From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
Cc: | Andres Freund <andres(at)anarazel(dot)de>, Manuel Rigger <rigger(dot)manuel(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org> |
Subject: | Re: ERROR: found unexpected null value in index |
Date: | 2019-07-11 23:01:14 |
Message-ID: | 23597.1562886074@sss.pgh.pa.us |
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Lists: | pgsql-bugs |
Peter Geoghegan <pg(at)bowt(dot)ie> writes:
> On Thu, Jul 11, 2019 at 2:20 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> As far as I can tell, no special finagling is needed: if we just use
>> the regular index-only-scan logic then this all works the way we want,
>> and it's actually better than before because we get to skip heap visits
>> altogether when dealing with unchanging data. Attached is a patch
>> against HEAD that seems to do all the right things.
> Interesting approach. I certainly prefer it to the alternative
> approach of framing the problem as a visibility concern.
Yes, I certainly like this better than my previous attempt.
I still feel like we're going to want to push (most of?) this logic
below the tableam API at some point, because its implementation was
and remains tied to heap+btree. But other table AMs are likely to
support ordered scan accesses of some sort, and they're going to
want to be able to adjust the planner's extremal-value estimates
too. It's a job for later though.
regards, tom lane
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