Andres Freund wrote:
> On 2014-04-22 18:01:40 -0300, Alvaro Herrera wrote:
> > Thanks for the analysis and patches. I've been playing with this on my
> > own a bit, and one thing that I just noticed is that at least for
> > heap_update I cannot reproduce a problem when the xmax is originally a
> > multixact, so AFAICT the number of places that need patched aren't as
> > many.
>
> I am quite uncomfortable with that assumption. I don't immediately see a
> problem for some of the cases, but leaving them in a weaker state than
> 9.2 makes me uncomfortable.
That's true too.
I'm thinking about the comparison of full infomask as you propose
instead of just the bits that we actually care about. I think the only
thing that could cause a spurious failure (causing an extra execution of
the HeapTupleSatisfiesUpdate call and the stuff below) is somebody
setting HEAP_XMIN_COMMITTED concurrently; but that seems infrequent
enough that it should pretty harmless. However, should we worry about
possible future infomask bit changes that could negatively affect this
behavior?
--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
