Andrew Sullivan <[EMAIL PROTECTED]> writes: > The statistics on transaction_date and product_id are set to 1000. > Everything is all analysed nicely. But I'm getting a poor plan, > because of an estimate that the number of rows to be returned is > about double how many actually are:
> explain analyse select * from transactions_posted where > transaction_date >= '2003-9-1' and transaction_date < '2003-10-1' and > product_id = 2; Are the estimates accurate for queries on the two columns individually, ie ... where transaction_date >= '2003-9-1' and transaction_date < '2003-10-1' ... where product_id = 2 If so, the problem is that there's a correlation between transaction_date and product_id, which the system cannot model because it has no multi-column statistics. However, given that the estimate is only off by about a factor of 2, you'd still be getting the wrong plan even if the estimate were perfect, because the estimated costs differ by nearly a factor of 3. Given the actual runtimes, I'm thinking maybe you want to reduce random_page_cost. What are you using for that now? regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 4: Don't 'kill -9' the postmaster