Details
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Bug
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Status: Closed (View Workflow)
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Critical
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Resolution: Won't Fix
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N/A
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None
Description
MDEV-33501 adds a new variable QUERY_RESPONSE_TIME_SESSION_STATS.
If I understand the description correctly, it can be set to ON or OFF for the session, in which case it will work accordingly, regardless of QUERY_RESPONSE_TIME_STATS; or it can be set to GLOBAL in which case QUERY_RESPONSE_TIME_STATS will control whether the stats are collected or not.
If this is correct, I see no purpose to have the variable. It is a behavior of a standard session+global variable of which we have plenty in the server: if @@session.xxx is set to ON and OFF, it works accordingly, and if it is set to DEFAULT, the value of @@global.xxx is used.
So, instead of adding a new variable, the scope of QUERY_RESPONSE_TIME_STATS should be extended to make it both session and global.
If there is a reason why it cannot be done so, please elaborate for the documentation purposes why the new variable is needed, and move the ticket to documentation.
Attachments
Issue Links
- is caused by
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MDEV-33501 Extend query_response_time plugin to be compatible with Percona server
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- Closed
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Activity
What we could do in the the future is to add a way to change all running user's thd bool variables at once (for some variables like query_response_session_stats).
If we would have that, we would then not have a need for query_response_session_time_stats.
Until we have a way to affect all running THD users at once, we are better of with Percona's solution.
I agree that this needs to be documented properly
There are two benefits of the current solution:
By setting @query_response_session_time_stats=global in a config file, a DBA can turn all the statistics ON or OFF instantly.
Doing things the 'normal way' (having query_response_time_stats a global and session variable) would only affect the users when they connect the next time.
By default the variable is global, which means that a DB can enable and disable logging of all queries at any point in time. I think that is probably something that they will like.