On Tue, 28 Mar 2006 09:30:54 +0100
Simon Riggs <simon@xxxxxxxxxxxxxxx> threw this fish to the penguins:
> On Mon, 2006-03-27 at 13:47 -0500, george young wrote:
>
> > Table sizes: parameters has 2.1512e+07 tuples, run_opsets has 211745 tuples.
> >
> > explain analyze SELECT ro.run, ro.opset_num, p.step_num FROM run_opsets ro, parameters p WHERE ro.run = p.run AND ro.opset_num = p.opset_num and ro.run='team9';
> > QUERY PLAN
> > --------------------------------------------------------------------------------------------------------------------------------------------
> > Nested Loop (cost=2.16..7957.40 rows=6707 width=22) (actual time=14.986..70197.129 rows=43050 loops=1)
> > -> Index Scan using run_opsets_pkey on run_opsets ro (cost=0.00..128.75 rows=71 width=18) (actual time=0.386..62.959 rows=263 loops=1)
> > Index Cond: (run = 'team9'::text)
> > -> Bitmap Heap Scan on parameters p (cost=2.16..109.93 rows=27 width=22) (actual time=1.591..266.211 rows=164 loops=263)
> > Recheck Cond: (('team9'::text = p.run) AND ("outer".opset_num = p.opset_num))
> > -> Bitmap Index Scan on parameters_idx (cost=0.00..2.16 rows=27 width=0) (actual time=1.153..1.153 rows=164 loops=263)
> > Index Cond: (('team9'::text = p.run) AND ("outer".opset_num = p.opset_num))
> > Total runtime: 70237.727 ms
> > (8 rows)
>
> The planner appears to be underestimating the number of rows retrieved
> in both cases, then multiplying them together to make it worse.
> Multi-column indexes provide less accurate estimates (right now).
>
> Looks like a hash join might be faster. What is your work_mem set to?
work_mem= 1024
> Can you SET enable_nestloop=off and rerun the EXPLAIN ANALYZE?
newschm3=> set enable_nestloop=off ;
SET
newschm3=> explain analyze SELECT ro.run, ro.opset_num, p.step_num FROM run_opsets ro, parameters p WHERE ro.run = p.run AND ro.opset_num = p.opset_num and ro.run='team9';
QUERY PLAN
----------------------------------------------------------------------------------------------------------------------------------------------------
Merge Join (cost=34177.87..34291.36 rows=6707 width=22) (actual time=68421.681..68547.686 rows=43050 loops=1)
Merge Cond: ("outer".opset_num = "inner".opset_num)
-> Sort (cost=130.93..131.11 rows=71 width=18) (actual time=107.744..107.901 rows=263 loops=1)
Sort Key: ro.opset_num
-> Index Scan using run_opsets_pkey on run_opsets ro (cost=0.00..128.75 rows=71 width=18) (actual time=57.641..106.096 rows=263 loops=1)
Index Cond: (run = 'team9'::text)
-> Sort (cost=34046.94..34070.02 rows=9231 width=22) (actual time=68301.325..68358.087 rows=43050 loops=1)
Sort Key: p.opset_num
-> Bitmap Heap Scan on parameters p (cost=272.31..33438.97 rows=9231 width=22) (actual time=526.462..67363.577 rows=43050 loops=1)
Recheck Cond: ('team9'::text = run)
-> Bitmap Index Scan on parameters_idx (cost=0.00..272.31 rows=9231 width=0) (actual time=483.500..483.500 rows=43050 loops=1)
Index Cond: ('team9'::text = run)
Total runtime: 68595.868 ms
(13 rows)
-- George Young
--
"Are the gods not just?" "Oh no, child.
What would become of us if they were?" (CSL)
