4.4. Wrapper mode#
Here we explain how to use wrapper mode of Mroonga
4.4.1. How to use wrapper mode#
In wrapper mode, Mroonga works in wrapping an existing storage engine. To specify the wrapped storage engine, we use SQL comment like COMMENT = 'engine "InnoDB"' for now.
Note
For now, a primary key is mandatory in wrapper mode. That is not the case with storage mode.
Note
Wrapper mode supports the followings, that are not supported in storage mode for now.
null value
transaction (if storage engine supports. Note that rollback causes mismatch of indexes, it may affects search results, so recreate index of Mroonga in such a case.)
4.4.2. How to use full text search#
After confirming the installation, let’s create a table. The important point is to specify Mroonga by ENGINE = Mroonga.
mysql> CREATE TABLE diaries (
-> id INT PRIMARY KEY AUTO_INCREMENT,
-> content VARCHAR(255),
-> FULLTEXT INDEX (content)
-> ) ENGINE = Mroonga COMMENT = 'engine "InnoDB"' DEFAULT CHARSET utf8;
Query OK, 0 rows affected (0.52 sec)
We put data by INSERT.
mysql> INSERT INTO diaries (content) VALUES ("It'll be fine tomorrow.");
Query OK, 1 row affected (0.01 sec)
mysql> INSERT INTO diaries (content) VALUES ("It'll rain tomorrow");
Query OK, 1 row affected (0.00 sec)
Try full text search.
mysql> SELECT * FROM diaries WHERE MATCH(content) AGAINST("+fine" IN BOOLEAN MODE);
+----+-----------------------------------------+
| id | content |
+----+-----------------------------------------+
| 1 | It'll be fine tomorrow. |
+----+-----------------------------------------+
1 row in set (0.00 sec)
Yes, full text search works.
4.4.3. How to get search score#
We often want to display more relevant results first in full text search. We use search score in such case.
We can get search score by MySQL’s standard way [1], i.e. we use MATCH…AGAINST in one of columns in SELECT or ORDER BY.
Let’s try.
mysql> INSERT INTO diaries (content) VALUES ("It's fine today. It'll be fine tomorrow as well.");
Query OK, 1 row affected (0.00 sec)
mysql> INSERT INTO diaries (content) VALUES ("It's fine today. But it'll rain tomorrow.");
Query OK, 1 row affected (0.00 sec)
mysql> SELECT *, MATCH (content) AGAINST ("+fine" IN BOOLEAN MODE) FROM diaries WHERE MATCH (content) AGAINST ("+fine" IN BOOLEAN MODE) ORDER BY MATCH (content) AGAINST ("+fine" IN BOOLEAN MODE) DESC;
+----+--------------------------------------------------+---------------------------------------------------+
| id | content | MATCH (content) AGAINST ("+fine" IN BOOLEAN MODE) |
+----+--------------------------------------------------+---------------------------------------------------+
| 3 | It's fine today. It'll be fine tomorrow as well. | 2 |
| 1 | It'll be fine tomorrow. | 1 |
| 4 | It's fine today. But it'll rain tomorrow. | 1 |
+----+--------------------------------------------------+---------------------------------------------------+
3 rows in set (0.00 sec)
The result having the search word fine more, i.e. id = 3 message having the higher search score, is displayed first. And you also get search score by using MATCH AGAINST in SELECT phrase.
You can use AS to change the attribute name.
mysql> SELECT *, MATCH (content) AGAINST ("+fine" IN BOOLEAN MODE) AS score FROM diaries WHERE MATCH (content) AGAINST ("+fine" IN BOOLEAN MODE) ORDER BY MATCH (content) AGAINST ("+fine" IN BOOLEAN MODE) DESC;
+----+--------------------------------------------------+-------+
| id | content | score |
+----+--------------------------------------------------+-------+
| 3 | It's fine today. It'll be fine tomorrow as well. | 2 |
| 1 | It'll be fine tomorrow. | 1 |
| 4 | It's fine today. But it'll rain tomorrow. | 1 |
+----+--------------------------------------------------+-------+
3 rows in set (0.00 sec)
4.4.4. How to specify the parser for full text search#
MySQL has the following syntax to specify the parser [2] for full text search.
