| From: | Ranier Vilela <ranier(dot)vf(at)gmail(dot)com> |
|---|---|
| To: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
| Cc: | pgsql-performance(at)postgresql(dot)org, hippysoyboy(at)gmail(dot)com, postgres(at)binarykeep(dot)com |
| Subject: | Re: Plan not skipping unnecessary inner join |
| Date: | 2020-05-17 14:05:39 |
| Message-ID: | CAEudQApPBa1BDcktwY3oc6hvRNs9hrHJNALfcJUc7gHvbhZ7fw@mail.gmail.com |
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| Lists: | pgsql-performance |
Em dom., 17 de mai. de 2020 às 10:31, Justin Pryzby <pryzby(at)telsasoft(dot)com>
escreveu:
> On Sun, May 17, 2020 at 09:32:47AM -0300, Ranier Vilela wrote:
> > I redid the same tests with vanila postgres and with empty tables.
> > I'm surprised, why does the plan have 2550 rows in explain?
>
> That's the *estimated* rowcount.
>
> The planner tends to ignore table statistics which say the table is empty,
> since that can lead to a terrible plan if it's not true (stats are out of
> date
> or autovacuum threshold not hit).
>
Thanks for the explanation.
regards,
Ranier Vilela
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