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MATCH ... AGINST (... IN BOOLEAN MODE) documented
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173
Docs/manual.texi
173
Docs/manual.texi
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@ -3691,7 +3691,7 @@ Allow users to change startup options without taking down the server.
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Fail safe replication.
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@item
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More functions for full-text search.
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@xref{Fulltext Features in MySQL 4.0}.
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@xref{Fulltext TODO}.
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@item
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New key cache
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@item
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@ -18044,6 +18044,7 @@ differ somewhat:
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| ft_min_word_len | 4 |
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| ft_max_word_len | 254 |
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| ft_max_word_len_for_sort | 20 |
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| ft_boolean_syntax | + -><()~* |
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| have_bdb | YES |
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| have_innodb | YES |
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| have_raid | YES |
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@ -18250,6 +18251,9 @@ lot of words into index the slow way - but short words will be inserted very
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fast. It applies only to index recreation during @code{REPAIR},
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@code{CREATE INDEX}, or @code{ALTER TABLE}.
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@item @code{ft_boolean_syntax}
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List of operators supported by @code{MATCH ... AGAINST(... IN BOOLEAN MODE)}.
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@xref{Fulltext Search}.
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@item @code{have_innodb}
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@code{YES} if @code{mysqld} supports InnoDB tables. @code{DISABLED}
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@ -29156,18 +29160,18 @@ mysql> select STRCMP('text', 'text');
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@findex MATCH ... AGAINST()
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@item MATCH (col1,col2,...) AGAINST (expr)
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@itemx MATCH (col1,col2,...) AGAINST (expr IN BOOLEAN MODE)
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@code{MATCH ... AGAINST()} is used for full-text search and returns
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relevance - similarity measure between the text in columns
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@code{(col1,col2,...)} and the query @code{expr}. Relevance is a
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positive floating-point number. Zero relevance means no similarity.
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For @code{MATCH ... AGAINST()} to work, a @strong{FULLTEXT} index
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must be created first. @xref{CREATE TABLE, , @code{CREATE TABLE}}.
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@code{MATCH ... AGAINST()} is available in MySQL Version
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3.23.23 or later. For details and usage examples
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@pxref{Fulltext Search}.
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@code{MATCH ... AGAINST()} is available in MySQL version
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3.23.23 or later. @code{IN BOOLEAN MODE} extension was added in version
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4.0.1. For details and usage examples @pxref{Fulltext Search}.
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@end table
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@node Case Sensitivity Operators, , String comparison functions, String functions
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@subsubsection Case Sensitivity
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@ -33679,9 +33683,9 @@ and searching. Full-text indexes in MySQL are an index of type
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@code{FULLTEXT}. @code{FULLTEXT} indexes can be created from @code{VARCHAR}
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and @code{TEXT} columns at @code{CREATE TABLE} time or added later with
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@code{ALTER TABLE} or @code{CREATE INDEX}. For large datasets, adding
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@code{FULLTEXT} index with @code{ALTER TABLE} (or @code{CREATE INDEX}) would
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be much faster than inserting rows into the empty table with a @code{FULLTEXT}
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index.
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@code{FULLTEXT} index with @code{ALTER TABLE} (or @code{CREATE INDEX})
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would be much faster than inserting rows into the empty table that has
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a @code{FULLTEXT} index.
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Full-text search is performed with the @code{MATCH} function.
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@ -33714,7 +33718,8 @@ mysql> SELECT * FROM articles WHERE MATCH (title,body) AGAINST ('database');
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2 rows in set (0.00 sec)
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@end example
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The function @code{MATCH} matches a natural language query @code{AGAINST}
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The function @code{MATCH} matches a natural language (or boolean,
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see below) query in case-insensitive fashion @code{AGAINST}
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a text collection (which is simply the set of columns covered by a
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@code{FULLTEXT} index). For every row in a table it returns relevance -
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a similarity measure between the text in that row (in the columns that are
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@ -33730,7 +33735,7 @@ The above is a basic example of using @code{MATCH} function. Rows are
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returned with relevance decreasing.
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@example
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mysql> SELECT id,MATCH (title,body) AGAINST ('Tutorial') FROM articles;
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mysql> SELECT id,MATCH title,body AGAINST ('Tutorial') FROM articles;
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+----+-----------------------------------------+
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| id | MATCH (title,body) AGAINST ('Tutorial') |
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+----+-----------------------------------------+
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@ -33748,7 +33753,7 @@ This example shows how to retrieve the relevances. As neither @code{WHERE}
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nor @code{ORDER BY} clauses are present, returned rows are not ordered.
