Hi!
On Dec 12, Colin Faber wrote:
> Hi,
>
> I've got a feature request which I don't think should be all that hard
> to implement (if not already)
>
> With in the mysql fulltext search system if your search words exist in
> more than 50% of the records; it is ignored.
>
> How about having mysql return either an error or set something that can
> be retrieved which will notify if this event happens.
>
> A feature like this would allow people that use the FTS as the bases of
> a search engine to return nifty little `google like' results. "The
> following words were not included in the search because of their
> commonality with in our database .. 'words'"
>
> etc.
>
Colin, unfortunately this feature would be difficult to add.
The word that exists more than in 50% rows is not, in fact, ignored -
it does not recieve any special treatment at all.
What happens, is that word weight uses
log((total_number_of_rows-rows_matched)/rows_matched)
You see, that if rows_matched > total_number_of_rows/2, this gives
negative number and, as weight cannot be negative, is replaced by zero.
This formula was chosen from a number of different weighting schemes
in a series of tests aimed at best search effectivity.
By modifying ftdefs.h it can be replaced by a formula
that always produces positive weights, thus removing 50% limit.
Still, all this can be changed in MySQL 4.1 or 4.2
Regards,
Sergei
--
MySQL Development Team
__ ___ ___ ____ __
/ |/ /_ __/ __/ __ \/ / Sergei Golubchik <[EMAIL PROTECTED]>
/ /|_/ / // /\ \/ /_/ / /__ MySQL AB, http://www.mysql.com/
/_/ /_/\_, /___/\___\_\___/ Osnabrueck, Germany
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