So, I defragged my disk and reran my original query and it got a little better, but still far higher than I'd like. I then rebuilt (dropped and recreated) the ad_log_date_all index and reran the query and it is quite a bit better:
# explain analyze select * from ad_log where date(start_time) < date('2009-03-31') and date(start_time) >= date('2009-03-30');
QUERY PLAN
----------------------------------------------------------------------------------------------------------------------------------------------
Bitmap Heap Scan on ad_log (cost=64770.21..3745596.62 rows=2519276 width=32) (actual time=1166.479..13862.107 rows=2275167 loops=1)
Recheck Cond: ((date(start_time) < '2009-03-31'::date) AND (date(start_time) >= '2009-03-30'::date))
-> Bitmap Index Scan on ad_log_date_all (cost=0.00..64140.39 rows=2519276 width=0) (actual time=1143.582..1143.582 rows=2275167 loops=1)
Index Cond: ((date(start_time) < '2009-03-31'::date) AND (date(start_time) >= '2009-03-30'::date))
Total runtime: 14547.885 ms
During the query the disk throughput peaked at 30MB/s and was mostly at around 20MB/s, much better.
So, a few questions:
What can I do to prevent the index from getting bloated, or in whatever state it was in?
What else can I do to further improve queries on this table? Someone suggested posting details of my conf file. Which settings are most likely to be useful for this?
Any other suggestions?
Thanks,
--Rainer
