Re: Small optimization with expanding dynamic hash table

From: Rahila Syed <rahilasyed90(at)gmail(dot)com>
To: cca5507 <cca5507(at)qq(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: Small optimization with expanding dynamic hash table
Date: 2025-07-08 08:32:50
Message-ID: CAH2L28vccNhRsyd1PfzdGeumKJofTh7SABA1Pmoyo_vwks=mAA@mail.gmail.com
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Hi,

Yes, for example:
>
> low_mask: 0x011, high_mask: 0x111, old_bucket: 0x010, new_bucket: 0x110
>
> The old_bucket's hash value like 0x***010 or 0x***110, the later is in the
> old_bucket is because we didn't have new_bucket before, so only hash value
> like 0x***110 needs relocation: hashvalue & (low_mask + 1) != 0
>
>
Thanks for explaining, that clarifies things for me.
It may be worthwhile to check if this change has led to any performance
improvements.

Thank you,
Rahila syed

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