Arjen van der Meijden <acmmailing@xxxxxxxxxxxx> writes: > ... Rewriting it to something like this made the last iteration about as > fast as the first: > SELECT docid, (SELECT work to be done for each document) > FROM documents > WHERE docid IN (SELECT docid FROM documents > ORDER BY docid > LIMIT 1000 > OFFSET ? > ) The reason for this, of course, is that the LIMIT/OFFSET filter is the last step in a query plan --- it comes *after* computation of the SELECT output list. (So does ORDER BY, if an explicit sort step is needed.) So if you have an expensive-to-compute output list, a trick like Arjen's will help. I don't think you can use an "IN" though, at least not if you want to preserve the sort ordering in the final result. regards, tom lane
