21.6. Performance Schema General Table Characteristics

The database name performance_schema is lowercase. The names of tables in the database are uppercase. Normal case sensitivity rules apply, so on systems with case-sensitive file names, the database name and table names must be specified in the lettercase just indicated. This behavior can be modified by setting the lower_case_table_names system variable.

Most tables in the performance_schema database are read only and cannot be modified. Some of the setup tables have columns that can be modified to affect Performance Schema operation. Truncation is permitted to clear collected events, so TRUNCATE TABLE can be used on tables containing those kinds of information, such as tables named with a prefix of events_waits_.

TRUNCATE TABLE can also be used with summary tables, but the effect is to reset the summary columns to 0 or NULL, not to remove rows.

Privileges are as for other databases and tables:

  • To retrieve from performance_schema tables, you must have the SELECT privilege.

  • To change those columns that can be modified, you must have the UPDATE privilege.

  • To truncate tables that can be truncated, you must have the DROP privilege.

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