Re: Reduce TupleHashEntryData struct size by half

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