| From: | "Core Studios Inc(dot)" <corestudiosinc(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)anarazel(dot)de>, Matthias van de Meent <boekewurm+postgres(at)gmail(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Andrew Dunstan <andrew(at)dunslane(dot)net>, Melanie Plageman <melanieplageman(at)gmail(dot)com>, Thomas Munro <thomas(dot)munro(at)gmail(dot)com>, Konstantin Knizhnik <knizhnik(at)garret(dot)ru>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>, Alexander Kuzmenkov <akuzmenkov(at)timescale(dot)com> |
| Subject: | Re: Incorrect result of bitmap heap scan. |
| Date: | 2025-09-16 12:55:49 |
| Message-ID: | bd5ea69b-2b96-42b7-998a-13554983b3c5@gmail.com |
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| Lists: | pgsql-hackers |
Following up to correct my previous email: the query plan did not really
change - we see Bitmap Heap Scans even before the upgrade. Therefore,
the query plan doesn't seem to have changed after the upgrade.
However after the upgrade it seems that those queries are doing more
disk IO (increased index_blocks_read in that table).
Thanks in advance
On 9/16/25 3:25 PM, Andres Freund wrote:
> Hi,
>
> On September 16, 2025 7:57:54 AM EDT, "Core Studios Inc." <corestudiosinc(at)gmail(dot)com> wrote:
>> Hello,
>>
>> We noticed a sustained increased in IO Wait of read queries after upgrading from 13.13 to 13.21. Eventually, we narrowed it down to a spike in index_blocks_read of a certain table where Bitmap Heap Scans do happen.
>>
>> Do you think that this change (i.e. removing the optimization) could be what caused this regression?
> You're not providing enough details for us to answer that question. We'd need an explain verbose for the query.
>
> Greetings,
>
> Andres
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