Re: Fix slot's xmin advancement and subxact's lost snapshots in decoding.

On 2018-Jun-11, Antonin Houska wrote:

> Arseny Sher <a(dot)sher(at)postgrespro(dot)ru> wrote:
> > Please see detailed description of the issues, tests which reproduce
> > them and fixes in the attached patch.
>
> I've played with your tests and gdb for a while, both w/o and with your
> patch. I think I can understand both problems. I could not invent simpler way
> to fix them.
>
> One comment about the coding: since you introduce a new transaction list and
> it's sorted by LSN, I think you should make the function AssertTXNLsnOrder()
> more generic and use it to check the by_base_snapshot_lsn list too. For
> example call it after the list insertion and deletion in
> ReorderBufferPassBaseSnapshot().

I've been going over this patch also, and I've made a few minor edits of
the patch and the existing code as I come to understand what it's all
about.

> Also I think it makes no harm if you split the diff into two, although both
> fixes use the by_base_snapshot_lsn field.

Please don't.

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Álvaro Herrera https://www.2ndQuadrant.com/
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