Re: Adding a test for speculative insert abort case

On Thu, May 16, 2019 at 2:03 PM Andres Freund <andres(at)anarazel(dot)de> wrote:

> Hi,
>
> On 2019-05-16 13:59:47 -0700, Melanie Plageman wrote:
> > On Wed, May 15, 2019 at 10:32 PM Ashwin Agrawal <aagrawal(at)pivotal(dot)io>
> wrote:
> >
> > >
> > > The second index would help to hold the session after inserting the
> tuple
> > > in unique index but before completing the speculative insert. Hence,
> helps
> > > to create the condition easily. I believe order of index insertion is
> > > helping here that unique index is inserted and then non-unique index is
> > > inserted too.
> > >
> > >
> > Oh, cool. I didn't know that execution order would be guaranteed for
> which
> > index
> > to insert into first.
>
> It's not *strictly* speaking *always* well defined. The list of indexes
> is sorted by the oid of the index - so once created, it's
> consistent. But when the oid assignment wraps around, it'd be the other
> way around. But I think it's ok to disregard that - it'll never happen
> in regression tests run against a new cluster, and you'd have to run
> tests against an installed cluster for a *LONG* time for a *tiny* window
> where the wraparound would happen precisely between the creation of the
> two indexes.
>
> Makes sense?
>

Yep, thanks.

> I guess we could make that case a tiny bit easier to diagnose in the
> extremely unlikely case it happens by having a step that outputs
> SELECT 'index_a'::regclass::int8 < 'index_b'::regclass::int8;
>
>
Good idea.
I squashed the changes I suggested in previous emails, Ashwin's patch, my
suggested updates to that patch, and the index order check all into one
updated
patch attached.

--
Melanie Plageman