Re: Connections hang indefinitely while taking a gin index's LWLock buffer_content lock

On Thu, 21 Mar 2019 at 15:18, Alexander Korotkov <aekorotkov(at)gmail(dot)com>
wrote:

> On Thu, Mar 21, 2019 at 9:26 PM Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>
>

> > It's been pointed out to me that 52ac6cd2d0cd70e01291e0ac4ee6d068b69bc478
> > introduced a WAL incompatibility that has not been flagged.
> >
> > In ginRedoDeletePage() we use the struct directly to read the WAL
> record, so if a WAL record was written prior to
> 52ac6cd2d0cd70e01291e0ac4ee6d068b69bc478, yet read by code at
> 52ac6cd2d0cd70e01291e0ac4ee6d068b69bc478 or later then we will have
> problems, since deleteXid will not be set correctly.
> >
> > It seems this should not have been backpatched.
> >
> > Please give your assessment.
>
> Oh, right. This is my fault.
>
> However, I think this still can be backpatched correctly. We can
> determine whether xlog record data contains deleteXid by its size.
> See the attached patch. I haven't test this yet. I'm going to test
> it. If OK, then push.
>

Patch looks like it will work.

I'd prefer to see a tighter test, since the length should either be the old
or new length, no other.

Thanks

--
Simon Riggs http://www.2ndQuadrant.com/
<http://www.2ndquadrant.com/>
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