On 27/05/2010 11:33 PM, Craig Ringer wrote:
On 21/05/2010 9:54 PM, Tyler Hildebrandt wrote:
We're using a function that when run as a select statement outside of the
function takes roughly 1.5s to complete whereas running an identical
query within a function is taking around 55s to complete.
We are lost as to why placing this query within a function as opposed to
substituting the variables in a select statement is so drastically
different.
This is a frequently asked question. It's the same issue as with
prepared queries, where the planner has to pick a more general plan when
it doesn't know the value of a parameter. The short answer is "work
around it by using EXECUTE ... USING to invoke your query dynamically".
( Oddly, this FAQ doesn't seem to be on the FAQ list at
http://wiki.postgresql.org/wiki/FAQ )
Added as:
http://wiki.postgresql.org/wiki/FAQ#Why_is_my_query_much_slower_when_run_as_a_prepared_query.3F
and the subsequent entry too.
Comments, edits, clarification appreciated. I know it's not as well
written as it could be, could use archive links, etc; it's just pass 1.
--
Craig Ringer
--
Sent via pgsql-performance mailing list (pgsql-performance@xxxxxxxxxxxxxx)
To make changes to your subscription:
http://www.postgresql.org/mailpref/pgsql-performance
