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..781.49 rows=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..174.75 rows=2400 width=4)
Sort Key: t3.i
-> Seq Scan on t3 (cost=0.00..34.00 rows=2400 width=4)
-> Sort (cost=168.75..174.75 rows=2400 width=4)
Sort Key: t1.i
-> Seq Scan on t1 (cost=0.00..34.00 rows=2400 width=4)
best regards,
Marc Mamin
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