Re: optimization for repeated values within JOINs

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04-15-2008, 11:02 PM

Oliver Jowett

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Re: optimization for repeated values within JOINs

Bill Schneider wrote:

> Does the PostgreSQL JDBC driver/protocol perform any optimization for
> repeated values created by joins?

No. The existing protocol is documented at
http://www.postgresql.org/docs/8.0/static/protocol.html

> Has anyone else thought about this, or does it just not affect
> performance enough to matter?

pgsql-hackers is probably the place to discuss it.

> select a.id, a.longText, b.id
> from a join b on b.a_id = a.id
> order by a.id;

In this case, you could of course turn it into two separate queries when
you know the characteristics of the query make that a win. It seems like
a lot of work for marginal benefit to try to do some sort of
duplicate-elimination automatically in the protocol.

-O

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Re: optimization for repeated values within JOINs