要索引的单词的最小长度和最大长度由 innodb_ft_min_token_size 和 innodb_ft_max_token_size 定义用于 InnoDB 搜索索引，而 ft_min_word_len 和 ft_max_word_len 则用于 MyISAM 索引。The minimum and maximum lengths of words to be indexed are defined by the innodb_ft_min_token_size and innodb_ft_max_token_size for InnoDB search indexes, and ft_min_word_len and ft_max_word_len for MyISAM ones.

更改这些选项中的任何一个后，需要重建您的 FULLTEXT 索引以使更改生效。例如，要使两字符的单词可搜索，可以将以下行放入选项文件中：After changing any of these options, rebuild your FULLTEXT indexes for the change to take effect. For example, to make two-character words searchable, you could put the following lines in an option file:

[mysqld]
innodb_ft_min_token_size=2
ft_min_word_len=2

然后重启服务器并重建你的 FULLTEXT 索引。对于 MyISAM 表，请注意在下面关于 myisamchk 的说明中关于重建 MyISAM 全文索引的备注。Then restart the server and rebuild your FULLTEXT indexes. For MyISAM tables, note the remarks regarding myisamchk in the instructions that follow for rebuilding MyISAM full-text indexes.

对于 MyISAM 搜索索引，自然语言搜索的 50% 阈值是由所选的特定加权方案决定的。要禁用它，请在 storage/myisam/ftdefs.h 中查找以下行：For MyISAM search indexes, the 50% threshold for natural language searches is determined by the particular weighting scheme chosen. To disable it, look for the following line in storage/myisam/ftdefs.h:

#define GWS_IN_USE GWS_PROB

将那一行改成这个：Change that line to this:

#define GWS_IN_USE GWS_FREQ

然后重新编译 MySQL。在这种情况下无需重建索引。Then recompile MySQL. There is no need to rebuild the indexes in this case.

要更改用于MyISAM表的布尔全文搜索的运算符，请设置ft_boolean_syntax系统变量。（InnoDB没有相应的设置。）此变量可以在服务器运行时更改，但您必须拥有设置全局系统变量的足够权限（参见第 7.1.9.1 节，“系统变量权限”）。在这种情况下无需重建索引。To change the operators used for boolean full-text searches on MyISAM tables, set the ft_boolean_syntax system variable. (InnoDB does not have an equivalent setting.) This variable can be changed while the server is running, but you must have privileges sufficient to set global system variables (see Section 7.1.9.1, “System Variable Privileges”). No rebuilding of indexes is necessary in this case.

对于内置的全文解析器，你可以通过几种方式更改被视为单词字符的字符集，如下列清单所述。修改后，需要重新构建包含任何 FULLTEXT 索引的每个表的索引。假设你想将连字符（'-'）视为单词字符，请使用以下方法之一：For the built-in full-text parser, you can change the set of characters that are considered word characters in several ways, as described in the following list. After making the modification, rebuild the indexes for each table that contains any FULLTEXT indexes. Suppose that you want to treat the hyphen character ('-') as a word character. Use one of these methods:

要使更改生效，在修改以下任何全文索引变量后，必须重建 FULLTEXT 索引：innodb_ft_min_token_size；innodb_ft_max_token_size；innodb_ft_server_stopword_table；innodb_ft_user_stopword_table；innodb_ft_enable_stopword；ngram_token_size。修改 innodb_ft_min_token_size、innodb_ft_max_token_size 或 ngram_token_size 需要重启服务器。For the changes to take effect, FULLTEXT indexes must be rebuilt after modifying any of the following full-text index variables: innodb_ft_min_token_size; innodb_ft_max_token_size; innodb_ft_server_stopword_table; innodb_ft_user_stopword_table; innodb_ft_enable_stopword; ngram_token_size. Modifying innodb_ft_min_token_size, innodb_ft_max_token_size, or ngram_token_size requires restarting the server.

要重建 FULLTEXT 索引的 InnoDB 表，请使用带有 DROP INDEX 和 ADD INDEX 选项的 ALTER TABLE 来删除并重新创建每个索引。To rebuild FULLTEXT indexes for an InnoDB table, use ALTER TABLE with the DROP INDEX and ADD INDEX options to drop and re-create each index.

在具有全文索引的表上运行 OPTIMIZE TABLE 会重建全文索引，移除已删除的文档 ID，并尽可能合并同一单词的多个条目。Running OPTIMIZE TABLE on a table with a full-text index rebuilds the full-text index, removing deleted Document IDs and consolidating multiple entries for the same word, where possible.

