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Missing MySQL statistics and performance_schema.events_statements_summary_by_digest table is full error in the log file

Created by Anthony.Rinaldi_ret, last modified by MindTouch on Jun 23, 2016

Views: 43 Votes: 0 Revisions: 2

Overview

The DPA log contains a statement like this:

The performance_schema.events_statements_summary_by_digest table is full, some statistics [73 executions] will be lost. Please see the following KB article for more information.

Environment

  • All versions of DPA

Cause 

MySQL statistics are calculated by querying the performance_schema.events_statements_summary_by_digest table. This table has a fixed size that can be changed, but when the table becomes full, any new values not already in the table get grouped in a special NULL row. This allows MySQL to still account for statistics, however it may represent multiple DIGESTS and DPA cannot report which DIGESTS accounted for the changes.

If DPA determines that there is a NULL row within the events_statements_summary_by_digest table that is accumulating statistics, it will report it in the DPA logs. 

Resolution

To get accurate statistics in DPA, it may be desirable to increase the size of the events_statements_summary_by_digest table in your MySQL instance. This can be done by setting the performance_schema_digests_size system variable to a larger value in the my.ini or my.cnf file and restarting your MySQL service.

performance_schema_digests_size=12000

To see the current value or to ensure that your change was honored, you can issue the following SQL:

mysql> SHOW VARIABLES LIKE 'performance_schema_digests_size%';

Example Result:

+---------------------------------+-------+

| Variable_name                   | Value |

+---------------------------------+-------+

| performance_schema_digests_size | 10000 |

+---------------------------------+-------+

 

 

 

 

Last modified
19:16, 22 Jun 2016

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