Message-ID: <e330dc73-4ab3-4794-8fb7-e9486bcb0df7@enterprisedb.com>
Date: Wed, 13 Mar 2024 19:14:36 +0100
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Subject: Re: BitmapHeapScan streaming read user and prelim refactoring
To: Heikki Linnakangas <hlinnaka@iki.fi>, Dilip Kumar
 <dilipbalaut@gmail.com>, Melanie Plageman <melanieplageman@gmail.com>
Cc: Nazir Bilal Yavuz <byavuz81@gmail.com>, Andres Freund
 <andres@anarazel.de>, Pg Hackers <pgsql-hackers@postgresql.org>,
 Thomas Munro <thomas.munro@gmail.com>
References: 
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 <CAAKRu_bQ9a2dB42Tz-mrsR+2MuG-ojRmqbX-x-TC08Uo_RunNw@mail.gmail.com>
 <20240216173559.xiy5xcl5dqmsprns@liskov>
 <20240227015028.knohvy3spaqwk7lf@liskov>
 <20240227142230.nu3ytvcjwouvczlt@liskov>
 <5f3b9d59-0f43-419d-80ca-6d04c07cf61a@iki.fi>
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From: Tomas Vondra <tomas.vondra@enterprisedb.com>
In-Reply-To: <5f3b9d59-0f43-419d-80ca-6d04c07cf61a@iki.fi>
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On 3/13/24 14:34, Heikki Linnakangas wrote:
> ...
> 
> Lots of discussion happening on the performance results but it seems
> that there is no performance impact with the preliminary patches up to
> v5-0013-Streaming-Read-API.patch. I'm focusing purely on those
> preliminary patches now, because I think they're worthwhile cleanups
> independent of the streaming read API.
> 

Not quite true - the comparison I shared on 29/2 [1] shows a serious
regression caused by the 0010 patch. We've been investigating this with
Melanie off list, but we don't have any clear findings yet (except that
it's clearly due to moving BitmapAdjustPrefetchIterator() a bit down.

But if we revert this (and move the BitmapAdjustPrefetchIterator back),
the regression should disappear, and we can merge these preparatory
patches. We'll have to deal with the regression (or something very
similar) when merging the remaining patches.

regards


[1]
https://www.postgresql.org/message-id/91090d58-7d3f-4447-9425-f24ba66e292a%40enterprisedb.com
-- 
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
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