FULLTEXT INDEX (content) WITH PARSER parser_name
To use this syntax, you need to register all parsers in MySQL beforehand. On the other hand, Groonga can dynamically add a tokenizer, that is a parser in MySQL. So if use this syntax in Mroonga, tokenizers that are added in Groonga dynamically cannot be supported. We think that this limitation decreases the convenience, and we choose our own syntax using COMMENT like the following.
FULLTEXT INDEX (content) COMMENT 'tokenizer "TokenMecab"'
Note
COMMENT in FULLTEXT INDEX is only supported MySQL 5.5 or later. If you use MySQL 5.1, use mroonga_default_parser variable described below.
You can specify one of following values as the tokenizer.
Tokenizer |
Description |
|---|---|
|
( |
|
Added in version 8.07: It does not tokenize at all. Use |
|
It tokenises in bigram. But continuous alphabets, numbers or symbols are treated as a token. So there can exist tokes with 3 letters or more. It is to reduce noises. This is the default value. |
|
It tokenises using MeCab. Groonga should be built with MeCab support. |
|
It tokenises in bigram. Unlike When you use |
|
It tokenise in bigram. In addition to When you use |
|
It tokenise in bigram. In addition to
When you use |
|
It tokenise in bigram. Unlike When you use |
|
It tokenise in bigram. Unlike When you use |
|
It tokenise in bigram. Unlike When you use |
|
It tokenise in bigram. Unlike
When you use |
|
It tokenise by splitting with a white space.
|
|
It tokenise by splitting with a null character (
|
|
It tokenises in unigram. But continuous alphabets, numbers or symbols are treated as a token. So there can exist tokes with 2 letters or more. It is to reduce noises. |
|
It tokenises in trigram. But continuous alphabets, numbers or symbols are treated as a token. So there can exist tokes with 4 letters or more. It is to reduce noises. |
You can specify the default tokenizer by passing --with-default-tokenizer option in configure when you build Mroonga.
./configure --with-default-tokenizer TokenMecab ...
Or you can set mroonga_default_tokenizer variable in my.cnf or by SQL. If you specify it in my.cnf, the change will not be lost after restarting MySQL, but you need to restart MySQL to make it effective. On the other hand, if you set it in SQL, the change is effective immediately, but it will be lost when you restart MySQL.
my.cnf:
[mysqld]
mroonga_default_tokenizer=TokenMecab
SQL:
mysql> SET GLOBAL mroonga_default_tokenizer = TokenMecab;
Query OK, 0 rows affected (0.00 sec)
4.4.5. How to specify the normalizer#
Mroonga uses normalizer corresponding to the encoding of document. It is used when tokenizing text and storing table key.
It is used NormalizerMySQLGeneralCI normalizer when the encoding is
utf8_general_ci or utf8mb4_general_ci.
It is used NormalizerMySQLUnicodeCI normalizer when the encoding is
utf8_unicode_ci or utf8mb4_unicode_ci.
It isn’t used normalizer when the encoding is utf8_bin.
Here is an example that uses NormalizerMySQLUnicodeCI normalizer by specifying utf8_unicode_ci.:
mysql> SET NAMES utf8;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE diaries (
-> day DATE PRIMARY KEY,
-> content VARCHAR(64) NOT NULL,
-> FULLTEXT INDEX (content)
-> ) Engine=Mroonga DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
Query OK, 0 rows affected (0.18 sec)
mysql> INSERT INTO diaries VALUES ("2013-04-23", "ブラックコーヒーを飲んだ。");
Query OK, 1 row affected (0.00 sec)
mysql> SELECT * FROM diaries
-> WHERE MATCH (content) AGAINST ("+ふらつく" IN BOOLEAN MODE);
+------------+-----------------------------------------+
| day | content |
+------------+-----------------------------------------+
| 2013-04-23 | ブラックコーヒーを飲んだ。 |
+------------+-----------------------------------------+
1 row in set (0.00 sec)
mysql> SELECT * FROM diaries
-> WHERE MATCH (content) AGAINST ("+ﾌﾞﾗｯｸ" IN BOOLEAN MODE);
+------------+-----------------------------------------+
| day | content |
+------------+-----------------------------------------+
| 2013-04-23 | ブラックコーヒーを飲んだ。 |
+------------+-----------------------------------------+
1 row in set (0.00 sec)
Mroonga has the following syntax to specify Groonga’s normalizer:
FULLTEXT INDEX (content) COMMENT 'normalizer "NormalizerAuto"'
See Groonga’s documentation about normalizer for more details.
