InnoDB full-text search improvements¶
Ignoring stopword list¶
By default, all Full-Text Search indexes check the stopwords list, to see if any indexed elements contain words on that list.
Using this list for n-gram indexes isn’t always suitable, for example, any
item that contains a or i will be ignored. Another word that can’t be
searched is east, this one will find no matches because a is on the
FTS stopword list.
To resolve this issue, Percona Server for MySQL has the
innodb_ft_ignore_stopwords variable to control whether
InnoDB Full-Text Search should ignore the stopword list.
Although this variable is introduced to resolve n-gram issues, it affects all Full-Text Search indexes as well.
Being a stopword doesn’t just mean being one of the predefined
words from the list. Tokens shorter than innodb_ft_min_token_size
or longer than innodb_ft_max_token_size
are also considered stopwords. Therefore, when
innodb_ft_ignore_stopwords is set to ON even for non-ngram
FTS, innodb_ft_min_token_size / innodb_ft_max_token_size will be
ignored meaning that in this case very short and very long words will
also be indexed.
System variables¶
innodb_ft_ignore_stopwords¶
| Option | Description |
|---|---|
| Command-line | Yes |
| Config file | Yes |
| Scope | Session, Global |
| Dynamic | Yes |
| Data type | Boolean |
| Default | OFF |
When enabled, this variable will instruct InnoDB Full Text Search parser to ignore the stopword list when building/updating an FTS index.
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