Re: Reduce TupleHashEntryData struct size by half - Mailing list pgsql-hackers

From Jeff Davis
Subject Re: Reduce TupleHashEntryData struct size by half
Date
Msg-id 6f61828ad7381fc03492cef267f896e99d38ead4.camel@j-davis.com
Whole thread Raw
In response to Re: Reduce TupleHashEntryData struct size by half  (David Rowley <dgrowleyml@gmail.com>)
Responses Re: Reduce TupleHashEntryData struct size by half
List pgsql-hackers
On Sun, 2025-01-12 at 14:54 +1300, David Rowley wrote:
> While I do understand the desire to reduce Hash Agg's memory usage,
> has this really been through enough performance testing to be getting
> committed?

Perhaps not. I'm going to revert it while we sort it out, and hopefully
we can find a solution because it's a substantial memory savings.


> I wonder if there's some other better way of doing this. Would it be
> worth having some function like ExecCopySlotMinimalTuple() that
> accepts an additional parameter so that the palloc allocates N more
> bytes at the end?  Maybe it's worth hunting around to see if there's
> any other executor nodes that could benefit from that infrastructure.

That would be convenient, but doesn't seem like a great separation of
responsibilities. Perhaps some API that separated the length
calculation, and accepted a caller-supplied buffer?

Regards,
    Jeff Davis





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