Re: BitmapHeapScan streaming read user and prelim refactoring

From: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>
To: Melanie Plageman <melanieplageman(at)gmail(dot)com>
Cc: Andres Freund <andres(at)anarazel(dot)de>, Pg Hackers <pgsql-hackers(at)postgresql(dot)org>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, Nazir Bilal Yavuz <byavuz81(at)gmail(dot)com>
Subject: Re: BitmapHeapScan streaming read user and prelim refactoring
Date: 2024-02-28 19:23:28
Message-ID: d0a5199d-f195-4378-8ac1-fa2534192041@enterprisedb.com
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On 2/28/24 15:56, Tomas Vondra wrote:
>> ...
>
> Sure, I can do that. It'll take a couple hours to get the results, I'll
> share them when I have them.
>

Here are the results with only patches 0001 - 0012 applied (i.e. without
the patch introducing the streaming read API, and the patch switching
the bitmap heap scan to use it).

The changes in performance don't disappear entirely, but the scale is
certainly much smaller - both in the complete results for all runs, and
for the "optimal" runs that would actually pick bitmapscan.

FWIW I'm not implying the patch must 100% maintain the current behavior,
or anything like that. At this point I'm more motivated to understand if
this change in behavior is expected and/or what this means for users.

regards

--
Tomas Vondra
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

Attachment Content-Type Size
bitmapscan-refactoring-results-optimal.pdf application/pdf 174.1 KB
bitmapscan-refactoring-results.pdf application/pdf 479.9 KB

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