Re: pgsql: Make heap TID a tiebreaker nbtree index column.

On Wed, Mar 20, 2019 at 11:08 AM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> The diffs all are related to the order of operations in a DROP OWNED BY
> command, so I think blaming SELinux is just blaming the messenger.
> This comes down to the point that we didn't do anything to ensure
> drop order stability in shdepend-driven drops. Maybe we need to be
> honest about that.

You can certainly make that argument. However, we still wouldn't make
broad guarantees about test stability that ensure that this general
category of flappiness goes away forever (IIRC the role stuff still
has the odd problem). I suppose that you could scope the guarantees as
being about pg_depend and pg_shdepend, but that seems arbitrary to me.

Your work on test stability probably eliminated 98% of the problems.
It's still early, but the buildfarm is mostly fine.

> Or do you have reason to think that your changes
> will result in stability in that drop order anyway? If so, why?

I strongly suspect that my changes will leave the output about as
stable as before, or will slightly improve matters. Duplicates are now
in ascending order, as opposed to very close to descending order. I
think that it would be fine to rely on the new output ordering, even
though it theoretically isn't any more stable.

--
Peter Geoghegan