Re: Slow performance with no apparent reason

I guess my first message was not accurate, since t1 is a view, that
includes t2.

Attached are the real queries with their corresponding plans, the first
one takes 10.8 sec to execute, the second one takes 0.6 sec.

To simplify, I expanded the view, so the attached query refers to tables
only.

Martijn van Oosterhout wrote:

>Please supply EXPLAIN ANALYZE output.
>
>On Sun, Oct 26, 2003 at 12:25:37AM +0300, Yonatan Goraly wrote:
>
>
>>I am in the process of adding PostgreSQL support for an application, in
>>addition to Oracle and MS SQL.
>>I am using PostgreSQL version 7.3.2, Red Hat 9.0 on Intel Pentium III board.
>>
>>I have a query that generally looks like this:
>>
>>SELECT t1.col1, t2.col1 FROM t1, t2 WHERE t1.x=t2.y AND t2.p='string'
>>AND t2.q=1
>>
>>This query is strikingly slow (about 100 sec when both t1 and t2 has
>>about 1,200 records, compare with less than 4 sec with MS SQL and Oracle)
>>
>>The strange thing is that if I remove one of the last 2 conditions
>>(doesn't matter which one), I get the same performance like with the
>>other databases.
>>Since in this particular case both conditions ( t2.p='string', t2.q=1)
>>are not required, I can't understand why having both turns the query so
>>slow.
>>A query on table t2 alone is fast with or without the 2 conditions.
>>
>>I tired several alternatives, this one works pretty well:
>>
>>SELECT t1.col1, t2.col1 FROM t1, t2 WHERE t1.x=t2.y AND
>> EXISTS (
>> SELECT * FROM t2 t2a WHERE t2a.p='string' AND t2a.q=1 AND
>>t2a.y=t2.y )
>>
>>Since the first query is simpler than the second, it seems to me like a bug.
>>
>>Please advise
>>
>>Yonatan
>>
>>
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