Simon Riggs wrote:
On Tue, 2007-01-30 at 15:33 +0600, Igor Lobanov wrote:
explain analyze select distinct a, b from tbl
EXPLAIN ANALYZE output is:
Unique (cost=500327.32..525646.88 rows=1848 width=6) (actual
time=52719.868..56126.356 rows=5390 loops=1)
-> Sort (cost=500327.32..508767.17 rows=3375941 width=6) (actual
time=52719.865..54919.989 rows=3378864 loops=1)
Sort Key: a, b
-> Seq Scan on tbl (cost=0.00..101216.41 rows=3375941
width=6) (actual time=16.643..20652.610 rows=3378864 loops=1)
Total runtime: 57307.394 ms
All your time is in the sort, not in the SeqScan.
Increase your work_mem.
Well, even if the sort was instant it's only going to get him down to
20secs.
--
Richard Huxton
Archonet Ltd
