>From: Christian Rengstl >Subject: Optimizing PostgreSQL for Windows > >Hi list, > >I have the following query: >select t.a1, t.a2 from table1 t inner join table2 s >using(id) where t.pid='xyz' and s.chromosome=9 order by s.pos; > >" -> Bitmap Heap Scan on table1 t (cost=388.25..27357.57 >rows=22286 width=23) (actual time=112.595..32989.663 rows=22864 loops=1)" >" Recheck Cond: ((pid)::text = 'xyz'::text)" >" -> Bitmap Index Scan on idx_table1 (cost=0.00..382.67 >rows=22286 width=0) (actual time=103.790..103.790 rows=22864 loops=1)" >" Index Cond: ((pid)::text = 'xyz'::text)" The bitmap heap scan on table1 seems very slow. What version of Postgres are you using? There were performance enhancements in 8.1 and 8.2. What kind of a hard drive are you using? I would guess a single SATA drive would give you better performance than that, but I don't know for sure. Do you regularly vacuum the table? Not enough vacuuming can lead to tables filled with dead rows, which can increase the amount of data needing to be scanned considerably. Dave ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
