> On 6 Nov 2023, at 14:31, Alvaro Herrera <alvherre@alvh.no-ip.org> wrote: > > dynahash is notoriously slow, which is why we have simplehash.h since > commit b30d3ea824c5. Maybe we could use that instead.
Dynahash has lock partitioning. Simplehash has not, AFAIK. The thing is we do not really need a hash function - pageno is already a best hash function itself. And we do not need to cope with collisions much - we can evict a collided buffer.
Given this we do not need a hashtable at all. That’s exact reasoning how banks emerged, I started implementing dynahsh patch in April 2021 and found out that “banks” approach is cleaner. However the term “bank” is not common in software, it’s taken from hardware cache.
I agree that we don't need the hash function to generate hash value out of pageno which itself is sufficient, but I don't understand how we can get rid of the hash table itself -- how we would map the pageno and the slot number? That mapping is not needed at all?
