Re: PG15 beta1 sort performance regression due to Generation context change

David Rowley <dgrowleyml@gmail.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