Re: Optimizer issue -- bad query plan?

Moshe Jacobson wrote
> I have the following query:
> [...]
> The EXPLAIN ANALYZE for this query indicates that all of the tables in the
> query are being joined despite the fact that they are not needed at all.
>
> Why is this?

Without definitions of all the tables involved, as well as knowing what
version you are running this query on, it is impossible to explain why.

https://wiki.postgresql.org/wiki/What's_new_in_PostgreSQL_9.0

Read the section named "Join Removal".

It would seem that in theory at least some of these could be removed -
though maybe not all of them - if you are running 9.0+ (possibly after some
schema changes).

David J.




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