Horton

Re: BUG #17949: Adding an index introduces serialisation anomalies.

Dmitry Dolgov <9erthalion6@gmail.com>

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From: Dmitry Dolgov <9erthalion6@gmail.com>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: artem.anisimov.255@gmail.com, pgsql-bugs@lists.postgresql.org
Date: 2023-06-21T08:58:12Z
Lists: pgsql-bugs 
> On Tue, Jun 20, 2023 at 01:22:19PM +1200, Thomas Munro wrote:
> On Tue, Jun 20, 2023 at 12:18 AM Dmitry Dolgov <9erthalion6@gmail.com> wrote:
> > > On Mon, Jun 19, 2023 at 09:30:12PM +1200, Thomas Munro wrote:
> > > +#if 0
> > >         /*
> > >          * Ignore any claimed entries past what we think is the end of the
> > >          * relation. It may have been extended after the start of our scan (we
> > >          * only hold an AccessShareLock, and it could be inserts from this
> > >          * backend).
> > >          */
> > >         if (block >= hscan->rs_nblocks)
> > >                 return false;
> > > +#endif
> >
> > Great, thanks! Can confirm, after applying both the posted patch and the
> > change above the issue is not reproducible anymore.
>
> Here's a cleaned-up version of the first two changes.  What do you
> think about the assertions I make in the commit message for 0002?

Yep, it sounds correct to me. After a quick look I couldn't find where
exactly the similar code lives in the pre-tableam version, so can't say
anything about back-patching there.

Commits

  1. Fix race in SSI interaction with bitmap heap scan.

  2. Fix race in SSI interaction with gin fast path.

  3. Fix race in SSI interaction with empty btrees.

  4. Re-think predicate locking on GIN indexes.