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@example
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mysql> SELECT id, body, MATCH (title,body) AGAINST (
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mysql> SELECT id, body, MATCH title,body AGAINST (
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-> 'Security implications of running MySQL as root') AS score
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-> FROM articles WHERE MATCH (title,body) AGAINST
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-> ('Security implications of running MySQL as root');
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@ -33802,27 +33807,98 @@ We all know this happens far too often when we are trying to find something on
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the Internet with a search engine. It is with this reasoning that such rows
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have been assigned a low semantical value in @strong{this particular dataset}.
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Since version 4.0.1 MySQL can also perform boolean fulltext searches using
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@code{IN BOOLEAN MODE} modifier.
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@example
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mysql> SELECT * FROM articles WHERE MATCH (title,body) AGAINST (
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-> '+MySQL -YourSQL' IN BOOLEAN MODE);
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+----+------------------------------+-----------------------------------------------+
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| id | title | body |
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+----+------------------------------+-----------------------------------------------+
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| 1 | MySQL Tutorial | DBMS stands for DataBase Management ... |
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| 2 | How To Use MySQL Efficiently | After you went through a ... |
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| 3 | Optimising MySQL | In this tutorial we will show how to ... |
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| 4 | 1001 MySQL Trick | 1. Never run mysqld as root. 2. Normalise ... |
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| 6 | MySQL Security | When configured properly, MySQL could be ... |
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+----+------------------------------+-----------------------------------------------+
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@end example
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This query retrieved all the rows that contain the word @code{MySQL}
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(note: 50% threshold is gone), but does @strong{not} contain the word
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@code{YourSQL}. Note that it does not auto-magically sort rows in
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derceasing relevance order (the last row has the highest relevance,
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as it contains @code{MySQL} twice).
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Boolean fulltext search supports the following operators:
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@table @code
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@item +
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A plus sign prepended to a word indicates that this word @strong{must be}
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present in every row returned.
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@item -
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A minus sign prepended to a word indicates that this word @strong{must not}
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be present in the rows returned.
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@item
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By default - without plus or minus - the word is optional, but the rows that
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contain it will be rated higher. This mimicks the behaviour of
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@code{MATCH ... AGAINST()} without @code{IN BOOLEAN MODE} modifier.
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@item < >
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These two operators are used to increase and decrease word's contribution
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to the relevance value, assigned to a row. See an example below.
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@item ( )
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Parentheses are used - as usual - to group words into subexpressions.
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@item ~
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This is negation operator. It makes word's contribution to the row
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relevance negative. It's useful for marking noise words. A row that has
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such a word will be rated lower than others, but will not be excluded
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altogether, as with @code{-} operator.
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@item *
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This is truncation operator. Unlike others it should be @strong{appended}
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to the word, not prepended.
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@end table
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And here are some examples:
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@table @code
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@item ``apple banana''
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find rows that contain at least one of these words.
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@item ``+apple +juice''
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... both words
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@item ``+apple macintosh''
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... word ``apple'', but rank it higher if it also contain ``macintosh''
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@item ``+apple -macintosh''
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... word ``apple'' but not ``macintosh''
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@item ``+gates +(>hell <bill)''
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... ``hell'' and ``gates'', or ``bill'' and ``gates'' (in any
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order), but rank ``gates to hell'' higher than ``bill gates''.
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@item ``apple*''
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... ``apple'', ``apples'', ``applesause'', and ``applet''
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@end table
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@menu
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* Fulltext restrictions:: Fulltext restrictions
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* Fulltext Restrictions:: Fulltext Restrictions
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* Fulltext Fine-tuning:: Fine-tuning MySQL Full-text Search
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* Fulltext Features in MySQL 4.0:: New Features of Full-text Search in MySQL 4.0
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* Fulltext TODO:: Full-text Search TODO
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@end menu
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@node Fulltext restrictions, Fulltext Fine-tuning, Fulltext Search, Fulltext Search
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@subsection Fulltext restrictions
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@node Fulltext Restrictions, Fulltext Fine-tuning, Fulltext Search, Fulltext Search
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@subsection Fulltext Restrictions
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@itemize @bullet
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@item
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All parameters to the @code{MATCH} function must be columns from the
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same table that is part of the same fulltext index.
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@item
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Column list between @code{MATCH} and @code{AGAINST} must match exactly
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a column list in the @code{FULLTEXT} index definition.
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@item
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The argument to @code{AGAINST} must be a constant string.
