Bug #92012 Wrong default for thread_cache_size in "How MySQL Uses Threads for Client Cnx".
Submitted: 14 Aug 2018 14:47 Modified: 15 Aug 2018 21:59
Reporter: Jean-François Gagné Email Updates:
Status: Closed Impact on me:
None 
Category:MySQL Server: Documentation Severity:S3 (Non-critical)
Version:8.0, 5.7, 5.6 OS:Any
Assigned to: CPU Architecture:Any

[14 Aug 2018 14:47] Jean-François Gagné 
Description:
Hi,

In [1], I can read "The thread cache has a size determined by the thread_cache_size system variable. The default value is 0 (no caching), which causes a thread to be set up for each new connection and disposed of when the connection terminates.".

[1]: https://dev.mysql.com/doc/refman/8.0/en/connection-threads.html

However in [2], I can read that "The default value is based on the following formula [...]".

[2]: https://dev.mysql.com/doc/refman/8.0/en/server-system-variables.html#sysvar_thread_cache_s...

It looks like [1] was not updated when the default value was changed.  This change was done in MySQL 5.6 ([3]), so in addition to [1], [4] and [5] should also be fixed.

[3]: https://dev.mysql.com/doc/refman/5.6/en/server-system-variables.html#sysvar_thread_cache_s...

[4]: https://dev.mysql.com/doc/refman/5.7/en/connection-threads.html

[5]: https://dev.mysql.com/doc/refman/5.6/en/connection-threads.html

Many thanks for looking into that,

JFG

How to repeat:
See description.
[15 Aug 2018 6:46] MySQL Verification Team 
Hello Jean-François,

Thank you for the report!

regards,
Umesh
[15 Aug 2018 21:59] Paul DuBois 
Posted by developer:
 
Updated. Thanks for spotting this!