Re: bt_index_parent_check and concurrently build indexes

Donghang Lin <donghanglin@gmail.com>

From: Donghang Lin <donghanglin@gmail.com>

To: Michail Nikolaev <michail.nikolaev@gmail.com>

Cc: "Andrey M. Borodin" <x4mmm@yandex-team.ru>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>

Date: 2025-06-03T00:40:18Z

Lists: pgsql-hackers

Commits

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amcheck: Fix snapshot usage in bt_index_parent_check
- e1a327dc4dcb 17.8 landed
- dcddd6987197 15.16 landed
- 607a67c5e657 14.21 landed
- 3c83a2a0ace9 18.2 landed
- 1f28982e4094 19 (unreleased) landed
- 098a1fab8a9b 16.12 landed
- df93f94dda51 18.2 landed
- ce2f575b7cf4 17.8 landed
- 6bd469d26aca 19 (unreleased) landed
Teach contrib/amcheck to check the unique constraint violation
- 5ae2087202af 17.0 cited

Hi Michail

> It turns out that bt_index_parent_check is not suitable for
validating indexes built concurrently.
Your finding is right on point! We recently used bt_index_parent_check to
verify concurrently built indexes in a concurrent workload,
bt_index_parent_check often gave such false positive error.

- indexinfo->ii_Concurrent = !state->readonly;
+ indexinfo->ii_Concurrent = true;

One suggestion to this change is that we might need to update the amcheck
doc to reflect that
"This consists of a “dummy” CREATE INDEX CONCURRENTLY operation" rather
than "CREATE INDEX" operation.

Regards,
Donghang