Pavan Deolasee wrote: > Amitabh Kant <amitabhkant@xxxxxxxxx> wrote: >> Our scripts automatically add "LIMIT ALL" & "OFFSET 0" to every >> select query if no values are passed on for these parameters. I >> remember reading through the mailing list that it's better not >> to pass them if they are not needed as they add a cost to the >> query plan. Is this the case, or am i looking at a very minor >> optimization. >> > > I would tend to think that is the latter. While undoubtedly > limit/offset clause will add another node during query planning > and execution, AFAICS the OFFSET 0 and LIMIT ALL cases are > optimized to a good extent. So the overhead of having them will > not be significant. I ran some quick tests on my i7 under Linux. Plan time was increased by about 40 microseconds (based on EXPLAIN runtime) and added a limit node to the plan. Execution time on a SELECT * FROM tenk1 in the regression database went up by 1.35 ms on fully cached runs. -Kevin -- Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
