Re: generic plans and "initial" pruning

On Wed, Feb 8, 2023 at 7:31 PM Amit Langote <amitlangote09(at)gmail(dot)com> wrote:
> On Tue, Feb 7, 2023 at 23:38 Andres Freund <andres(at)anarazel(dot)de> wrote:
>> The tests seem to frequently hang on freebsd:
>> https://cirrus-ci.com/github/postgresql-cfbot/postgresql/commitfest%2F42%2F3478
>
> Thanks for the heads up. I’ve noticed this one too, though couldn’t find the testrun artifacts like I could get for some other failures (on other cirrus machines). Has anyone else been a similar situation?

I think I have figured out what might be going wrong on that cfbot
animal after building with the same CPPFLAGS as that animal locally.
I had forgotten to update _out/_readRangeTblEntry() to account for the
patch's change that a view's RTE_SUBQUERY now also preserves relkind
in addition to relid and rellockmode for the locking consideration.

Also, I noticed that a multi-query Portal execution with rules was
failing (thanks to a regression test added in a7d71c41db) because of
the snapshot used for the 2nd query onward not being updated for
command ID change under patched model of multi-query Portal execution.
To wit, under the patched model, all queries in the multi-query Portal
case undergo ExecutorStart() before any of it is run with
ExecutorRun(). The patch hadn't changed things however to update the
snapshot's command ID for the 2nd query onwards, which caused the
aforementioned test case to fail.

This new model does however mean that the 2nd query onwards must use
PushCopiedSnapshot() given the current requirement of
UpdateActiveSnapshotCommandId() that the snapshot passed to it must
not be referenced anywhere else. The new model basically requires
that each query's QueryDesc points to its own copy of the
ActiveSnapshot. That may not be a thing in favor of the patched model
though. For now, I haven't been able to come up with a better
alternative.

--
Thanks, Amit Langote
EDB: http://www.enterprisedb.com