Mikko Partio wrote:
On 6/20/07, *Tom Lane* <tgl@xxxxxxxxxxxxx <mailto:tgl@xxxxxxxxxxxxx>> wrote:
"Mikko Partio" <mpartio@xxxxxxxxx <mailto:mpartio@xxxxxxxxx>> writes:
> Index Scan using tbl_20070601_pkey on tbl_20070601 t1
> (cost=0.00..365.13rows=13 width=137) (actual time=
> 120.83..10752.64 rows=539 loops=1)
> Index Cond: ((validtime >= 20070602000000::bigint) AND
(validtime <=
> 20070602235500::bigint) AND (latitude = 60.2744::double
precision) AND
> (longitude = 26.4417::double precision))
> Filter: (parname = 'temperature'::character varying)
You do realize that's going to scan the entire index range from
20070602000000 to 20070602235500?
If this is a typical query you'd be better off putting the lat/long
columns first in the index.
regards, tom lane
Thanks for the reply.
Adding a new index does not speed up the query (although the planner
decides to use the index):
db=# create index tbl_20070601_latlonvalidpar_index on tbl_20070601
(latitude,longitude,validtime,parname);
CREATE INDEX
db=# explain analyze select * from tbl_20070601 where validtime between
20070602000000 and 20070602235500 and latitude= 60.2744 and
longitude=26.4417 and parname in ('temperature');
QUERY PLAN
-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
Index Scan using tbl_20070601_latlonvalidpar_index on tbl_20070601 t1
(cost=0.00..29.18 rows=13 width=137) (actual time=3471.94..31542.90
rows=539 loops=1)
Index Cond: ((latitude = 60.2744::double precision) AND (longitude =
26.4417::double precision) AND (validtime >= 20070602000000::bigint) AND
(validtime <= 20070602235500::bigint) AND (parname =
'temperature'::character varying))
Total runtime: 31544.48 msec
(3 rows)
This is a very typical query and therefore it should be made as fast as
possible. There are several tables like this rowcount ranging from 3
million to 13 million. I have some possibilities to modify the queries
as well as the tables, but the actual table structure is hard coded.
Any other suggestions?
Try increasing your default_statistics_target and rerunning explain
analyze. Secondly try increasing your work_mem.
Joshua D. Drake
Regards
MP
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