On Mon, Jun 13, 2005 at 09:51:57 -0500, John A Meinel <[EMAIL PROTECTED]> wrote: > > I don't know if there are specific reasons why not, other than just not > being implemented yet. It might be tricky to get it correct (for > instance, how do you know which columns can be added, which ones will be > constant) Perhaps you could just potentially add the WHERE items if they > have an equality constraint with a constant. But I'm guessing there are > more cases than that where the optimization could be performed.
I think there is already some intelligence about which expressions are constant in particular parts of a plan. I think you need to be able to do two things. One is to drop constant expressions from order by lists. The other is when looking for an index to produce a specific ordering, to ingore leading constant expressions when comparing to the order by expressions. > Also, the more options you give the planner, the longer it takes on > average to plan any single query. Yes, it is beneficial for this use > case, but does that balance out slowing down all the other queries by a > tiny bit. But there aren't that many possible indexes, so I don't expect this will slow things down much more than the current check for potentially useful indexes. ---------------------------(end of broadcast)--------------------------- TIP 7: don't forget to increase your free space map settings