Mroonga Overview
Contents
Once Mroonga has been installed (see About Mroonga), its basic usage is similar to that of a regular fulltext index.
For example:
CREATE TABLE ft_mroonga(copy TEXT,FULLTEXT(copy)) ENGINE=Mroonga;
INSERT INTO ft_mroonga(copy) VALUES ('Once upon a time'),
('There was a wicked witch'), ('Who ate everybody up');
SELECT * FROM ft_mroonga WHERE MATCH(copy) AGAINST('wicked');
+--------------------------+
| copy |
+--------------------------+
| There was a wicked witch |
+--------------------------+
Score
Mroonga can also order by weighting. For example, first add another record:
INSERT INTO ft_mroonga(copy) VALUES ('She met a wicked, wicked witch');
Records can be returned by weighting, for example, the newly added record has two occurences of the word 'wicked' and a higher weighting:
SELECT *, MATCH(copy) AGAINST('wicked') AS score FROM ft_mroonga
WHERE MATCH(copy) AGAINST('wicked') ORDER BY score DESC;
+--------------------------------+--------+
| copy | score |
+--------------------------------+--------+
| She met a wicked, wicked witch | 299594 |
| There was a wicked witch | 149797 |
+--------------------------------+--------+
Parser
Mroonga permits you to set a different parser for searching by specifying the parser in the CREATE TABLE statement as a comment or, in older versions, changing the value of the mroonga_default_parser system variable.
For example:
CREATE TABLE ft_mroonga(copy TEXT,FULLTEXT(copy) COMMENT 'parser "TokenDelimitNull"') ENGINE=Mroonga;,
or
SET GLOBAL mroonga_default_parser = 'TokenBigramSplitSymbol';
The following parser settings are available:
| Setting | Description |
|---|---|
| off | No tokenizing is performed. |
| TokenBigram | Default value. Continuous alphabetical characters, numbers or symbols are treated as a token. |
| TokenBigramIgnoreBlank | Same as TokenBigram except that white spaces are ignored. |
| TokenBigramIgnoreBlankSplitSymbol | Same as TokenBigramSplitSymbol. except that white spaces are ignore. |
| TokenBigramIgnoreBlankSplitSymbolAlpha | Same as TokenBigramSplitSymbolAlpha except that white spaces are ignored. |
| TokenBigramIgnoreBlankSplitSymbolAlphaDigit | Same as TokenBigramSplitSymbolAlphaDigit except that white spaces are ignored. |
| TokenBigramSplitSymbol | Same as TokenBigram except that continuous symbols are not treated as a token, but tokenised in bigram. |
| TokenBigramSplitSymbolAlpha | Same as TokenBigram except that continuous alphabetical characters are not treated as a token, but tokenised in bigram. |
| TokenDelimit | Tokenises by splitting on white spaces. |
| TokenDelimitNull | Tokenises by splitting on null characters (\0). |
| TokenMecab | Tokenise using MeCab. Required Groonga to be buillt with MeCab support. |
| TokenTrigram | Tokenises in trigrams but continuous alphabetical characters, numbers or symbols are treated as a token. |
| TokenUnigram | Tokenises in unigrams but continuous alphabetical characters, numbers or symbols are treated as a token. |
Examples
TokenBigram vs TokenBigramSplitSymbol
TokenBigram failing to match partial symbols which TokenBigramSplitSymbol matches, since TokenBigramSplitSymbol does not treat continuous symbols as a token.
DROP TABLE ft_mroonga;
CREATE TABLE ft_mroonga(copy TEXT,FULLTEXT(copy) COMMENT 'parser "TokenBigram"')
ENGINE=Mroonga;
INSERT INTO ft_mroonga(copy) VALUES ('Once upon a time'),
('There was a wicked witch'),
('Who ate everybody up'),
('She met a wicked, wicked witch'),
('A really wicked, wicked witch!!?!');
SELECT * FROM ft_mroonga WHERE MATCH(copy) AGAINST('!?');
Empty set (0.00 sec)
DROP TABLE ft_mroonga;
CREATE TABLE ft_mroonga(copy TEXT,FULLTEXT(copy) COMMENT 'parser "TokenBigramSplitSymbol"')
ENGINE=Mroonga;
INSERT INTO ft_mroonga(copy) VALUES ('Once upon a time'),
('There was a wicked witch'),
('Who ate everybody up'),
('She met a wicked, wicked witch'),
('A really wicked, wicked witch!!?!');
SELECT * FROM ft_mroonga WHERE MATCH(copy) AGAINST('!?');
+-----------------------------------+
| copy |
+-----------------------------------+
| A really wicked, wicked witch!!?! |
+-----------------------------------+
TokenBigram vs TokenBigramSplitSymbolAlpha
DROP TABLE ft_mroonga;
CREATE TABLE ft_mroonga(copy TEXT,FULLTEXT(copy) COMMENT 'parser "TokenBigram"')
ENGINE=Mroonga;
INSERT INTO ft_mroonga(copy) VALUES ('Once upon a time'),
('There was a wicked witch'),
('Who ate everybody up'),
('She met a wicked, wicked witch'),
('A really wicked, wicked witch!!?!');
SELECT * FROM ft_mroonga WHERE MATCH(copy) AGAINST('ick');
Empty set (0.00 sec)
DROP TABLE ft_mroonga;
CREATE TABLE ft_mroonga(copy TEXT,FULLTEXT(copy) COMMENT 'parser "TokenBigramSplitSymbolAlpha"')
ENGINE=Mroonga;
INSERT INTO ft_mroonga(copy) VALUES ('Once upon a time'),
('There was a wicked witch'),
('Who ate everybody up'),
('She met a wicked, wicked witch'),
('A really wicked, wicked witch!!?!');
SELECT * FROM ft_mroonga WHERE MATCH(copy) AGAINST('ick');
+-----------------------------------+
| copy |
+-----------------------------------+
| There was a wicked witch |
| She met a wicked, wicked witch |
| A really wicked, wicked witch!!?! |
+-----------------------------------+
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