| From: | David Rowley <david(dot)rowley(at)2ndquadrant(dot)com> |
|---|---|
| To: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
| Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Andrew Gierth <andrew(at)tao11(dot)riddles(dot)org(dot)uk>, Bartosz Polnik <bartoszpolnik(at)gmail(dot)com>, PostgreSQL mailing lists <pgsql-bugs(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: BUG #15577: Query returns different results when executed multiple times |
| Date: | 2019-01-10 00:32:30 |
| Message-ID: | CAKJS1f9f4UFfzO9VuyO99Rehf1h7Aeco-+9q4rL0e6j8_O38Xg@mail.gmail.com |
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| Lists: | pgsql-bugs |
On Thu, 10 Jan 2019 at 12:28, Thomas Munro
<thomas(dot)munro(at)enterprisedb(dot)com> wrote:
> Hmm. Why are those ExecQual() -> false cases not showing up as
> variation in the "Rows Removed by Filter" counter visible in EXPLAIN
> ANALYZE? Then we might have arrived here a lot faster.
> InstrCountFiltered1(node, 1) is executed, but somehow the count
> doesn't make it into the total shown by EXPLAIN.
Good question. They are tracked by the instrumentation, it's just
that show_instrumentation_count() divides by nloops so the additional
filtered rows are lost to the rounding. Removing the / nloops shows
you what you want to see.
--
David Rowley http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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