Re: BitmapHeapScan streaming read user and prelim refactoring

On Mon, Apr 22, 2024 at 1:01 PM Melanie Plageman
<melanieplageman(at)gmail(dot)com> wrote:
>
> On Thu, Apr 18, 2024 at 5:39 AM Tomas Vondra
> <tomas(dot)vondra(at)enterprisedb(dot)com> wrote:
> >
> > On 4/18/24 09:10, Michael Paquier wrote:
> > > On Sun, Apr 07, 2024 at 10:54:56AM -0400, Melanie Plageman wrote:
> > >> I've added an open item [1], because what's one open item when you can
> > >> have two? (me)
> > >
> > > And this is still an open item as of today. What's the plan to move
> > > forward here?
> >
> > AFAIK the plan is to replace the asserts with actually resetting the
> > rs_empty_tuples_pending field to 0, as suggested by Melanie a week ago.
> > I assume she was busy with the post-freeze AM reworks last week, so this
> > was on a back burner.
>
> yep, sorry. Also I took a few days off. I'm just catching up today. I
> want to pop in one of Richard or Tomas' examples as a test, since it
> seems like it would add some coverage. I will have a patch soon.

The patch with a fix is attached. I put the test in
src/test/regress/sql/join.sql. It isn't the perfect location because
it is testing something exercisable with a join but not directly
related to the fact that it is a join. I also considered
src/test/regress/sql/select.sql, but it also isn't directly related to
the query being a SELECT query. If there is a better place for a test
of a bitmap heap scan edge case, let me know.

One other note: there is some concurrency effect in the parallel
schedule group containing "join" where you won't trip the assert if
all the tests in that group in the parallel schedule are run. But, if
you would like to verify that the test exercises the correct code,
just reduce the group containing "join".

- Melanie