Here is an example that uses NormalizerAuto normalizer:
mysql> SET NAMES utf8;
Query OK, 0 rows affected (0.00 sec)
mysql> CREATE TABLE diaries (
-> day DATE PRIMARY KEY,
-> content VARCHAR(64) NOT NULL,
-> FULLTEXT INDEX (content) COMMENT 'normalizer "NormalizerAuto"'
-> ) Engine=Mroonga DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci;
Query OK, 0 rows affected (0.19 sec)
mysql> INSERT INTO diaries VALUES ("2013-04-23", "ブラックコーヒーを飲んだ。");
Query OK, 1 row affected (0.00 sec)
mysql> SELECT * FROM diaries
-> WHERE MATCH (content) AGAINST ("+ふらつく" IN BOOLEAN MODE);
Empty set (0.00 sec)
mysql> SELECT * FROM diaries
-> WHERE MATCH (content) AGAINST ("+ﾌﾞﾗｯｸ" IN BOOLEAN MODE);
+------------+-----------------------------------------+
| day | content |
+------------+-----------------------------------------+
| 2013-04-23 | ブラックコーヒーを飲んだ。 |
+------------+-----------------------------------------+
1 row in set (0.00 sec)
4.4.6. How to get snippet (Keyword in context)#
Mroonga provides functionality to get keyword in context. It is implemented as mroonga_snippet() UDF.
4.4.7. Logging#
Mroonga outputs the logs by default.
Log files are located in MySQL’s data directory with the filename groonga.log.
Here is the example of the log.
2010-10-07 17:32:39.209379|n|b1858f80|mroonga 1.10 started.
2010-10-07 17:32:44.934048|d|46953940|hash get not found (key=test)
2010-10-07 17:32:44.936113|d|46953940|hash put (key=test)
The default log level is NOTICE, i.e. we have important information only and we don’t have debug information etc.).
You can get the log level by mroonga_log_level system variable, that is a global variable. You can also modify it dynamically by using SET phrase.
mysql> SHOW VARIABLES LIKE 'mroonga_log_level';
+-------------------+--------+
| Variable_name | Value |
+-------------------+--------+
| mroonga_log_level | NOTICE |
+-------------------+--------+
1 row in set (0.00 sec)
mysql> SET GLOBAL mroonga_log_level=DUMP;
Query OK, 0 rows affected (0.00 sec)
mysql> SHOW VARIABLES LIKE 'mroonga_log_level';
+-------------------+-------+
| Variable_name | Value |
+-------------------+-------+
| mroonga_log_level | DUMP |
+-------------------+-------+
1 row in set (0.00 sec)
Available log levels are the followings.
NONE
EMERG
ALERT
CRIT
ERROR
WARNING
NOTICE
INFO
DEBUG
DUMP
See mroonga_log_level about details.
You can reopen the log file by FLUSH LOGS. If you want to rotate the log file without stopping MySQL server, you can do in the following procedure.
change the file name of
groonga.log(by using OS’s mv command etc.).invoke “FLUSH LOGS” in MySQL server (by mysql command or mysqladmin command).
4.4.8. Next step#
Now, you can use Mroonga as wrapper mode! If you want Mroonga to be faster, see also Optimizations.
Footnotes