Remove query results from cache

Hello,

Is there any way to remove the results of certain query, from the memory
cache ?
I´m doing some performance tests, and I need the planner to make his
work every time I run the statements, without changing them.

Running vmstat, I can se the memory cache grows, and the planner do not
'forget' the results of any query until the cache reach 2 Gb (total box
RAM) , or the server is rebooted.

--
[]´s,

André Volpato
ECOM Tecnologia Ltda
andre.volpato@ecomtecnologia.com.br
(41) 3014 2322