Re: old_snapshot_threshold's interaction with hash index

On Mon, May 2, 2016 at 04:02:35PM -0500, Kevin Grittner wrote:
> On Sun, May 1, 2016 at 1:43 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> > On Sun, May 1, 2016 at 12:05 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> >>
> >> Currently we do the test for old snapshot (TestForOldSnapshot) for hash
> >> indexes while scanning them. Does this test makes any sense for hash
> >> indexes considering LSN on hash index will always be zero (as hash indexes
> >> are not WAL-logged)? It seems to me that PageLSN check in
> >> TestForOldSnapshot() will always return false which means that the error
> >> "snapshot too old" won't be generated for hash indexes.
> >>
> >> Am I missing something here, if not, then I think we need a way to
> >> prohibit pruning for hash indexes based on old_snapshot_threshold?
> >
> > What I mean to say here is prohibit pruning the relation which has hash
> > index based on old_snapshot_threshold.
>
> Good spot; added to the open issues page.

Uh, I have no idea how this would be fixed if the PageLSN is zero. Do
you?

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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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