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help / color / mirror / Atom feedFrom: Robert Haas <[email protected]>
To: Melanie Plageman <[email protected]>
Cc: Tomas Vondra <[email protected]>
Cc: Andres Freund <[email protected]>
Cc: PostgreSQL Hackers <[email protected]>
Cc: Georgios <[email protected]>
Cc: Thomas Munro <[email protected]>
Cc: Konstantin Knizhnik <[email protected]>
Cc: Dilip Kumar <[email protected]>
Subject: Re: index prefetching
Date: Wed, 14 Feb 2024 12:40:14 +0530
Message-ID: <CA+TgmoZemqR60MoiPN+R0qMe2XDYtOe=Tr1+3rX7S1Uua_C6wA@mail.gmail.com> (raw)
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On Thu, Feb 8, 2024 at 3:18 AM Melanie Plageman
<[email protected]> wrote:
> - kill prior tuple
>
> This optimization doesn't work with index prefetching with the current
> design. Kill prior tuple relies on alternating between fetching a
> single index tuple and visiting the heap. After visiting the heap we
> can potentially kill the immediately preceding index tuple. Once we
> fetch multiple index tuples, enqueue their TIDs, and later visit the
> heap, the next index page we visit may not contain all of the index
> tuples deemed killable by our visit to the heap.
Is this maybe just a bookkeeping problem? A Boolean that says "you can
kill the prior tuple" is well-suited if and only if the prior tuple is
well-defined. But perhaps it could be replaced with something more
sophisticated that tells you which tuples are eligible to be killed.
--
Robert Haas
EDB: http://www.enterprisedb.com
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Subject: Re: index prefetching
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