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15.14.7 InnoDB INFORMATION_SCHEMA Temporary Table Info Table

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INNODB_TEMP_TABLE_INFO provides information about user-created InnoDB temporary tables that are active in the InnoDB instance. It does not provide information about internal InnoDB temporary tables used by the optimizer.

  1. mysql> SHOW TABLES FROM INFORMATION_SCHEMA LIKE 'INNODB_TEMP%';
  2. +---------------------------------------------+
  3. | Tables_in_INFORMATION_SCHEMA (INNODB_TEMP%) |
  4. +---------------------------------------------+
  5. | INNODB_TEMP_TABLE_INFO                      |
  6. +---------------------------------------------+

For the table definition, see Section 25.39.28, “The INFORMATION_SCHEMA INNODB_TEMP_TABLE_INFO Table”.

Example 15.12 INNODB_TEMP_TABLE_INFO

This example demonstrates characteristics of the INNODB_TEMP_TABLE_INFO table.

  1. Create a simple InnoDB temporary table:

    1. mysql> CREATE TEMPORARY TABLE t1 (c1 INT PRIMARY KEY) ENGINE=INNODB;

  2. Query INNODB_TEMP_TABLE_INFO to view the temporary table metadata.

    1. mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_TEMP_TABLE_INFO\G
    2. *************************** 1. row ***************************
    3.             TABLE_ID: 194
    4.                 NAME: #sql7a79_1_0
    5.               N_COLS: 4
    6.                SPACE: 182

    The TABLE_ID is a unique identifier for the temporary table. The NAME column displays the system-generated name for the temporary table, which is prefixed with “#sql”. The number of columns (N_COLS) is 4 rather than 1 because InnoDB always creates three hidden table columns (DB_ROW_ID, DB_TRX_ID, and DB_ROLL_PTR).

  3. Restart MySQL and query INNODB_TEMP_TABLE_INFO.

    1. mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_TEMP_TABLE_INFO\G

    An empty set is returned because INNODB_TEMP_TABLE_INFO and its data are not persisted to disk when the server is shut down.

  4. Create a new temporary table.

    1. mysql> CREATE TEMPORARY TABLE t1 (c1 INT PRIMARY KEY) ENGINE=INNODB;

  5. Query INNODB_TEMP_TABLE_INFO to view the temporary table metadata.

    1. mysql> SELECT * FROM INFORMATION_SCHEMA.INNODB_TEMP_TABLE_INFO\G
    2. *************************** 1. row ***************************
    3.             TABLE_ID: 196
    4.                 NAME: #sql7b0e_1_0
    5.               N_COLS: 4
    6.                SPACE: 184

    The SPACE ID may be different because it is dynamically generated when the server is started.



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Document created the 26/06/2006, last modified the 26/10/2018
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