On Mon, Jul 27, 2009 at 3:15 PM, Zach Conrad<zach.con...@digitecinc.com> wrote: > While creating a function, I kept getting a large variance in runtime between > the raw query vs. using the function/prepared statement. After talking with > folks on #postgresql, specifically David Fetter, he thought I should mention > it here.
When you PREPARE with a parameter, it generates the plan without knowing specifically which value you intend to substitute at execution time. Obviously, this can affect what plan gets chosen, because it's sort of trying to make a best guess without knowing whether the actual value will be a common one or an uncommon one. I bet if you PREPARE it without the parameter, you'll get the same plan as executing it directly. ...Robert -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
