When I read the source code about the hashjoin, I was very confused that the postgresql define the NTUP_PER_BUCKET value as 10. Since this value is used to estimate the tuple count in one bucket, is it better if we have a smaller value? I have not done some experiments, but it seems that we could archive less hash collisions and better performance if we decrease the value. So could anyone explain to me that why we define NTUP_PER_BUCKET as 10? If there exists a specified situation that we would get worse performance or some troubles if set NTUP_PER_BUCKET to 1 or 2?
Thanks very much. -- View this message in context: http://postgresql.1045698.n5.nabble.com/why-postgresql-define-NTUP-PER-BUCKET-as-10-not-other-numbers-smaller-tp5806472.html Sent from the PostgreSQL - hackers mailing list archive at Nabble.com. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
