On Sun, Oct 16, 2005 at 05:09:57PM -0400, Greg Stark wrote: > Tom Lane <[EMAIL PROTECTED]> writes: > > Certainly, if you do not supply a LIMIT, there is no justification > > at all for expecting the planner to prefer fast-start over > > minimum-total-cost. > > Well figuring out when to prefer one or the other is a hard problem. > Fundamentally the server simply does not have the information it needs to > determine that available.
Umm, not really. Notice how EXPLAIN has two numbers: time to first row, time to last row. If you add limit 1 it will favour plans that return the first row quickly. If you don't it'll favour plans that have the lowest total execution time, even if the first tuple takes longer. > (I think there really ought to be a bit in the protocol that the client sends > with the query to indicate which is needed. That would be cleaner than > Oracle's /*+ FIRST_ROW */ and /*+ ALL_ROWS */ hints.) It's called LIMIT and has been supported for a long time. Have a nice day, -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > Patent. n. Genius is 5% inspiration and 95% perspiration. A patent is a > tool for doing 5% of the work and then sitting around waiting for someone > else to do the other 95% so you can sue them.
pgpBAtfyMK6pe.pgp
Description: PGP signature
