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10.12.2 The table_handles Table

The Performance Schema exposes table lock information through the table_handles table to show the table locks currently in effect for each opened table handle. table_handles reports what is recorded by the table lock instrumentation. This information shows which table handles the server has open, how they are locked, and by which sessions.

The table_handles table is read only and cannot be updated. It is autosized by default; to configure the table size, set the performance_schema_max_table_handles system variable at server startup.

The table_handles table has these columns:


    The table opened by a table handle.


    The schema that contains the object.


    The name of the instrumented object.


    The table handle address in memory.


    The thread owning the table handle.


    The event which caused the table handle to be opened.


    The table lock used at the SQL level. The value is one of READ, READ WITH SHARED LOCKS, READ HIGH PRIORITY, READ NO INSERT, WRITE ALLOW WRITE, WRITE CONCURRENT INSERT, WRITE LOW PRIORITY, or WRITE. For information about these lock types, see the include/thr_lock.h source file.


    The table lock used at the storage engine level. The value is one of READ EXTERNAL or WRITE EXTERNAL.

TRUNCATE TABLE is not permitted for the table_handles table.

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