要优化全文本索引，请启用 innodb_optimize_fulltext_only 并运行 OPTIMIZE TABLE。To optimize a full-text index, enable innodb_optimize_fulltext_only and run OPTIMIZE TABLE.

mysql> set GLOBAL innodb_optimize_fulltext_only=ON;
Query OK, 0 rows affected (0.01 sec)

mysql> OPTIMIZE TABLE opening_lines;
+--------------------+----------+----------+----------+
| Table              | Op       | Msg_type | Msg_text |
+--------------------+----------+----------+----------+
| test.opening_lines | optimize | status   | OK       |
+--------------------+----------+----------+----------+
1 row in set (0.01 sec)    

为了避免在大表上对全文索引进行完全重建时耗时过长，可以使用 innodb_ft_num_word_optimize 选项分阶段执行优化。innodb_ft_num_word_optimize 选项定义了每次运行 OPTIMIZE TABLE 时优化的单词数量。默认设置为 2000，这意味着每次运行 OPTIMIZE TABLE 时会优化 2000 个单词。后续的 OPTIMIZE TABLE 操作会从前一次 OPTIMIZE TABLE 操作结束的地方继续执行。To avoid lengthy rebuild times for full-text indexes on large tables, you can use the innodb_ft_num_word_optimize option to perform the optimization in stages. The innodb_ft_num_word_optimize option defines the number of words that are optimized each time OPTIMIZE TABLE is run. The default setting is 2000, which means that 2000 words are optimized each time OPTIMIZE TABLE is run. Subsequent OPTIMIZE TABLE operations continue from where the preceding OPTIMIZE TABLE operation ended.

如果你修改影响索引的全文变量（ft_min_word_len、ft_max_word_len 或 ft_stopword_file），或者如果你更改了停止词文件本身，那么在修改并重启服务器后，必须重建你的 FULLTEXT 索引。If you modify full-text variables that affect indexing (ft_min_word_len, ft_max_word_len, or ft_stopword_file), or if you change the stopword file itself, you must rebuild your FULLTEXT indexes after making the changes and restarting the server.

要为 MyISAM 表重建 FULLTEXT 索引，仅需执行一次 QUICK 修复操作即可：To rebuild the FULLTEXT indexes for a MyISAM table, it is sufficient to do a QUICK repair operation:

mysql> REPAIR TABLE tbl_name QUICK;

或者，如上所述使用 ALTER TABLE。在某些情况下，这可能比修复操作更快。Alternatively, use ALTER TABLE as just described. In some cases, this may be faster than a repair operation.

每个包含任何 FULLTEXT 索引的表都必须按照上述方法进行修复。否则，对表的查询可能会产生不正确的结果，并且对表的修改会导致服务器认为该表已损坏，需要修复。Each table that contains any FULLTEXT index must be repaired as just shown. Otherwise, queries for the table may yield incorrect results, and modifications to the table causes the server to see the table as corrupt and in need of repair.

If you use myisamchk to perform an operation that modifies MyISAM table indexes (such as repair or analyze), the FULLTEXT indexes are rebuilt using the 默认 full-text parameter values for minimum word length, maximum word length, and stopword file unless you specify otherwise. This can result in queries failing.If you use myisamchk to perform an operation that modifies MyISAM table indexes (such as repair or analyze), the FULLTEXT indexes are rebuilt using the default full-text parameter values for minimum word length, maximum word length, and stopword file unless you specify otherwise. This can result in queries failing.

这个问题的发生是因为这些参数只有服务器知道。它们没有存储在MyISAM索引文件中。为了避免这个问题，如果你修改了服务器使用的最小或最大词长或停用词文件值，请为你用于myisamchk的mysqld指定相同的ft_min_word_len、ft_max_word_len和ft_stopword_file值。例如，如果你将最小词长设置为 3，你可以这样使用myisamchk来修复表：The problem occurs because these parameters are known only by the server. They are not stored in MyISAM index files. To avoid the problem if you have modified the minimum or maximum word length or stopword file values used by the server, specify the same ft_min_word_len, ft_max_word_len, and ft_stopword_file values for myisamchk that you use for mysqld. For example, if you have set the minimum word length to 3, you can repair a table with myisamchk like this:

myisamchk --recover --ft_min_word_len=3 tbl_name.MYI

为了确保 myisamchk 和服务器使用相同的全文本参数值，请将每个参数同时放在选项文件的 [mysqld] 和 [myisamchk] 部分：To ensure that myisamchk and the server use the same values for full-text parameters, place each one in both the [mysqld] and [myisamchk] sections of an option file:

[mysqld]
ft_min_word_len=3

[myisamchk]
ft_min_word_len=3

使用myisamchk for MyISAM table index modification is to use the REPAIR TABLE, ANALYZE TABLE, OPTIMIZE TABLE，或ALTER TABLE statements. These statements are performed by the server, which knows the proper full-text parameter values to use.An alternative to using myisamchk for MyISAM table index modification is to use the REPAIR TABLE, ANALYZE TABLE, OPTIMIZE TABLE, or ALTER TABLE statements. These statements are performed by the server, which knows the proper full-text parameter values to use.