On Mon, Mar 3, 2014 at 10:12 PM, Damon Snyder <damon@huddler-inc.com> wrote: > >> Um... I think your problem is a misuse of CTE. Your CTE is building an > intermediate of several thousands of rows only to select a dozen > afterwards. You may want to consider a view or subquery, though I'm > not sure pg will be able to optimize much given your use of window > functions, which forces a materialization of that intermediate result. > > The application requires that we find an element and it's neighbors within a > sorted set at a given offset after filtering by category and status. In the > examples provided, we need position 50000, 6 above, and 6 below. Is there a > way do to that more efficiently without first determining the position of > each element within the set using a window function? How would a subquery > help? > > The only solution I could come up with was to materialize the intermediate > result with the CTE (since you don't know ahead of time how many objects > match the status and category criteria) then use the window to include the > position or index.
You're materializing on a per-query basis. That's no good (as your timings show). Try to find a way to materialize on a more permanent basis.
I cannot give you a specific solution without investing way more time than I would. But consider this: all your queries costs are CPU costs. You need a better algorithm, or better hardware. I doubt you'll find hardware that performs 16 times faster, so you have to concentrate on a better algorithm.
And it's unlikely you'll find a better algorithm without a better data structure. So you need to reorganize your database to make it easier to query. I don't think simple SQL optimizations will get you to your performance goal.