5.4.2. mroonga_snippet¶
5.4.2.1. 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.
5.4.2.2. 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]
5.4.2.3. 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.
5.4.2.4. Parameters¶
5.4.2.4.1. Required parameters¶
There are many required parameters.
5.4.2.4.1.1. document
¶
The column name or string value is required.
5.4.2.4.1.2. max_length
¶
The max length of snippet (bytes) is required.
5.4.2.4.1.3. max_count
¶
The max elements of snippets (N word) is required.
5.4.2.4.1.4. 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.
5.4.2.4.1.5. skip_leading_spaces
¶
Specify whether skip leading spaces or not. Specify the value 1 for skipping leading spaces, 0 for not.
5.4.2.4.1.6. html_escape
¶
HTML escape is enabled or not. Specify the value 1 for enabling HTML escape, 0 for not.
5.4.2.4.1.7. prefix
¶
The start text of snippet.
5.4.2.4.1.8. suffix
¶
The end text of snippet.
5.4.2.5. Return value¶
It returns snippet string.