"Ow Mun Heng" <Ow.Mun.Heng@xxxxxxx> writes: > On Mon, 2007-09-03 at 11:31 +0100, Gregory Stark wrote: >> "Ow Mun Heng" <Ow.Mun.Heng@xxxxxxx> writes: >> > >> > How can I persuade PG to use the index w/o resorting to setting seqscan >> > = false >> >> The usual knob to fiddle with is random_page_cost. If your database fits >> mostly in memory you may want to turn it down from the default of 4 to >> something closer to 1. > > I tried down to 0.4 before it resorted to using the index. The DB > shouldn't fit into memory (I think) that table alone has ~8million rows > at ~1.5G size Values under 1 are nonsensical. Basically being as low as 1 means you're telling the database that a random access i/o takes the same amount of time as a sequential i/o. (Actually we have sequential_page_cost now so I guess instead of "1" I should say "the same as sequential_page_cost" but I'm assuming you haven't modified sequential_page_cost from the default of 1 have you?) -- Gregory Stark EnterpriseDB http://www.enterprisedb.com ---------------------------(end of broadcast)--------------------------- TIP 5: don't forget to increase your free space map settings
