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(mysql.info)Fulltext Fine-tuning

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Fine-tuning MySQL Full-text Search
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Unfortunately, full-text search has no user-tunable parameters yet,
although adding some is very high on the TODO.  However, if you have a
MySQL source distribution (Note: Installing source.), you can
somewhat alter the full-text search behavior.

Note that full-text search was carefully tuned for the best searching
effectiveness.  Modifying the default behavior will, in most cases,
only make the search results worse.  Do not alter the MySQL sources
unless you know what you are doing!

   * Minimal length of word to be indexed is defined in
     `myisam/ftdefs.h' file by the line
          #define MIN_WORD_LEN 4
     Change it to the value you prefer, recompile MySQL, and rebuild
     your `FULLTEXT' indexes.

   * The stopword list is defined in `myisam/ft_static.c' Modify it to
     your taste, recompile MySQL and rebuild your `FULLTEXT' indexes.

   * The 50% threshold is caused by the particular weighting scheme
     chosen. To disable it, change the following line in
     `myisam/ftdefs.h':
          #define GWS_IN_USE GWS_PROB
     to
          #define GWS_IN_USE GWS_FREQ
     and recompile MySQL.  There is no need to rebuild the indexes in
     this case.