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
i will be ignored. Another word that can’t be
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
innodb_ft_max_token_size will be
ignored meaning that in this case very short and very long words will
also be indexed.
When enabled, this variable will instruct InnoDB Full Text Search parser to ignore the stopword list when building/updating an FTS index.