| From: | Jon Zeppieri <zeppieri(at)gmail(dot)com> |
|---|---|
| To: | Greg Sabino Mullane <htamfids(at)gmail(dot)com> |
| Cc: | pgsql-performance(at)lists(dot)postgresql(dot)org |
| Subject: | Re: Why a bitmap scan in this case? |
| Date: | 2024-12-19 19:19:50 |
| Message-ID: | CAKfDxxwffetLV3UKdLZR_zUOe4odDLges-v7kkTtasfMQ2a2NQ@mail.gmail.com |
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| Lists: | pgsql-performance |
On Thu, Dec 19, 2024 at 2:09 PM Jon Zeppieri <zeppieri(at)gmail(dot)com> wrote:
>
> The row estimate is not good. The query estimates 317919 rows but
> there are only 27701. There is some correlation here; if end_on is
> null, start_on is a lot more likely to be recent, so maybe extended
> statistics would be useful here.
>
Though, given that the index only contains rows where end_on is null,
it seems odd that the planner would estimate more rows than are
present in the index. That said, I have no idea whether the planner
uses that sort of information. -J
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