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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 |
