Horton

Re: Default setting for enable_hashagg_disk

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Jeff Davis <pgsql@j-davis.com>, "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Date: 2020-04-09T19:26:36Z
Lists: pgsql-hackers, pgsql-docs 
On Thu, Apr 9, 2020 at 7:49 AM Tomas Vondra
<tomas.vondra@2ndquadrant.com> wrote:
> It it really any different from our enable_* GUCs? Even if you do e.g.
> enable_sort=off, we may still do a sort. Same for enable_groupagg etc.

I think it's actually pretty different. All of the other enable_* GUCs
disable an entire type of plan node, except for cases where that would
otherwise result in planning failure. This just disables a portion of
the planning logic for a certain kind of node, without actually
disabling the whole node type. I'm not sure that's a bad idea, but it
definitely seems to be inconsistent with what we've done in the past.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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.