Bug #90840 1198 error message provides brainless suggestion

• Submitted: 11 May 2018 16:52
• Modified: 21 Jun 2018 10:45
• Reporter: Federico Razzoli (OCA)
• Status: Verified
• Category: MySQL Server: Errors
• Severity: S3 (Non-critical)
• Version: 5.6
• OS: Any
• CPU Architecture: Any

[11 May 2018 16:52] Federico Razzoli

Description:
I realised for the first time that MySQL suggests users to stop replication in order to be able to create unpredictable data inconsistencies:

mysql> SET GLOBAL sql_slave_skip_counter = 1;
ERROR 1198 (HY000): This operation cannot be performed with a running slave; run STOP SLAVE first

How to repeat:
See above

[11 May 2018 17:10] MySQL Verification Team

Thank you for the bug report. Please read? https://bugs.mysql.com/bug.php?id=77187.

[11 May 2018 17:39] Federico Razzoli

Ack. I didn't notice that the error changed, so this report only applies to 5.6.
At this point I'm not even sure it should be changed, since 5.6 is well-established version.

[12 May 2018 16:30] MySQL Verification Team

Thank you for the bug report. Well I could say !bug like it was for 5.7+, however let to development to decide that. Thanks.

[15 May 2018 7:59] Sven Sandberg

Sorry, I can't understand what kind of "unpredictable data inconsistencies"
you are seeing. Please, provide an example!

[15 May 2018 8:30] Federico Razzoli

Are you really asking why stopping a running slave to skip an event will produce inconsistencies? :)

[18 May 2018 8:46] Sven Sandberg

Oh, ok I think I see your point - sorry, I'm brainless too :) I thought you were suggesting that SET sql_slave_skip_counter should be allowed on a running slave.
But the point is really that STOP SLAVE will stop at a nondeterministic point so the "advice" is wrong.

[18 May 2018 8:49] Federico Razzoli

Yes, I confirm that this is exactly my point. :)