Martin Below <machtin.below@xxxxxxxxxxxxxx> writes: > Why is "idx_wrong" used (which only includes one of the fields > queried) instead of idx_correct (which contains both fields)? It's not immediately clear that that choice is "wrong". A two-column index is bigger and hence more expensive to search than a one-column index --- perhaps quite substantially so, given this particular combination of datatypes. The planner is probably estimating that the expires_on condition is selective enough that nothing much will be gained by using the two-column index. If that's wrong (which is not proven by your example) you might be able to fix it by increasing the stats target for the table. Also, if you haven't customized effective_cache_size, increasing that makes large indexes look cheaper to use. regards, tom lane -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general
