From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
---|---|
To: | Smolkin Grigory <smallkeen(at)gmail(dot)com> |
Cc: | pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: race condition in pg_class |
Date: | 2023-10-25 18:06:45 |
Message-ID: | 1006408.1698257205@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Smolkin Grigory <smallkeen(at)gmail(dot)com> writes:
> We are running PG13.10 and recently we have encountered what appears to be
> a bug due to some race condition between ALTER TABLE ... ADD CONSTRAINT and
> some other catalog-writer, possibly ANALYZE.
> The problem is that after successfully creating index on relation (which
> previosly didnt have any indexes), its pg_class.relhasindex remains set to
> "false", which is illegal, I think.
> Index was built using the following statement:
> ALTER TABLE "example" ADD constraint "example_pkey" PRIMARY KEY (id);
ALTER TABLE ADD CONSTRAINT would certainly have taken
AccessExclusiveLock on the "example" table, which should be sufficient
to prevent anything else from touching its pg_class row. The only
mechanism I can think of that might bypass that is a manual UPDATE on
pg_class, which would just manipulate the row as a row without concern
for associated relation-level locks. Any chance that somebody was
doing something like that?
regards, tom lane
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