Carlos Moreno <moreno_pg@xxxxxxxxxxx> writes: > But I think the problem is that this particular table had not been > vacuum analyzed after having inserted the 20000 records (the > query planner was giving me seq. scan when the table had about > a dozen records --- and seq. scan was, indeed, 10 times faster; > as a test, to make sure that the query planner would do the right > thing when the amount of records was high, I inserted 20000 > records, and tried again --- now the seq. scan was 100 times > slower, but it was still chosen (at that point was that I did a > search through the archives and then posted the question). > But now, after reading the replies, I did a vacuum analyze for > this table, and now the query planner is choosing the Index > scan. One reason you might consider updating is that newer versions check the physical table size instead of unconditionally believing pg_class.relpages/reltuples. Thus, they're much less likely to get fooled when a table has grown substantially since it was last vacuumed or analyzed. regards, tom lane
