On 2020-Jul-28, Peter Geoghegan wrote:
> On Mon, Jul 27, 2020 at 10:25 AM Alvaro Herrera
> <alvherre@2ndquadrant.com> wrote:
> > (I was also considering whether it needs to be a loop to reobtain root
> > tuples, in case a concurrent transaction can create a new item while
> > we're checking that item; but I don't think that can really happen for
> > one individual tuple.)
>
> I wonder if something like that is the underlying problem in a recent
> problem case involving a "REINDEX index
> pg_class_tblspc_relfilenode_index" command that runs concurrently with
> the regression tests:
>
> https://postgr.es/m/CAH2-WzmBxu4o=pMsniur+bwHqCGCmV_AOLkuK6BuU7ngA6evqw@mail.gmail.com
>
> We see a violation of the HOT invariant in this case, though only for
> a system catalog index, and only in fairly particular circumstances
> involving concurrency.
Hmm. As far as I understand, the bug Anastasia reports can only hit an
index build that occurs concurrently to heap updates; and that cannot
happen for a regular index build, only for CREATE INDEX CONCURRENTLY and
REINDEX CONCURRENTLY. So unless I miss something, it's not related to
that other bug.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
