Re: Experimental evaluation of PostgreSQL's query optimizer - Mailing list pgsql-hackers

From Tom Lane
Subject Re: Experimental evaluation of PostgreSQL's query optimizer
Date
Msg-id 21747.1450708920@sss.pgh.pa.us
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In response to Re: Experimental evaluation of PostgreSQL's query optimizer  (Viktor Leis <leis@in.tum.de>)
Responses Re: Experimental evaluation of PostgreSQL's query optimizer  (Viktor Leis <leis@in.tum.de>)
List pgsql-hackers
Viktor Leis <leis@in.tum.de> writes:
> I think it would be a good start to distinguish between nested loop
> joins with and without a index.

We do.

> In my opinion, the latter should simply NEVER be chosen.

So, if you're given a query with a non-equality join condition
that doesn't match any index on either table, you think the planner
should just fail?  This is not realistic.  Certainly nestloop with
inner seqscan is likely to be slow, but that's already reflected
in the cost estimates.
        regards, tom lane



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