5.5.5. mroonga_snippet()

5.5.5.1. Summary

mroonga_snippet() UDF provides functionality to get keyword in context.

Note

This feature is in experimental stage. So, the required arguments or value is changed without notice in the future.

5.5.5.2. Syntax

mroonga_snippet() has required parameter and optional parameter:

mroonga_snippet(document,
                max_length,
                max_count,
                encoding,
                skip_leading_spaces,
                html_escape,
                snippet_prefix,
                snippet_suffix,
                word1, word1_prefix, word1_suffix,
                ...,
                [wordN, wordN_prefix, wordN_suffix])

5.5.5.3. Usage

There is a case that you want to extract keyword and surrounding text as a search results.

Snippet means 'keyword and surrounding text'. It is called 'Keyword in context'.

mroonga_snippet() function provides the way to get snippet from search results.

You can use mroonga_snippet() UDF in storage mode and wrapper mode.

mroonga_snippet() function is included in Mroonga as a User-Defined Function (UDF), but if you have not yet register it in MySQL by CREATE FUNCTION, you need to invoke the following SQL for defining a function.

mysql> CREATE FUNCTION mroonga_snippet RETURNS STRING SONAME 'ha_mroonga.so';

mroonga_snippet() function is useful for searching the text which contains keyword and associated one by using MATCH .. AGAINST syntax.

Imagine searching the document which contains 'fulltext' as a keyword. Assume that some keyword such as 'MySQL' and 'search' are associated with 'fulltext'.

mroonga_snippet() function meets above.

Here is the schema definition for execution examples(storage mode):

CREATE TABLE `snippet_test` (
  `id` int(11) NOT NULL,
  `text` text,
  PRIMARY KEY (`id`),
  FULLTEXT KEY `text` (`text`)
) ENGINE=mroonga DEFAULT CHARSET=utf8

Here is the schema definition for execution examples(wrapper mode):

CREATE TABLE `snippet_test` (
  `id` int(11) NOT NULL,
  `text` text,
  PRIMARY KEY (`id`),
  FULLTEXT KEY `text` (`text`)
) ENGINE=mroonga COMMENT 'engine = "innodb"' DEFAULT CHARSET=utf8

Here is the sample data for execution examples:

INSERt INTO snippet_test (id, text) VALUES (1, 'An open-source fulltext search engine and column store.');
INSERT INTO snippet_test (id, text) VALUES (2, 'An open-source storage engine for fast fulltext search with MySQL.');
INSERT INTO snippet_test (id, text) VALUES (3, 'Tritonn is a patched version of MySQL that supports better fulltext search function with Senna.');

Here is the results of execution examples:

mysql> SELECT * FROM snippet_test;
+----+-------------------------------------------------------------------------------------------------+
| id | text                                                                                            |
+----+-------------------------------------------------------------------------------------------------+
|  1 | An open-source fulltext search engine and column store.                                         |
|  2 | An open-source storage engine for fast fulltext search with MySQL.                              |
|  3 | Tritonn is a patched version of MySQL that supports better fulltext search function with Senna. |
+----+-------------------------------------------------------------------------------------------------+
3 rows in set (0.00 sec)

mysql> SELECT id, text, mroonga_snippet(text, 8, 2, 'ascii_general_ci', 1, 1, '...', '...<br>', 'fulltext', '<span class="w1">', '</span>', 'MySQL', '<span class="w2">', '</span>', 'search', '<span calss="w3">', '</span>') FROM snippet_test WHERE MATCH(text) AGAINST ('fulltext');
+----+-------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| id | text                                                                                            | mroonga_snippet(text, 8, 2, 'ascii_general_ci', 1, 1, '...', '...<br>', 'fulltext', '<span class="w1">', '</span>', 'MySQL', '<span class="w2">', '</span>', 'search', '<span calss="w3">', '</span>') |
+----+-------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
|  1 | An open-source fulltext search engine and column store.                                         | ...<span class="w1">fulltext</span>...<br>... <span calss="w3">search</span> ...<br>                                                                                                                   |
|  2 | An open-source storage engine for fast fulltext search with MySQL.                              | ...<span class="w1">fulltext</span>...<br>... <span calss="w3">search</span> ...<br>                                                                                                                   |
|  3 | Tritonn is a patched version of MySQL that supports better fulltext search function with Senna. | ...f <span class="w2">MySQL</span> ...<br>...<span class="w1">fulltext</span>...<br>                                                                                                                   |
+----+-------------------------------------------------------------------------------------------------+--------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
3 rows in set (0.00 sec)

The keyword 'fulltext' and associated keyword 'MySQL' and 'search' has been extracted.

5.5.5.4. Parameters

5.5.5.4.1. Required parameters

There are many required parameters.

5.5.5.4.1.1. document

The column name or string value is required.

5.5.5.4.1.2. max_length

The max length of snippet (bytes) is required.

5.5.5.4.1.3. max_count

The max elements of snippets (N word) is required.

5.5.5.4.1.4. encoding

The encoding of document is required. You can specify the value of encoding such as 'ascii_general_ci', 'cp932_japanese_ci', 'eucjpms_japanese_ci' and so on.

5.5.5.4.1.5. skip_leading_spaces

Specify whether skip leading spaces or not. Specify the value 1 for skipping leading spaces, 0 for not.

5.5.5.4.1.6. html_escape

HTML escape is enabled or not. Specify the value 1 for enabling HTML escape, 0 for not.

5.5.5.4.1.7. prefix

The start text of snippet.

5.5.5.4.1.8. suffix

The end text of snippet.

5.5.5.4.2. Optional parameters

There is one optional group parameter, wordN related prefix and suffix.

5.5.5.4.2.1. wordN

Specify any word.

5.5.5.4.2.2. wordN_prefix

It is the start text of wordN.

5.5.5.4.2.3. wordN_suffix

It is the end text of wordN.

5.5.5.5. Return value

It returns snippet string.