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CREATE INDEX CONCURRENTLY does not index prepared xact's data

Andrey Borodin <x4mmm@yandex-team.ru>

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From: Andrey Borodin <x4mmm@yandex-team.ru>
To: pgsql-bugs@lists.postgresql.org
Date: 2020-12-19T17:13:39Z
Lists: pgsql-bugs

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Hi hackers!

$subj.

Steps to reproduce:
create extension if not exists amcheck;
create table if not exists t1(i int);
begin;
insert into t1 values(1);
prepare transaction 'x';
create index concurrently i1 on t1(i); 
commit prepared 'x';
select bt_index_check('i1', true);

I observe:
NOTICE:  heap tuple (1,8) from table "t1" lacks matching index tuple within index "i1"
I expect: awaiting 'x' commit before index is created, correct index after.

This happens because WaitForLockersMultiple() does not take prepared xacts into account. Meanwhile CREATE INDEX CONCURRENTLY expects that locks are dropped only when transaction commit is visible.

This issue affects pg_repack and similar machinery based on CIC.

PFA draft of a fix.

Best regards, Andrey Borodin.

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Improve contrib/amcheck's tests for CREATE INDEX CONCURRENTLY.

  2. Fix minor memory leaks in pg_dump.

  3. Avoid race in RelationBuildDesc() affecting CREATE INDEX CONCURRENTLY.

  4. Fix CREATE INDEX CONCURRENTLY for the newest prepared transactions.

  5. Add -w back to the flags for pg_ctl (re)start in PostgresNode

  6. Fix CREATE INDEX CONCURRENTLY for simultaneous prepared transactions.