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help / color / mirror / Atom feedFrom: Tom Lane <[email protected]>
To: Smolkin Grigory <[email protected]>
Cc: [email protected]
Subject: Re: race condition in pg_class
Date: Wed, 25 Oct 2023 14:06:45 -0400
Message-ID: <[email protected]> (raw)
In-Reply-To: <CAMp+ueZQz3yDk7qg42hk6-9gxniYbp-=bG2mgqecErqR5gGGOA@mail.gmail.com>
References: <CAMp+ueZQz3yDk7qg42hk6-9gxniYbp-=bG2mgqecErqR5gGGOA@mail.gmail.com>
Smolkin Grigory <[email protected]> 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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