Simon Riggs <[EMAIL PROTECTED]> writes: > On Mon, 2005-04-25 at 11:23 -0400, Tom Lane wrote: >> It's not just the scan --- you also have to sort, or something like >> that, if you want to count distinct values. I doubt anyone is really >> going to consider this a feasible answer for large tables.
> Assuming you don't use the HashAgg plan, which seems very appropriate > for the task? (...but I understand the plan otherwise). The context here is a case with a very large number of distinct values... keep in mind also that we have to do this for *all* the columns of the table. A full-table scan for each column seems right out to me. regards, tom lane ---------------------------(end of broadcast)--------------------------- TIP 5: Have you checked our extensive FAQ? http://www.postgresql.org/docs/faq