Indeed. I tried it in 7.2.4 on a couple of empty tables, and it does do the right thing...
Also, I have another copy (not exact copy, but identical schema, and similar content... but about twice smaller) of the original database... I tried my query on it, and it works right too.
So, there must be something wrong with that particular database I suppose...
Any ideas what I should look at?
Thanks a lot!
Dima
Tom Lane wrote:
Dmitry Tkach <[EMAIL PROTECTED]> writes:
The query plan looks identical in both cases:
Limit (cost=0.00..12.51 rows=1 width=8)
-> Nested Loop (cost=0.00..1009772807.91 rows=80740598 width=8)
-> Index Scan using b_pkey on b (cost=0.00..375410773.29 rows=80740598 width=4)
-> Index Scan using a_pkey on a (cost=0.00..6.85 rows=1 width=4)
... which makes me think that it decides to use b as the outer table for both cases (which would obviously make it suck in the first one)... :-(
That's what it says, all right, which seems odd to me. Are you sure you looked at the right plans?
This happens on 7.2.4... I have a 7.3 database with the same schema, but it is not populated with data, so I could not test it on 7.3...
I could not reproduce a problem on 7.2.4. I get (using toy tables, and suppressing the planner's urge to use mergejoin instead)
lo=# explain select * from a, b where a.id >= 7901288 and a.id=b.id limit 1; NOTICE: QUERY PLAN:
Limit (cost=0.00..4.97 rows=1 width=8) -> Nested Loop (cost=0.00..1657.34 rows=333 width=8) -> Index Scan using a_pkey on a (cost=0.00..45.50 rows=333 width=4) -> Index Scan using b_pkey on b (cost=0.00..4.82 rows=1 width=4)
EXPLAIN lo=# explain select * from a, b where b.id >= 7901288 and a.id=b.id limit 1; NOTICE: QUERY PLAN:
Limit (cost=0.00..4.97 rows=1 width=8) -> Nested Loop (cost=0.00..1657.34 rows=333 width=8) -> Index Scan using b_pkey on b (cost=0.00..45.50 rows=333 width=4) -> Index Scan using a_pkey on a (cost=0.00..4.82 rows=1 width=4)
EXPLAIN
which looks like the right thing.
regards, tom lane
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