Horton

Re: Default setting for enable_hashagg_disk

Justin Pryzby <pryzby@telsasoft.com>

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From: Justin Pryzby <pryzby@telsasoft.com>
To: Jeff Davis <pgsql@j-davis.com>
Cc: Melanie Plageman <melanieplageman@gmail.com>, Robert Haas <robertmhaas@gmail.com>, Tomas Vondra <tomas.vondra@2ndquadrant.com>, pgsql-hackers@postgresql.org
Date: 2020-06-12T02:45:43Z
Lists: pgsql-hackers, pgsql-docs 
On Thu, Jun 11, 2020 at 01:22:57PM -0700, Jeff Davis wrote:
> On Wed, 2020-06-10 at 11:39 -0700, Jeff Davis wrote:
> > 1. Testing the spilling of hashed grouping sets: I'm inclined to just
> > get rid of enable_groupingsets_hash_disk and use Melanie's stats-
> > hacking approach instead.
> 
> Fixed in 92c58fd9.
> 
> > think the names you suggested quite fit, but the idea to use a more
> > interesting GUC value might help express the behavior. Perhaps making
> > enable_hashagg a ternary "enable_hashagg=on|off|avoid_disk"? The word
> > "reject" is too definite for the planner, which is working with
> > imperfect information.
> 
> I renamed enable_hashagg_disk to hashagg_avoid_disk_plan, which I think
> satisfies the concerns raised here. Also in 92c58fd9.

Thanks for considering :)

I saw you updated the Open Items page, but put the items into "Older Bugs /
Fixed".

I moved them underneath "Resolved" since they're all new in v13.
https://wiki.postgresql.org/index.php?title=PostgreSQL_13_Open_Items&diff=34995&oldid=34994

-- 
Justin

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.