Subject | Re[2]: [ib-support] Optimizer or De-optimizer ? |
---|---|
Author | Ann W. Harrison |
Post date | 2001-03-21T21:56:56Z |
At 03:29 PM 3/21/2001 -0300, Carlos H. Cantu wrote:
performing lookups in the larger. Every hit in the larger table
will be a result. Remember that a foreign key column can be
null, so the larger table might have lots of rows that have
no match in the smaller table.
the right plan now and a different plan, also right, under different
conditions. A plan you attach to the query eliminates that possibility.
Regards,
Ann
www.ibphoenix.com
We have answers.
>Aquisi is the larger table. I tried to put the lookup field as part of theI think the optimization is correct. Walk the smaller table,
>Query but it didnt change the plan.
performing lookups in the larger. Every hit in the larger table
will be a result. Remember that a foreign key column can be
null, so the larger table might have lots of rows that have
no match in the smaller table.
>If I understand correctly, the PLAN can change when the tables grow up, soIt is (theoretically) more likely that the optimizer will choose
>the right PLAN today can be the wrong PLAN tomorrow, right ?
the right plan now and a different plan, also right, under different
conditions. A plan you attach to the query eliminates that possibility.
Regards,
Ann
www.ibphoenix.com
We have answers.