Eric writes:
> Well, answering my own email, what I thought was a bug is not one at
> all. I was mistaken in thinking that MySQL paid any attention to the
> WHERE conditions when optimizing the join order beyond determining
> which keys are used for the join, correct?
>
> This is really terrible for queries like mine where the query could be
> sped up by orders of magnitude if the join optimizer would just
> determine which table in the join to scan and which to do the key
> lookup on based on a more intelligent estimation of the number of rows
> from each table. It would have to go beyond looking at what keys are
> used in the join (since each of the tables in my query can be looked
> up by the same key) and account for the WHERE conditions placed on the
> tables in the join.
>
> Is there sufficient metadata to estimate rows coming from a table
> based on conditions placed on the attributes of that table? Where is
> it? Has anyone ever thought of coding this? Can anyone give me a
> place to start?
>
> eric.
>
>
> --
> _____ _
> | ____|(_) http://ir.iit.edu/~ej
> | _| | | Page me via ICQ at
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> |______/ | or by mailing [EMAIL PROTECTED]
> |__/
>
What information do you precisely require ??
The answer also depends on the API you are using and a method of
retrieval.
For example, you can know how many rows you get if you use _store_
instead of _use_ method, but that method is not applicable in the case
of larger result sets.
--
Regards,
__ ___ ___ ____ __
/ |/ /_ __/ __/ __ \/ / Mr. Sinisa Milivojevic <[EMAIL PROTECTED]>
/ /|_/ / // /\ \/ /_/ / /__ MySQL AB, FullTime Developer
/_/ /_/\_, /___/\___\_\___/ Larnaca, Cyprus
<___/ www.mysql.com
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