Re: race condition in pg_class

> 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?

No chance. Our infrastructure dont do that, and users dont just have the
privileges to mess with pg_catalog.

ср, 25 окт. 2023 г. в 21:06, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>:

> 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
>