Horton

Re: Add contrib/pg_logicalsnapinspect

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Masahiko Sawada <sawada.mshk@gmail.com>
Cc: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>, Andres Freund <andres@anarazel.de>, Peter Smith <smithpb2250@gmail.com>, Peter Eisentraut <peter@eisentraut.org>, shveta malik <shveta.malik@gmail.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, pgsql-hackers@lists.postgresql.org
Date: 2025-03-07T04:56:23Z
Lists: pgsql-hackers

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  1. Fix indentation issue

  2. pg_logicalinspect: Stabilize isolation tests.

  3. Add contrib/pg_logicalinspect.

  4. Move SnapBuild and SnapBuildOnDisk structs to snapshot_internal.h.

On Fri, Mar 7, 2025 at 3:19 AM Masahiko Sawada <sawada.mshk@gmail.com> wrote:
>
> On Wed, Mar 5, 2025 at 4:05 AM Bertrand Drouvot
> <bertranddrouvot.pg@gmail.com> wrote:
> >
> > Hi,
> >
> > On Wed, Mar 05, 2025 at 02:42:15PM +0530, Amit Kapila wrote:
> > > On Wed, Mar 5, 2025 at 12:47 PM Bertrand Drouvot
> > > <bertranddrouvot.pg@gmail.com> wrote:
> > > >
> > > > Agree, PFA a patch doing so.
> > > >
> > >
> > > It would be better if you could add a few comments atop the
> > > permutation line to explain the working of the test.
> >
> > yeah makes sense. Done in the attached, and bonus point I realized that the
> > test could be simplified (so, removing useless steps in passing).
> >
>
> Thank you for the patch.
>
> The new simplified test case can be pretty-formatted as:
>
> init
> begin
> savepoint
> truncate
>                 checkpoint-1
>                 get_changes-1
> commit
>                 checkpoint-2
>                 get_changes-2
>                 info_catchange check
>                 info_committed check
>                 meta check
>
> IIUC if another checkpoint happens between get_change-2 and the
> subsequent checks, the first snapshot would be removed during the
> checkpoint, resulting in a test failure. I think we could check the
> snapshot files while one transaction keeps open. The more simplified
> test case would be:
>
> init
> begin
> savepoint
> insert(cat-change)
>                 begin
>                 insert(cat-change)
>                 commit
>                 checkpoint
>                 get_changes
>                 info_catchange check
>                 info_committed check
>                 meta check
> commit
>
> In this test case, we would have at least one serialized snapshot that
> has both cat-changes and committed txns. What do you think?
>

Your proposed change in the test sounds better than what we have now
but I think we should also avoid autovacuum to perform analyze as that
may add additional counts. For test_decoding, we keep
autovacuum_naptime = 1d in logical.conf file, we can either use the
same here or simply keep autovacuum off.

-- 
With Regards,
Amit Kapila.