On Thu, 29 Jan 2004, Reece Hart wrote: > I have a large query which I would like to place in a view. The explicit > query is sufficiently fast, but the same query as a view is much slower > and uses a different plan. I would appreciate an explanation of why this > is, and, more importantly whether/how I might coax the view to use a > different plan.
Well, in general select distinct on (A) A, B from table where B=10 order by A,B; is not always the same as select * from (select distinct on (A) A, B from table order by A,B) foo where B=10; If A is not unique, then given two rows of the same A value one with B=10 and one with another B value less than 10, the former is guaranteed to give you an A,10 row, the latter will give no such row AFAICS. If A is unique then the two queries are equivalent, but then distinct on (A) isn't terribly meaningful. ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster
