kimaidou <kimaidou@xxxxxxxxx> writes: > It seems PostgreSQL does not use the index parcelles_dep_idx on "dep" (text > field), even if the corresponding number of lines for this WHERE clause is > a smal subset of the entire data: > approx 6M against 80M in total 6M out of 80M rows is not a "small subset". Typically I'd expect the planner to use an index-based scan for up to 1 or 2 percent of the table. Beyond that, you're going to be touching most pages of the table anyway. You can try reducing random_page_cost to favor indexscans, but you might not find that the query gets any faster. regards, tom lane
