Frank van Vugt <[EMAIL PROTECTED]> writes:
> If I ditch the group by, then this contraint does get pushed into the
> subselect :
You're misinterpreting it. Without the group by, the plan is a
candidate for nestloop-with-inner-index-scan; with the group by,
there's another step in the way.
Pushing down into subselects does get done, for instance in CVS tip
I can change the last part of your query to "foo.article_id < 50"
and get
Hash Join (cost=25.18..53.53 rows=335 width=8)
Hash Cond: ("outer".id = "inner".article_id)
-> Seq Scan on article (cost=0.00..20.00 rows=1000 width=4)
-> Hash (cost=25.01..25.01 rows=67 width=8)
-> Subquery Scan foo (cost=24.17..25.01 rows=67 width=8)
-> HashAggregate (cost=24.17..24.34 rows=67 width=8)
-> Seq Scan on package (cost=0.00..22.50 rows=334 width=8)
Filter: (article_id < 50)
Obviously this is on toy tables, but the point is that the constraint
does get pushed down through the GROUP BY when appropriate.
regards, tom lane
---------------------------(end of broadcast)---------------------------
TIP 8: explain analyze is your friend
