Horton

Re: Reduce TupleHashEntryData struct size by half

Alvaro Herrera <alvherre@alvh.no-ip.org>

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From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: David Rowley <dgrowleyml@gmail.com>
Cc: Jeff Davis <pgsql@j-davis.com>, Heikki Linnakangas <hlinnaka@iki.fi>, pgsql-hackers@postgresql.org
Date: 2025-01-14T18:11:21Z
Lists: pgsql-hackers 
On 2025-Jan-14, David Rowley wrote:

> The trick would be to ensure ExecClearTuple() still works. You
> obviously don't want to try and pfree() something that isn't a pointer
> to a palloc'd chunk. I'm not sure what the best API is, but I do see
> there are other places that might benefit from something that allows
> this.  The two usages of ExecCopySlotMinimalTuple() in nodeMemoize.c
> are candidates.

Maybe it would work to set a new flag in TupleTableSlot->tts_flag so
that ExecClearTuple() knows to handle it in some particular way (i.e.,
just skip the ->clear call altogether), with the idea that the tuple
memory belongs elsewhere and must not be freed by ExecClearTuple?

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"Los dioses no protegen a los insensatos.  Éstos reciben protección de
otros insensatos mejor dotados" (Luis Wu, Mundo Anillo)

Commits

  1. Comment fixups from 626df47ad9.

  2. Remove 'additional' pointer from TupleHashEntryData.

  3. Add ExecCopySlotMinimalTupleExtra().

  4. Create accessor functions for TupleHashEntry.

  5. TupleHashTable: store additional data along with tuple.

  6. ExecInitAgg: update aggstate->numaggs and ->numtrans earlier.

  7. nodeSetOp.c: missing additionalsize for BuildTupleHashTable().

  8. Remove unused TupleHashTableData->entrysize.

  9. Add missing typedefs.list entry for AggStatePerGroupData.