Horton

Re: Parallel Append subplan order instability on aye-aye

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: David Rowley <david.rowley@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2019-05-22T04:44:35Z
Lists: pgsql-hackers 
Thomas Munro <thomas.munro@gmail.com> writes:
> Huh, idiacanthus failed showing vacuum_count 0, in select_parallel.
> So ... the VACUUM command somehow skipped those tables?

No, because the reltuples counts are correct.  I think what we're
looking at there is the stats collector dropping a packet that
told it about vacuum activity.

I'm surprised that we saw such a failure so quickly.  I'd always
figured that the collector mechanism, while it's designed to be
unreliable, is only a little bit unreliable.  Maybe it's more
than a little bit.

			regards, tom lane

Commits

  1. ANALYZE a_star and its children to avoid plan instability in tests.

  2. Finish reverting "Insert temporary debugging output in regression tests."

  3. Partially revert "Insert temporary debugging output in regression tests."

  4. Insert temporary debugging output in regression tests.

  5. Improve the heuristic for ordering child paths of a parallel append.