On Thu, Sep 03, 2020 at 05:53:43PM -0700, Jeff Davis wrote:
On Tue, 2020-09-01 at 23:19 +0200, Tomas Vondra wrote:
FWIW any thoughts about the different in temp size compared to
CP_SMALL_TLIST?
Are you referring to results from a while ago? In this thread I don't
see what you're referring to.
I tried in a simple case on REL_13_STABLE, with and without the
CP_SMALL_TLIST change, and I saw only a tiny difference. Do you have a
current case that shows a larger difference?
I'm referring to the last charts in the message from July 27, comparing
behavior with CP_SMALL_TLIST fix vs. master (which reverted/replaced the
CP_SMALL_TLIST bit).
Those charts show that the CP_SMALL_TLIST resulted in smaller temp files
(per EXPLAIN ANALYZE the difference is ~25%) and also lower query
durations (also in the ~25% range).
I can repeat those tests, if needed.
[1]
https://www.postgresql.org/message-id/20200724012248.y77rpqc73agrsvb3@development
The only thing I can think of that might change is the size of the null
bitmap or how fields are aligned.
Maybe. Not sure.
regards
--
Tomas Vondra http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
