On Thu, Aug 10, 2006 at 11:00:00AM -0400, Tom Laudeman wrote:
> As far as I can tell (from running actual tests) Postgres will not use a
> multi-column index when the SELECT is constraining on only one of the
> columns in the index.
Excerpt from the 8.1 Release Notes:
* Allow nonconsecutive index columns to be used in a multicolumn
index (Tom)
For example, this allows an index on columns a,b,c to be used in
a query with WHERE a = 4 and c = 10.
If you're querying only on c then an index on (a,b,c) will probably
be slower than an index on (c), but if you have only (a,b,c) then
the planner will consider using it.
--
Michael Fuhr