On Mon, Sep 12, 2005 at 09:43:57AM -0400, Reid Thompson wrote: > assume a table of 10 columns, three of which are fname, lname, and dob. > If an index is created on (fname, lname, dob), will a query that > utilizes two of the columns ( select 'data' from table where fname = 'X' > and lname = 'Y') utilize the index? See "Multicolumn Indexes" in the "Indexes" chapter of the documentation. http://www.postgresql.org/docs/8.0/interactive/indexes-multicolumn.html You can use EXPLAIN to see whether the planner will use an index for a particular query. http://www.postgresql.org/docs/8.0/interactive/performance-tips.html#USING-EXPLAIN Note, however, that the planner will ignore an index and use a sequential scan if it thinks the latter will be faster, so if you want to see whether the query *can* use an index (as opposed to *will* use it) then you could execute "SET enable_seqscan TO off" and then run EXPLAIN (don't forget to RESET enable_seqscan or SET it back to "on" when you're done testing). -- Michael Fuhr ---------------------------(end of broadcast)--------------------------- TIP 1: if posting/reading through Usenet, please send an appropriate subscribe-nomail command to majordomo@xxxxxxxxxxxxxx so that your message can get through to the mailing list cleanly
