Re: Strange discrepancy in query performance...

"Jason L. Buberel" <jason(at)buberel(dot)org> writes:
> In my syslog output, I see entries indicating that the
> JDBC-driver-originated query on a table named 'city_summary' are taking
> upwards of 300 seconds:

> Oct 1 18:27:47 srv3 postgres-8.2[1625]: [12-1]
> LOG: duration: 307077.037 ms execute S_42: select * from city_summary
> where state = $1 and city_master_id = $2 and res_type =
> 'single_family' and date = $3
> and range = 90 and zip = $4 and quartile = '__ALL'
> DETAIL: parameters: $1 = 'CA', $2 = '291', $3 = '2007-09-28', $4 = '__ALL'

> However, if I run the same query on the same host at the same time that
> the Java application is running, but from the psql command line, it
> takes only 0.37 seconds:

>>> time /opt/postgres-8.2.4/bin/psql --port 54824 -U postgres -d
> altos_research -c 'select fact_id from city_summary where state =
> \'CA\' and city_master_id = 291 and zip = \'__ALL\' and quartile =
> \'__ALL\' and res_type = \'single_family\' and range = \'90\' and date =
> \'2007-09-28\';'

This is not, in fact, the same query --- the JDBC-originated one is
parameterized, which means it very possibly has a different plan
(since the planner doesn't know the particular values to plan for).

Try using PREPARE and EXPLAIN EXECUTE to examine the plan that is
being produced for the parameterized query.

regards, tom lane