I noticed that when I have an index on (a,b) of table t, and I do an SELECT * FROM t ORDER BY a ASC, it doesn't use the index. When I create a new index of only a, it does use the index. Why is that? And, more importantly, when I do a query involving a merge join of table t, which requires sorting table t, the planner does the sort manually using quicksort, not using the index. The time that step takes is identical to the ORDER BY without using the index. What do I need to do to have Postgres use the index for the merge join? (Postgres 8.3) Thanks! -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
