MySQL Bugs: #104582: fts_optimize_thread missing in performance

Bug #104582	fts_optimize_thread missing in performance_schema.threads
Submitted:	10 Aug 2021 13:44	Modified:	6 Oct 2021 11:18
Reporter:	Kaige Ye (OCA)	Email Updates:
Status:	Closed	Impact on me:	None
Category:	MySQL Server: Performance Schema	Severity:	S3 (Non-critical)
Version:	5.7	OS:	Any
Assigned to:	Marc ALFF	CPU Architecture:	Any

Description:
The `fts_optimize_thread` should be in the performance_schema.threads table.

How to repeat:
select thread_id,name,thread_os_id from performance_schema.threads;

Suggested fix:
A `pfs_register_thread()` call is missing in `fts_optimize_thread()`.

Here is the fix: https://github.com/mysql/mysql-server/pull/349

Hi Mr. Ye,

Thank you for your bug report.

We find your feature request quite interesting. This is we verify your report as a feature request. Since all new features go into 8.0, we change the version to 8.0.

Verified as a feature request.

(Un)fortunately version 8.0 doesn't have this issue, but version 5.7 does have.

The doc says "The threads table contains a row for each server thread".
https://dev.mysql.com/doc/refman/5.7/en/performance-schema-threads-table.html

Should we think it should be a feature and not a bug? Because if I started mysqld with gdb, I can always confirm that `fts_optimize_thread` and `buf_resize_thread` was alive, but both of them can't been seen in `performance_schema`.`threads` table. 

Under gdb, with `info threads`, I can confirm there are 28 threads, but P_S.`threads` only have 26 threads.

Contribution submitted via Github - fix fts_optimize_thread missing in performance_schema.threads (*) Contribution by Kaige Ye (Github YKG, mysql-server/pull/363#issuecomment-907067896): I confirm the code being submitted is offered under the terms of the OCA, and that I am authorized to contribute it.

Contribution: git_patch_720970102.txt (text/plain), 2.62 KiB.

To clarify,

incomplete performance_schema instrumentation is considered a bug,
because it affects the quality of stats returned by the performance schema.

Posted by developer:
 
Noted in 5.7.36 and 8.0.27 changelogs
The following threads are now present in the performance_schema.threads table:
 
- buf_resize_thread
- fts_optimize_thread
          
Thanks to Kaige Ye for the contribution.

Posted by developer:
 
text updated for 8.0.27 only.