Bug #93636 Documentation incorrect on when data purged from events_statements_history_long

• Submitted: 17 Dec 2018 9:30
• Modified: 18 Dec 2018 14:58
• Reporter: Mark Leith
• Status: Closed
• Category: MySQL Server: Documentation
• Severity: S3 (Non-critical)
• OS: Any
• CPU Architecture: Any

[17 Dec 2018 9:30] Mark Leith

Description:
The documentation for the Performance Schema statement history tables states :

“When a thread ends, all its rows are discarded from both history tables.”

https://dev.mysql.com/doc/refman/5.7/en/performance-schema-event-tables.html

This is incorrect, when a thread ends all of the data is discarded from the _history table(s), but the data is maintained within the _history_long table(s).

How to repeat:
Execute a statement from a session, close that session, check whether the statement is visible within performance_schema.events_statements_history_long.

Suggested fix:
Update the docs to reflect that only the _history table (per thread data) is purged when connections disconnect, history_long (global data) is maintained.

[17 Dec 2018 14:21] Derek Downey

This probably goes without saying, but the docs should also be updated on the specific events_XXX_history_long pages. eg:

https://dev.mysql.com/doc/refman/5.7/en/events-waits-history-long-table.html
https://dev.mysql.com/doc/refman/5.7/en/events-statements-history-long-table.html

both mention this at the end of the first paragraph: 

"When a thread ends, all its rows are discarded."

[18 Dec 2018 14:58] Paul DuBois

Posted by developer:
 
Updated the docs for _history_long tables. Thanks for pointing out the problem.