Outer where pushed down

Hi all,

consider this view:

CREATE OR REPLACE VIEW v_current_connection AS
SELECT ul.id_user
FROM   user_login ul,      current_connection cc
WHERE ul.id_user = cc.id_user;


And this is the explain on a usage of that view:

# explain select * from v_current_connection_test where sp_connected_test(id_user) = FALSE;
                 QUERY PLAN
 
----------------------------------------------------------------------------------------------------------Hash Join
(cost=42.79..1325.14rows=451 width=5)  Hash Cond: ("outer".id_user = "inner".id_user)  ->  Seq Scan on user_login ul
(cost=0.00..1142.72rows=27024 width=4)        Filter: (sp_connected_test(id_user) = false)  ->  Hash
(cost=40.49..40.49rows=919 width=5)        ->  Index Scan using idx_connected on current_connection cc
(cost=0.00..40.49rows=919 width=5)              Index Cond: (connected = true)
 
(7 rows)

apart my initial surprise to see that function applied at rows not returned by the view
( Tom Lane explained me that the planner is able to push down the outer condition )
why postgres doesn't apply that function at table current_connection given the fact are extimated
only 919 vs 27024 rows?


redefining the view:

CREATE OR REPLACE VIEW v_current_connection AS
SELECT cc.id_user
FROM   user_login ul,      current_connection cc
WHERE ul.id_user = cc.id_user;

then I obtain the "desidered" plan.


# explain select * from v_current_connection_test where sp_connected_test(id_user ) = FALSE;
                  QUERY PLAN
 
----------------------------------------------------------------------------------------------------------Hash Join
(cost=46.23..1193.47rows=452 width=5)  Hash Cond: ("outer".id_user = "inner".id_user)  ->  Seq Scan on user_login ul
(cost=0.00..872.48rows=54048 width=4)  ->  Hash  (cost=45.08..45.08 rows=460 width=5)        ->  Index Scan using
idx_connectedon current_connection cc  (cost=0.00..45.08 rows=460 width=5)              Index Cond: (connected = true)
           Filter: (sp_connected_test(id_user) = false)
 
(7 rows)



Is not possible in any way push postgres to apply that function to the right table ?
Shall I rewrite the views figuring out wich column is better to expose ?



Regards
Gaetano Mendola