_usec                    | server              |
    | innodb_master_active_loops               | server              |
    | innodb_master_idle_loops                 | server              |
    | innodb_master_purge_usec                 | server              |
    | innodb_master_thread_sleeps              | server              |
    | innodb_mem_validate_usec                 | server              |
    | innodb_page_size                         | server              |
    | innodb_rwlock_s_os_waits                 | server              |
    | innodb_rwlock_s_spin_rounds              | server              |
    | innodb_rwlock_s_spin_waits               | server              |
    | innodb_rwlock_x_os_waits                 | server              |
    | innodb_rwlock_x_spin_rounds              | server              |
    | innodb_rwlock_x_spin_waits               | server              |
    | lock_deadlocks                           | lock                |
    | lock_rec_locks                           | lock                |
    | lock_rec_lock_created                    | lock                |
    | lock_rec_lock_removed                    | lock                |
    | lock_rec_lock_requests                   | lock                |
    | lock_rec_lock_waits                      | lock                |
    | lock_row_lock_current_waits              | lock                |
    | lock_row_lock_time                       | lock                |
    | lock_row_lock_time_avg                   | lock                |
    | lock_row_lock_time_max                   | lock                |
    | lock_row_lock_waits                      | lock                |
    | lock_table_locks                         | lock                |
    | lock_table_lock_created                  | lock                |
    | lock_table_lock_removed                  | lock                |
    | lock_table_lock_waits                    | lock                |
    | lock_timeouts                            | lock                |
    | log_checkpoints                          | recovery            |
    | log_lsn_buf_pool_oldest                  | recovery            |
    | log_lsn_checkpoint_age                   | recovery            |
    | log_lsn_current                          | recovery            |
    | log_lsn_last_checkpoint                  | recovery            |
    | log_lsn_last_flush                       | recovery            |
    | log_max_modified_age_async               | recovery            |
    | log_max_modified_age_sync                | recovery            |
    | log_num_log_io                           | recovery            |
    | log_pending_checkpoint_writes            | recovery            |
    | log_pending_log_writes                   | recovery            |
    | log_waits                                | recovery            |
    | log_writes                               | recovery            |
    | log_write_requests                       | recovery            |
    | metadata_mem_pool_size                   | metadata            |
    | metadata_table_handles_closed            | metadata            |
    | metadata_table_handles_opened            | metadata            |
    | metadata_table_reference_count           | metadata            |
    | os_data_fsyncs                           | os                  |
    | os_data_reads                            | os                  |
    | os_data_writes                           | os                  |
    | os_log_bytes_written                     | os                  |
    | os_log_fsyncs                            | os                  |
    | os_log_pending_fsyncs                    | os                  |
    | os_log_pending_writes                    | os                  |
    | os_pending_reads                         | os                  |
    | os_pending_writes                        | os                  |
    | purge_del_mark_records                   | purge               |
    | purge_dml_delay_usec                     | purge               |
    | purge_invoked                            | purge               |
    | purge_resume_count                       | purge               |
    | purge_stop_count                         | purge               |
    | purge_undo_log_pages                     | purge               |
    | purge_upd_exist_or_extern_records        | purge               |
    | trx_active_transactions                  | transaction         |
    | trx_commits_insert_update                | transaction         |
    | trx_nl_ro_commits                        | transaction         |
    | trx_rollbacks                            | transaction         |
    | trx_rollbacks_savepoint                  | transaction         |
    | trx_rollback_active                      | transaction         |
    | trx_ro_commits                           | transaction         |
    | trx_rseg_current_size                    | transaction         |
    | trx_rseg_history_len                     | transaction         |
    | trx_rw_commits                           | transaction         |
    | trx_undo_slots_cached                    | transaction         |
    | trx_undo_slots_used                      | transaction         |
    +------------------------------------------+---------------------+
    209 rows in set (0.00 sec)

19.30.18. The INFORMATION_SCHEMA INNODB_FT_CONFIG Table

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

This table is only accessible to users with the SUPER privilege. Before you query this table, set the configuration variable innodb_ft_aux_table to the name (including the database name) of the table that contains the FULLTEXT index, for example test/articles.

Table 19.17. INNODB_FT_CONFIG Columns

Column nameDescription
KEYThe name designating an item of metadata for an InnoDB table containing a FULLTEXT index.
VALUEThe value associated with the corresponding KEY column, reflecting some limit or current value for an aspect of a FULLTEXT index for an InnoDB table.

Notes:

  • This table initially appears empty, until you set the value of the configuration variable innodb_ft_aux_table.

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

  • The values for the KEY column might evolve depending on the needs for performance tuning and debugging for InnoDB full-text processing. Currently, the key values include optimize_checkpoint_limit, synced_doc_id, last_optimized_word, deleted_doc_count, total_word_count, optimize_start_time, optimize_end_time, stopword_table_name, use_stopword, and table_state.

  • For more information, see Section 12.9, “Full-Text Search Functions”.

19.30.19. 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 an InnoDB table.

Table 19.18. INNODB_FT_DEFAULT_STOPWORD Columns

Column nameDescription
valueA word that is used by default as a stopword for FULLTEXT indexes on InnoDB tables. Not used if you override the default stopword processing with either the innodb_ft_server_stopword_table or the innodb_ft_user_stopword_table option.

Notes:

19.30.20. The INFORMATION_SCHEMA INNODB_FT_INDEX_TABLE Table

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

This table is only accessible to users with the SUPER privilege. Before you query this table, set the configuration variable innodb_ft_aux_table to the name (including the database name) of the table that contains the FULLTEXT index, for example test/articles.

