Horton

Re: Default setting for enable_hashagg_disk

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Jeff Davis <pgsql@j-davis.com>, David Rowley <dgrowleyml@gmail.com>, Stephen Frost <sfrost@snowman.net>, Tom Lane <tgl@sss.pgh.pa.us>, Andres Freund <andres@anarazel.de>, Bruce Momjian <bruce@momjian.us>, Robert Haas <robertmhaas@gmail.com>, Justin Pryzby <pryzby@telsasoft.com>, Melanie Plageman <melanieplageman@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2020-07-27T18:30:39Z
Lists: pgsql-hackers, pgsql-docs

Attachments

On Mon, Jul 27, 2020 at 11:24 AM Alvaro Herrera
<alvherre@2ndquadrant.com> wrote:
> > Are you proposing that I just put the prototype in miscadmin.h, while
> > leaving the implementation where it is (in nodeHash.c)?
>
> Yes, that's in the part of my reply you didn't quote:
>
> : It remains strange to have the function in executor
> : implementation, but I don't offhand see a better place, so maybe it's
> : okay where it is.

Got it.

I tried putting the prototype in miscadmin.h, and I now agree that
that's the best way to do it -- that's how I do it in the attached
revision. No other changes.

The v4-0001-Remove-hashagg_avoid_disk_plan-GUC.patch changes are
surprisingly complicated. It would be nice if you could take a look at
that aspect (or confirm that it's included in your review).

-- 
Peter Geoghegan

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.