From: | Julius Stroffek <Julius(dot)Stroffek(at)Sun(dot)COM> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-patches(at)postgresql(dot)org |
Subject: | Re: Optimizer hook |
Date: | 2007-09-25 23:40:32 |
Message-ID: | 46F99C70.50203@sun.com |
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Thread: | |
Lists: | 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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