On Mon, Sep 11, 2017 at 04:43:46PM +0900, Yuto Hayamizu wrote: > Hi hackers, > > Currently, cost of a filter with multiple clauses is estimated by > summing up estimated cost of each clause. As long as a filter > consists of simple clauses and its cost is fairly small, it works > fine. However, when there exists some heavy clauses (like SubQuery or > user-defined functions) and most of tuples are filtered by other > simple clauses, total cost is likely to be overestimated. An attached > patch mitigates this overestimation by using selectivity estimation of > subsets of clauses in a filter.
I've taken the liberty of adding this to the upcoming commitfest. Best, David. -- David Fetter <david(at)fetter(dot)org> http://fetter.org/ Phone: +1 415 235 3778 AIM: dfetter666 Yahoo!: dfetter Skype: davidfetter XMPP: david(dot)fetter(at)gmail(dot)com Remember to vote! Consider donating to Postgres: http://www.postgresql.org/about/donate -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
