Re: Incorrect result of bitmap heap scan.

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?

Thanks

On 3/5/25 1:12 PM, Matthias van de Meent wrote:
> On Sun, 2 Mar 2025 at 01:35, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> Peter Geoghegan <pg@bowt.ie> writes:
>>> Is everybody in agreement about committing and back patching this fix,
>>> which simply disables the optimization altogether?
>>> I myself don't see a better way, but thought I'd ask before proceeding
>>> with review and commit.
>> If you don't see a clear path forward, then "disable" is the only
>> reasonable choice for the back branches.  Maybe we'll find a fix
>> in future, but it seems unlikely that it'd be back-patchable.
> Agreed.
>
> Here's patch v5 for the master branch (now up to f4694e0f), with no
> interesting changes other than fixing apply conflicts caused by
> bfe56cdf.
>
> Kind regards,
>
> Matthias van de Meent
> Neon (https://neon.tech)