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.kapila16@gmail.com> wrote:
> > On Sun, May 1, 2016 at 12:05 PM, Amit Kapila <amit.kapila16@gmail.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?

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com

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