Hello,
According to the documentation, I thought it was possible to force given
join orders with parenthesis.
But in this small example, this seems to have no effect;
With the first query, I'd expected to see t3 in the Merge Right Join
but both queries return the same query plan .
I'm missing a point ?
(Postgres 8.3)
create temp table t1(i int);
create temp table t2(i int);
create temp table t3(i int);
select * from ( ( t1 LEFT OUTER JOIN t2 on (t1.i=t2.i) ) LEFT OUTER JOIN t3 on (t2.i=t3.i))
select * from ( t1 LEFT OUTER JOIN (t2 LEFT OUTER JOIN t3 on (t2.i=t3.i) ) on (t1.i=t2.i)
)
Merge Right Join (cost=506.24..6206.24 rows=345600 width=12) Merge Cond: (t2.i = t1.i) -> Merge Left Join
(cost=337.49..781.49rows=28800 width=8) Merge Cond: (t2.i = t3.i) -> Sort (cost=168.75..174.75 rows=2400
width=4) Sort Key: t2.i -> Seq Scan on t2 (cost=0.00..34.00 rows=2400 width=4) -> Sort
(cost=168.75..174.75rows=2400 width=4) Sort Key: t3.i -> Seq Scan on t3 (cost=0.00..34.00
rows=2400width=4) -> Sort (cost=168.75..174.75 rows=2400 width=4) Sort Key: t1.i -> Seq Scan on t1
(cost=0.00..34.00rows=2400 width=4)
best regards,
Marc Mamin
