On Thursday, June 06, 2013 1:56 PM Ghislain ROUVIGNAC wrote: > Hello,
> We have a strange issue related to a prepared statement. > We have two equals queries where the sole difference is in the limit. > - The first is hard coded with limit 500. > - The second is prepared with limit $1 ($1 is bound to 500). > PostgreSQL give us two different plans with a huge execution time for the prepared query: It can generate different plan for prepared query, because optimizer uses default selectivity in case of bound parameters (in your case limit $1). > We met the same behaviour with both : > - PostgreSQL 8.4.8 on Windows 2008 (Prod) > - PostgreSQL 8.4.8 and 8.4.17 on Windows 7 (Dev) >From PostgreSQL 9.2, it generates plan for prepared query during execution (Execute command) as well. So I think you will not face this problem in PostgreSQL 9.2 and above. With Regards, Amit Kapila. -- Sent via pgsql-performance mailing list (pgsql-performance@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-performance
