Re: JDBC/Stored procedure performance issue

Hi Tom,

Is there any way to work out what plan the query is using in side the
function? I think I have a similar problem with a query taking much
longer from inside a function than it does as a select statement.

Regards
Matthew

Tom Lane wrote:
> Claire McLister <mclister(at)zeesource(dot)net> writes:
>
>> When I do an EXPLAIN ANALYZE on one query that returns 3261 rows, it
>> executes in a reasonable 159ms:
>> ...
>> If I issue the same query over JDBC or use a PSQL stored procedure, it
>> takes over 3000 ms, which, of course is unacceptable!
>>
>
> I suspect that the problem is with "groupid = $1" instead of
> "groupid = 57925". The planner is probably avoiding an indexscan
> in the parameterized case because it's guessing the actual value will
> match so many rows as to make a seqscan faster. Is the distribution
> of groupid highly skewed? You might get better results if you increase
> the statistics target for that column.
>
> Switching to something newer than 7.4.x might help too. 8.1 and up
> support "bitmap" indexscans which work much better for large numbers
> of hits, and correspondingly the planner will use one in cases where
> it wouldn't use a plain indexscan.
>
> regards, tom lane
>
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