Re: Optimizer hook - Mailing list pgsql-patches

From Julius Stroffek
Subject Re: Optimizer hook
Date
Msg-id 46F99C70.50203@sun.com
Whole thread Raw
In response to Re: Optimizer hook  (Tom Lane <tgl@sss.pgh.pa.us>)
Responses Re: Optimizer hook  (Tom Lane <tgl@sss.pgh.pa.us>)
Re: Optimizer hook  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-patches
> Why would you care?  Seems like forcing that to not happen is actively
> making it stupider.
>
To better compare the algorithms and possibly not for final solution at
the beginning. If we would implement 10 algorithms and want to pickup
just 3 best ones to be used and throw 7 away.

Later on, we can try to run just the one "very fast" algorithm and
depending on the cost decide whether we would run remaining 9 or
less or even none.

Yes, the example in dummy.c is really stupider, but it could be done
in more clever way.

> Well, I can see one likely problem: list_copy is a shallow copy and
> thus doesn't ensure that the second set of functions sees the same input
> data structures as the first.  I know that geqo has to go through some
> special pushups to perform multiple invocations of the base planner,
> and I suspect you need that here too.  Look at geqo_eval().

I'll explore that.

Thanks

Regards

Julius Stroffek


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