Re: Why a bitmap scan in this case? - Mailing list pgsql-performance

On Fri, Dec 20, 2024 at 4:57 AM Frédéric Yhuel
<frederic.yhuel@dalibo.com> wrote:
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> On 12/20/24 09:16, Frédéric Yhuel wrote:
> >
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> > On 12/19/24 20:09, Jon Zeppieri wrote:
> >> The table is freshly vacuumed. If I disable bitmap scans, it will do
> >> an index only scan, which performs better. For the bitmap heap scan,
> >> it says "Heap Blocks: exact=27393," whereas for the index only scan,
> >> it's "Heap Fetches: 27701."
> >
> > So you have 100% heap fetches. Are you sure that your table is freshly
> > vacuumed? Please note that VACUUM FULL doesn't create the visibility
> > map, so you still have to run a plain VACUUM for this.

Ah, thanks -- I didn't know that. -J