Horton

Re: Division in dynahash.c due to HASH_FFACTOR

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: David Rowley <dgrowleyml@gmail.com>, Jakub Wartak <Jakub.Wartak@tomtom.com>, Alvaro Herrera <alvherre@2ndquadrant.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2020-09-19T01:30:56Z
Lists: pgsql-hackers 
I wrote:
> ISTM that getting rid of the division obviates the concern that the
> nentries condition is too expensive,

Also, we could make it slightly cheaper yet, by changing the condition
to

            hctl->freeList[0].nentries > (long) (hctl->max_bucket)

ie drop the +1.  I'd argue that this is actually a more faithful
rendition of the previous condition, since what we had before was
basically

            hctl->freeList[0].nentries >= (long) (hctl->max_bucket + 1)

			regards, tom lane

Commits

  1. Code review for dynahash change.

  2. Remove large fill factor support from dynahash.c.