On Thu, Aug 31, 2006 at 03:36:25PM +0200, Csaba Nagy wrote: > On Thu, 2006-08-31 at 15:19, Peter Eisentraut wrote: > > OK, why don't you work out an example. Let's look at this query: > > SELECT * FROM t1 WHERE a LIKE $1; > > What two plans would you prepare? > if substring($1 from 1 for 1) != '%' then > use plan 1 (see below); > else > use plan 2 (see below); > end if;
It would be cool if PostgreSQL did this - but I think it is also true that anybody (or JDBC) who tried to prepare a plan in the cases that are known to cause problems, is making a mistake. While on the 'it would be cool' subject - I think it might be cool if the prepare statement took sample arguments that could be used to prepare the plans with. "Prepare a plan that would work best with these arguments." Then JDBC could prepare both plans for you - if it was smart enough... :-) Cheers, mark -- [EMAIL PROTECTED] / [EMAIL PROTECTED] / [EMAIL PROTECTED] __________________________ . . _ ._ . . .__ . . ._. .__ . . . .__ | Neighbourhood Coder |\/| |_| |_| |/ |_ |\/| | |_ | |/ |_ | | | | | | \ | \ |__ . | | .|. |__ |__ | \ |__ | Ottawa, Ontario, Canada One ring to rule them all, one ring to find them, one ring to bring them all and in the darkness bind them... http://mark.mielke.cc/ ---------------------------(end of broadcast)--------------------------- TIP 9: In versions below 8.0, the planner will ignore your desire to choose an index scan if your joining column's datatypes do not match