| From: | David G Johnston <david(dot)g(dot)johnston(at)gmail(dot)com> |
|---|---|
| To: | pgsql-general(at)postgresql(dot)org |
| Subject: | Re: Optimizer issue -- bad query plan? |
| Date: | 2014-06-05 22:38:31 |
| Message-ID: | 1402007911350-5806264.post@n5.nabble.com |
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| Lists: | pgsql-general |
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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