Re: Multi-xacts and our process problem

On 05/12/2015 12:00 AM, Bruce Momjian wrote:
> Multi-xacts were made durable in Postgres 9.3 (released 2013-09-09) to
> allow primary-key-column-only locks. 1.7 years later, we are still
> dealing with bugs related to this feature. Obviously, something is
> wrong.
>
> There were many 9.3 minor releases containing multi-xacts fixes, and
> these fixes have extended into 9.4. After the first few bug-fix
> releases, I questioned whether we needed to revert or rework the
> feature, but got no positive response. Only in the past few weeks have
> we got additional people involved.

The "revert or rework" ship had already sailed at that point. I don't
think we had much choice than just soldier through the bugs after the
release.

> I think we now know that our inaction didn't serve us well. The
> question is how can we identify chronic problems and get resources
> involved sooner. I feel we have been "asleep at the wheel" to some
> extent on this.

Yeah. I think the problem was that no-one realized that this was a
significant change to the on-disk format. It was deceptively
backwards-compatible. When it comes to permanent on-disk structures, we
should all be more vigilant in the review.

- Heikki