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@end itemize
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@node Fulltext Fine-tuning, Fulltext Features in MySQL 4.0, Fulltext restrictions, Fulltext Search
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@node Fulltext Fine-tuning, Fulltext TODO, Fulltext Restrictions, Fulltext Search
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@subsection Fine-tuning MySQL Full-text Search
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Unfortunately, full-text search has few user-tunable parameters yet,
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@ -33844,13 +33920,13 @@ Change it to the value you prefer, and rebuild
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your @code{FULLTEXT} indexes.
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@item
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The stopword list is defined in @code{myisam/ft_static.c}
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The stopword list is defined in @file{myisam/ft_static.c}
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Modify it to your taste, recompile MySQL and rebuild
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your @code{FULLTEXT} indexes.
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@item
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The 50% threshold is caused by the particular weighting scheme chosen. To
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disable it, change the following line in @code{myisam/ftdefs.h}:
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disable it, change the following line in @file{myisam/ftdefs.h}:
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@example
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#define GWS_IN_USE GWS_PROB
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@end example
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@ -33860,49 +33936,22 @@ to
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@end example
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and recompile MySQL.
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There is no need to rebuild the indexes in this case.
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@strong{Note:} by doing this you @strong{severely} decrease MySQL ability
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to provide adequate relevance values by @code{MATCH} function.
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It means, that if you really need to search for such a common words,
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then you should rather search @code{IN BOOLEAN MODE}, which does not
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has 50% threshold.
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@item
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Sometimes search engine maintaner would like to change operators used
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for boolean fulltext search. They are defined by a
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@code{ft_boolean_syntax} variable. @xref{SHOW VARIABLES}.
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Still, this variable is read-only, its value is set in
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@file{myisam/ft_static.c}.
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@end itemize
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@node Fulltext Features in MySQL 4.0, Fulltext TODO, Fulltext Fine-tuning, Fulltext Search
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@subsection New Features of Full-text Search in MySQL 4.0
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This section includes a list of the fulltext features that are already
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implemented in the 4.0 tree. It explains the
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@strong{More functions for full-text search} entry of @ref{TODO MySQL 4.0}.
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@itemize @bullet
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@item @code{REPAIR TABLE} with @code{FULLTEXT} indexes,
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@code{ALTER TABLE} with @code{FULLTEXT} indexes, and
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@code{OPTIMIZE TABLE} with @code{FULLTEXT} indexes are now
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up to 100 times faster.
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@item @code{MATCH ... AGAINST} is going to supports the following
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@strong{boolean operators}:
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@itemize @bullet
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@item @code{+}word means the that word @strong{must} be present in every
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row returned.
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@item @code{-}word means the that word @strong{must not} be present in every
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row returned.
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@item @code{<} and @code{>} can be used to decrease and increase word
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weight in the query.
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@item @code{~} can be used to assign a @strong{negative} weight to a noise
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word.
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@item @code{*} is a truncation operator.
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@end itemize
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Boolean search utilises a more simplistic way of calculating the relevance,
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that does not have a 50% threshold.
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@item Searches are now up to 2 times faster due to optimised search algorithm.
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@c @item Utility program @code{ft_dump} added for low-level @code{FULLTEXT}
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@c index operations (querying/dumping/statistics).
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@end itemize
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@node Fulltext TODO, , Fulltext Features in MySQL 4.0, Fulltext Search
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@node Fulltext TODO, , Fulltext Fine-tuning, Fulltext Search
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@subsection Full-text Search TODO
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@itemize @bullet
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@ -45795,6 +45844,10 @@ Our TODO section contains what we plan to have in 4.0. @xref{TODO MySQL 4.0}.
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@itemize @bullet
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@item
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Fixed bug in @code{DELETE ... WHERE ... MATCH ...}
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@item
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Added support for @code{MATCH ... AGAINST(... IN BOOLEAN MODE)}.
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@item
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@code{LOCATE()} and @code{INSTR()} are case sensitive if neither
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argument is a binary string. binary strings.
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@item
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@ -45904,6 +45957,10 @@ Added @code{ALTER TABLE table_name DISABLE KEYS} and
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@item
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Allow one to use @code{IN} instead of @code{FROM} in @code{SHOW} commands.
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@item
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Implemented ``repair by sort'' for @code{FULLTEXT} indexes.
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@code{REPAIR TABLE}, @code{ALTER TABLE}, and @code{OPTIMIZE TABLE}
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for tables with @code{FULLTEXT} indexes are now up to 100 times faster.
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@item
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Allow ANSI SQL syntax @code{X'hexadecimal-number'}
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@item
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Cleaned up global lock handling for @code{FLUSH TABLES WITH READ LOCK}
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