On 07/10/2013 09:18 AM, Atri Sharma wrote:
>> Can you please post an example of such a join removal? I mean a query before
>> and after the removal. Thanks,
> Courtesy Robert Haas:
>
> SELECT foo.x, foo.y, foo.z FROM foo WHERE foo.x = bar.x
>
> Conditions:
>
> 1) foo.x is not null.
I guess that this is also not needed. you can just remove rows where
foo.x is null
That is, replace the join with "foo.x is not null"
>
> 2) foo (x) is a foreign key referencing bar (x).
>
> We can ignore bar completely in this case i.e. avoid scanning bar.
>
> Regards,
>
> Atri
>
>
> --
> Regards,
>
> Atri
> l'apprenant
>
>
--
Hannu Krosing
PostgreSQL Consultant
Performance, Scalability and High Availability
2ndQuadrant Nordic OÜ
