Re: Re: [COMMITTERS] pgsql: Avoid extra locks in GetSnapshotData if old_snapshot_threshold < - Mailing list pgsql-hackers

Kevin Grittner <kgrittn@gmail.com> writes:
> On Tue, May 24, 2016 at 12:00 PM, Andres Freund <andres@anarazel.de> wrote:
>> Analyze IIRC acquires a new snapshot when getting sample rows,

> I could not find anything like that, and a case-insensitive search
> of analyze.c finds no occurrences of "snap".  Can you remember
> where you think you saw something that would cause the ANALYZE
> command in my test to use a snapshot other than the one from the
> REPEATABLE READ transaction in which it was run?

The control logic concerned with that is in vacuum.c, not analyze.c.
AFAICS a manual ANALYZE that's within a transaction block would use
the prevailing snapshot (see in_outer_xact tests).  There are a lot
of cases that wouldn't, though.

            regards, tom lane