Brian McCane wrote: > On Thu, 14 Feb 2002, Tom Lane wrote: > > > Bruce Momjian <[EMAIL PROTECTED]> writes: > > > In fact, I am unsure why you are specifying the primary column in the > > > ORDER BY anyway if you know it will be a single value, except perhaps to > > > try and get it to use the index, right? > > > > Exactly. The sort ordering of the index is (col1,col2) while the > > query as originally written wanted an ordering of (col2 desc). > > The planner's not smart enough to realize that since the WHERE > > constrains col1 to a single value, you could pretend the query > > requests an ordering of (col1 desc, col2 desc) which is compatible > > with the index. > > > > regards, tom lane > > > > The annoying thing is that it is smart enough to get the correct index, I > have another index that has the right col1, but different col2. It seems > it should be possible to have the optimizer leave col1 in a "high > impedence" state, and then allow col2 to make a decision. I have not > looked at the code, but if we have a known value for col1 as a constant, > I would think we could let subsequent information make the decision and > then just bubble it up to the top.
Tom, do we have a TODO item here? -- Bruce Momjian | http://candle.pha.pa.us [EMAIL PROTECTED] | (610) 853-3000 + If your life is a hard drive, | 830 Blythe Avenue + Christ can be your backup. | Drexel Hill, Pennsylvania 19026 ---------------------------(end of broadcast)--------------------------- TIP 1: subscribe and unsubscribe commands go to [EMAIL PROTECTED]
