Sebastian Rychter wrote:
Hi, I'm executing a query through psql ODBC which is taking around 2 minutes
to complete. When I run it from PgAdmin it takes less than 3 seconds.
The query itself has :
. 15 inner joins (from just around 10 different tables - the other inner
joins are using different aliases for the same tables)
. Select statement returns 1 field.
. the testing database is selecting only 1 record.
Taking a look at the explain analyze report, I see they are both quite the
same and tested the ODBC driver through Visual Foxpro and Vb.NET as well,
taking both around 2 minutes to finish.
Are you using prepared statements (or might the driver be doing so for
you) ?
A common question here arises from the query planner making different
decisions for a query based on whether or not it can see the values of
query parameters. Consider:
SELECT something FROM tablex WHERE somethingelse = ?
vs
SELECT something FROM tablex WHERE somethingelse = 4
My understanding is that if only (say) 0.1% of records have
`somethingelse' = 4 and there's an index on `somethingelse' the planner
will probably use the index for the second query. For the first query it
won't know to use the index, especially if there are also values for
`somethingelse' that occur a lot.
Try running your query in psql/pgadmin using PREPARE and EXECUTE and see
if you get the same result.
--
Craig Ringer
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