Horton

Re: Default setting for enable_hashagg_disk

Bruce Momjian <bruce@momjian.us>

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From: Bruce Momjian <bruce@momjian.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Andres Freund <andres@anarazel.de>, Robert Haas <robertmhaas@gmail.com>, David Rowley <dgrowleyml@gmail.com>, Jeff Davis <pgsql@j-davis.com>, Justin Pryzby <pryzby@telsasoft.com>, Melanie Plageman <melanieplageman@gmail.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2020-06-24T23:15:17Z
Lists: pgsql-hackers, pgsql-docs 
On Wed, Jun 24, 2020 at 11:02:10PM +0200, Tomas Vondra wrote:
> > Indeed. And then perhaps we could eventually add some reporting /
> > monitoring infrastructure for the cases where plan time and execution
> > time memory estimate/usage widely differs.
> > 
> 
> I wouldn't mind something like that in general - not just for hashagg,
> but for various other nodes.

Well, other than worrying about problems with pre-13 queries, how is
this different from any other spill to disk when we exceed work_mem,
like sorts for merge join.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EnterpriseDB                             https://enterprisedb.com

  The usefulness of a cup is in its emptiness, Bruce Lee

Commits

  1. Add hash_mem_multiplier GUC.

  2. HashAgg: use better cardinality estimate for recursive spilling.

  3. Remove hashagg_avoid_disk_plan GUC.

  4. Doc fixup for hashagg_avoid_disk_plan GUC.

  5. Rework HashAgg GUCs.

  6. Disk-based Hash Aggregation.

  7. Implement partition-wise grouping/aggregation.

  8. Defer creation of partially-grouped relation until it's needed.