Re: Performance degradation on concurrent COPY into a single relation in PG16.

Hi,

On 2023-10-13 11:30:35 -0700, Andres Freund wrote:
> On 2023-10-13 10:39:10 -0700, Andres Freund wrote:
> > On 2023-10-12 09:24:19 -0700, Andres Freund wrote:
> > > I kind of had hoped somebody would comment on the approach.  Given that nobody
> > > has, I'll push the minimal fix of resetting the state in
> > > ReleaseBulkInsertStatePin(), even though I think architecturally that's not
> > > great.
> > 
> > I spent some time working on a test that shows the problem more cheaply than
> > the case upthread. I think it'd be desirable to have a test that's likely to
> > catch an issue like this fairly quickly. We've had other problems in this
> > realm before - there's only a single test that fails if I remove the
> > ReleaseBulkInsertStatePin() call, and I don't think that's guaranteed at all.
> > 
> > I'm a bit on the fence on how large to make the relation. For me the bug
> > triggers when filling both relations up to the 3rd block, but how many rows
> > that takes is somewhat dependent on space utilization on the page and stuff.
> > 
> > Right now the test uses data/desc.data and ends up with 328kB and 312kB in two
> > partitions. Alternatively I could make the test create a new file to load with
> > copy that has fewer rows than data/desc.data - I didn't see another data file
> > that works conveniently and has fewer rows.  The copy is reasonably fast, even
> > under something as expensive as rr (~60ms). So I'm inclined to just go with
> > that?
> 
> Patch with fix and test attached (0001).

Pushed that.

Greetings,

Andres