Re: assertion failure 9.3.4

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.

> For now I offer a cleaned up version of your patch to add the assertion
> that multis don't contain multiple updates.  I considered the idea of
> making this #ifdef USE_ASSERT_CHECKING, because it has to walk the
> complete array of members; and then have full elogs in MultiXactIdExpand
> and MultiXactIdCreate, which are lighter because they can check more
> easily.  But on second thoughts I refrained from doing that, because
> surely the arrays are not as large anyway, are they.

Yea, I think it's fine to do it where it's in the proposed patch.

> I think I should push this patch first, so that Andrew and Josh can try
> their respective test cases which should start throwing errors, then
> push the actual fixes.  Does that sound okay?

+1

Greetings,

Andres Freund

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