Re: reindex concurrently and two toast indexes

From: Julien Rouhaud <rjuju123(at)gmail(dot)com>
To: Michael Paquier <michael(at)paquier(dot)xyz>
Cc: Justin Pryzby <pryzby(at)telsasoft(dot)com>, Sergei Kornilov <sk(at)zsrv(dot)org>, Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com>, Michael Paquier <michael(dot)paquier(at)gmail(dot)com>, Andreas Karlsson <andreas(at)proxel(dot)se>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: reindex concurrently and two toast indexes
Date: 2020-02-22 07:09:24
Message-ID: 20200222070924.GA57285@nol
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On Tue, Feb 18, 2020 at 07:39:49AM +0100, Julien Rouhaud wrote:
> On Tue, Feb 18, 2020 at 7:19 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> >
> > On Tue, Feb 18, 2020 at 07:06:25AM +0100, Julien Rouhaud wrote:
> > > On Tue, Feb 18, 2020 at 6:30 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> > >> Hmm. There could be an argument here for skipping invalid toast
> > >> indexes within reindex_index(), because we are sure about having at
> > >> least one valid toast index at anytime, and these are not concerned
> > >> with CIC.
> > >
> > > Or even automatically drop any invalid index on toast relation in
> > > reindex_relation, since those can't be due to a failed CIC?
> >
> > No, I don't like much outsmarting REINDEX with more index drops than
> > it needs to do. And this would not take care of the case with REINDEX
> > INDEX done directly on a toast index.
> Well, we could still do both but I get the objection. Then skipping
> invalid toast indexes in reindex_relation looks like the best fix.

PFA a patch to fix the problem using this approach.

I also added isolation tester regression tests. The failure is simulated using
a pg_cancel_backend() on top of pg_stat_activity, using filters on a
specifically set application name and the query text to avoid any unwanted
interaction. I also added a 1s locking delay, to ensure that even slow/CCA
machines can consistently reproduce the failure. Maybe that's not enough, or
maybe testing this scenario is not worth the extra time.

Attachment Content-Type Size
0001-Don-t-reindex-invalid-indexes-on-TOAST-tables-v1.patch text/plain 6.3 KB

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