> > --Test 2: This works as I would expect - shows that none of the > > functions are run presumably its going straight for 5 > 2 > > --becuase it recognizes its the cheapest route > > TRUNCATE TABLE log_call; > > SELECT foo.value > > FROM (SELECT (fn_pg_costlyfunction() > 2 OR fn_pg_cheapfunction() > 2 OR > > 5 > 2 ) as value) as foo > That's just constant-folding: x OR TRUE is TRUE. It has exactly > zero to do with the cost of anything. > Offhand I think the behavior you are looking for of choosing to run more > expensive subexpressions later only occurs for top-level WHERE clauses >that are combined with AND. > regards, tom lane Tom thanks for the clarification - based on your comment I verified with these -- fn_pg_cheapfunction() is the only one run as you predicted TRUNCATE TABLE log_call; SELECT true as value WHERE (fn_pg_costlyfunction() > 2 AND fn_pg_cheapfunction() > 5 ); -- fn_pg_costlyfunction() is the only one run - again as predicted by your statement TRUNCATE TABLE log_call; SELECT true as value WHERE (fn_pg_costlyfunction() > 2 OR fn_pg_cheapfunction() > 2 ); It would be really nice if this worked with OR as well. Is it just much harder to deal with the OR case in the planner or was there some other reason why the OR case was left out? Thanks, Regina ----------------------------------------- The substance of this message, including any attachments, may be confidential, legally privileged and/or exempt from disclosure pursuant to Massachusetts law. It is intended solely for the addressee. If you received this in error, please contact the sender and delete the material from any computer. ---------------------------(end of broadcast)--------------------------- TIP 6: explain analyze is your friend
