Re: BUG #15830: index pg_stat_all_indexes.idx_tup_read statistic error?

From: Peter Geoghegan <pg(at)bowt(dot)ie>
To: digoal(at)126(dot)com, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org>
Subject: Re: BUG #15830: index pg_stat_all_indexes.idx_tup_read statistic error?
Date: 2019-06-01 12:21:39
Message-ID: CAH2-WzkKNOO6YqOVvh80rt-4ZuU_pHZ1XitOeMn212jVQXyqvA@mail.gmail.com
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On Sat, Jun 1, 2019 at 12:01 AM PG Bug reporting form
<noreply(at)postgresql(dot)org> wrote:
> The question is, does INDEX SCAN clean up the garbage version of leaf page?
> Or it's a bug?

Yes, sometimes that happens -- the kill_prior_tuple optimization can
kick in, even with a simple SELECT.

It would be clearer what was going on if you forced a bitmap index
scan (e.g. "set enable_indexscan=off;"). That way, the EXPLAIN
(ANALYZE, BUFFERS) instrumentation will show heap blocks and index
blocks separately.

--
Peter Geoghegan

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