Re: BUG #14210: filter by "=" constraint doesn't work when hash index is present on a column

On Mon, Jun 27, 2016 at 1:22 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Peter Geoghegan <pg(at)heroku(dot)com> writes:
>> I like this idea. Should I write a patch?
>
> BTW, while you're at it: it strikes me that the threshold should be
> either min(NBuffers, maintenance_work_mem) or
> min(NLocBuffer, maintenance_work_mem), depending on whether we're
> talking about a regular or temp table/index. That is, there's a
> pre-existing bug here that when NLocBuffer is a good deal less than
> NBuffers (which is the typical case nowadays) you'll get a lot of
> thrashing between local buffers and kernel cache, if the index isn't
> quite big enough to trigger the sorting code. This might not manifest
> as actual I/O, but it's not the intended behavior either.

Understood. It's on my TODO list for the week, although I'll
prioritize isolating and fixing that UPSERT "attempted to delete
invisible tuple" bug.

--
Peter Geoghegan