Re: Small optimization with expanding dynamic hash table

Rahila Syed <rahilasyed90@gmail.com>

From: Rahila Syed <rahilasyed90@gmail.com>
To: cca5507 <cca5507@qq.com>
Cc: pgsql-hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-07-08T08:32:50Z
Lists: pgsql-hackers
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