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help / color / mirror / Atom feedFrom: Jon Zeppieri <[email protected]>
To: Frédéric Yhuel <[email protected]>
Cc: Greg Sabino Mullane <[email protected]>
Cc: [email protected]
Subject: Re: Why a bitmap scan in this case?
Date: Fri, 20 Dec 2024 16:01:57 -0500
Message-ID: <CAKfDxxzb_=qfQy2YEDyb-xKJ78_F=iRY_-_zo4RdzQGUc5QX3w@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
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<[email protected]>
<[email protected]>
On Fri, Dec 20, 2024 at 4:57 AM Frédéric Yhuel
<[email protected]> wrote:
>
>
>
> On 12/20/24 09:16, Frédéric Yhuel wrote:
> >
> >
> > 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
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Subject: Re: Why a bitmap scan in this case?
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