Table 19.19. INNODB_FT_INDEX_TABLE Columns

Column nameDescription
WORDA word extracted from the text of the columns that are part of a FULLTEXT.
FIRST_DOC_IDThe first document ID that this word appears in in the FULLTEXT index.
LAST_DOC_IDThe last document ID that this word appears in in the FULLTEXT index.
DOC_COUNTThe number of rows this word appears in 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_IDThe 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 does not contain a suitable column.
POSITIONThe position of this particular instance of the word within the relevant document identified by the DOC_ID value.

Notes:

19.30.21. The INFORMATION_SCHEMA INNODB_FT_INDEX_CACHE Table

The INNODB_FT_INDEX_CACHE table displays token information about newly inserted rows in a FULLTEXT index for an InnoDB table. To avoid expensive index reorganization during DML operations for an InnoDB FULLTEXT index, the information about newly indexed words is stored separately, and combined with the main search index only when you issue the OPTIMIZE TABLE statement for the InnoDB table.

This table is only accessible to users with the SUPER privilege. Before you query this table, set the configuration variable innodb_ft_aux_table to the name (including the database name) of the table that contains the FULLTEXT index, for example test/articles.

Table 19.20. INNODB_FT_INDEX_CACHE Columns

Column nameDescription
WORDA word extracted from the text of a newly inserted row.
FIRST_DOC_IDThe first document ID that this word appears in in the FULLTEXT index.
LAST_DOC_IDThe last document ID that this word appears in in the FULLTEXT index.
DOC_COUNTThe number of rows this word appears in 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_IDThe 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 does not contain a suitable column.
POSITIONThe 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:

19.30.22. The INFORMATION_SCHEMA INNODB_FT_INSERTED Table

The INNODB_FT_INSERTED table contains a list of IDs for newly inserted rows, for an InnoDB table with a FULLTEXT index. These IDs refer to corresponding values within the innodb_ft_index_table and innodb_ft_index_cache tables. (When you issue an OPTIMIZE TABLE statement for the InnoDB table containing the FULLTEXT index, the IDs are transferred from the cache table to the table that represents the index.)

This table is only accessible to users with the SUPER privilege. Before you query this table, set the configuration variable innodb_ft_aux_table to the name (including the database name) of the table that contains the FULLTEXT index, for example test/articles.

Table 19.21. INNODB_FT_INSERTED Columns

Column nameDescription
DOC_IDThe 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 does not contain a suitable column. This value is used to look up rows in the innodb_ft_index_cache table, when you do text searches before the data is merged into the FULLTEXT index by an OPTIMIZE TABLE statement.

Notes:

19.30.23. The INFORMATION_SCHEMA INNODB_FT_DELETED Table

The INNODB_FT_DELETED table records 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 the OPTIMIZE TABLE statement for the InnoDB table.

This table is only accessible to users with the SUPER privilege. Before you query this table, set the configuration variable innodb_ft_aux_table to the name (including the database name) of the table that contains the FULLTEXT index, for example test/articles.

Table 19.22. INNODB_FT_DELETED Columns

Column nameDescription
DOC_IDThe 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 does not contain a suitable column. This value is used to skip rows in the innodb_ft_index_table table, when you do text searches before data for deleted rows is physically removed from the FULLTEXT index by an OPTIMIZE TABLE statement.

Notes:

19.30.24. The INFORMATION_SCHEMA INNODB_FT_BEING_DELETED Table

The INNODB_FT_BEING_DELETED table is a temporary work table while document IDs in the INNODB_FT_DELETED table are being removed from an InnoDB FULLTEXT index during an OPTIMIZE TABLE operation. Because its contents typically have a short lifetime, this table has limited utility for monitoring or debugging.

This table is only accessible to users with the SUPER privilege. This table initially appears empty, until you set the value of the configuration variable innodb_ft_aux_table.

Table 19.23. INNODB_FT_BEING_DELETED Columns

Column nameDescription
DOC_IDThe 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 does not contain a suitable column. This value is used to skip rows in the innodb_ft_index_table table, when you do text searches before data for deleted rows is physically removed from the FULLTEXT index by an OPTIMIZE TABLE statement.

Notes:

19.31. Thread Pool INFORMATION_SCHEMA Tables

The following sections describe the INFORMATION_SCHEMA tables associated with the thread pool plugin. 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 8.11.6.1, “Thread Pool Components and 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.

19.31.1. The INFORMATION_SCHEMA TP_THREAD_STATE Table

This table has one row per thread created by the thread pool to handle connections. The 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 19.24. WAIT_TYPE Values

    Wait TypeMeaning
    THD_WAIT_SLEEPWaiting for sleep
    THD_WAIT_DISKIOWaiting for Disk IO
    THD_WAIT_ROW_LOCKWaiting for row lock
    THD_WAIT_GLOBAL_LOCKWaiting for global lock
    THD_WAIT_META_DATA_LOCKWaiting for metadata lock
    THD_WAIT_TABLE_LOCKWaiting for table lock
    THD_WAIT_USER_LOCKWaiting for user lock
    THD_WAIT_BINLOGWaiting for binlog
    THD_WAIT_GROUP_COMMITWaiting for group commit
    THD_WAIT_SYNCWaiting for fsync

19.31.2. The INFORMATION_SCHEMA TP_THREAD_GROUP_STATE Table

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

  • 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 variable on the thread group. This is the same value for all thread groups.

  • PRIO_KICKUP_TIMER

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

  • ALGORITHM

    The value of the thread_pool_algorithm on 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 executing statements.

  • 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_GROUP_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;
  • 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.

19.31.3. The INFORMATION_SCHEMA TP_THREAD_GROUP_STATS Table

This table reports statistics per thread group. There is one row per group. The 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 8.11.6.2, “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 a time 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.

19.32. 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                                 |
+---------------------------------------+
27 rows in set (0.00 sec)

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 multi-byte 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 |
+---------+---------------------------+---------------------+--------+