Horton

Re: Conflict detection and logging in logical replication

Michail Nikolaev <michail.nikolaev@gmail.com>

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From: Michail Nikolaev <michail.nikolaev@gmail.com>
To: Amit Kapila <amit.kapila16@gmail.com>
Cc: "Zhijie Hou (Fujitsu)" <houzj.fnst@fujitsu.com>, "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>, shveta malik <shveta.malik@gmail.com>, Nisha Moond <nisha.moond412@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Dilip Kumar <dilipbalaut@gmail.com>, Jan Wieck <jan@wi3ck.info>, Ashutosh Bapat <ashutosh.bapat.oss@gmail.com>
Date: 2024-08-16T11:46:45Z
Lists: pgsql-hackers 
Hello!

> I think you might misunderstand the behavior of CheckAndReportConflict(),
even
> if it found a conflict, it still inserts the tuple into the index which
means
> the change is anyway applied.

> In the above conditions where a concurrent tuple insertion is removed
> or rolled back before CheckAndReportConflict, the tuple inserted by
> apply will remain. There is no need to report anything in such cases
> as apply was successful.

Yes, thank you for explanation, I was thinking UNIQUE_CHECK_PARTIAL works
differently.

But now I think DirtySnapshot-related bug is a blocker for this feature
then, I'll reply into original after rechecking it.

Best regards,
Mikhail.

Commits

  1. Rename the conflict types for the origin differ cases.

  2. Doc: explain the log format of logical replication conflicts.

  3. Log the conflicts while applying changes in logical replication.

  4. Avoid duplicate table scans for cross-partition updates during logical replication.