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MATCH ... AGINST (... IN BOOLEAN MODE) documented

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