| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | David Rowley <dgrowleyml(at)gmail(dot)com> |
| Cc: | Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: PG15 beta1 sort performance regression due to Generation context change |
| Date: | 2022-05-23 22:04:15 |
| Message-ID: | 1347835.1653343455@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> GenerationRealloc: uses "size" to figure out if the new size is
> smaller than the old size. Maybe we could just always move to a new
> chunk regardless of if the new size is smaller or larger than the old
> size.
I had the same idea ... but we need to know the old size to know how much
to copy.
> GenerationGetChunkSpace: Uses "size" to figure out the amount of
> memory is used by the chunk. I'm not sure how we'd work around the
> fact that USEMEM() uses that extensively in tuplesort.c to figure out
> how much memory we're using.
Ugh, that seems like a killer.
regards, tom lane
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