Difference between revisions of "Full-Text Module"
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===Version 7.1=== | ===Version 7.1=== |
Revision as of 14:05, 5 March 2012
This module extends the W3C Full Text Recommendation with some useful XQuery functions: The index can be directly accessed, full-text results can be marked with additional elements, or the relevant parts can be extracted. Moreover, the score value, which is generated by the contains text
expression, can be explicitly requested from items. All functions are introduced with the ft:
prefix, which is linked to the statically declared http://basex.org/modules/ft
namespace.
Contents
Functions
ft:search
Signatures | ft:search($node as node(), $text as xs:string) as text()
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Summary | Performs a full-text index request on the specified XML node and returns all text nodes that contain the string $text . The index full-text options are used for searching, i.e., if the index terms were stemmed, the search string will be stemmed as well.
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Errors | BASX0001 is raised if the full-text index is not available. BASX0002 is raised if a referenced node is not stored in a database (i.e., references a main-memory XML fragment). |
Examples |
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ft:mark
Signatures | ft:mark($nodes as node()*) as node()* ft:mark($nodes as node()*, $tag as xs:string) as node()*
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Summary | Puts a marker element around the resulting $nodes of a full-text index request.The default tag name of the marker element is mark . An alternative tag name can be chosen via the optional $tag argument.Note that the XML node to be transformed must be an internal "database" node. The transform expression can be used to apply the method to a main-memory fragment (see example).
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Errors | BASX0002 is raised if a referenced node is not stored in a database (i.e., references a main-memory XML fragment). FOCA0002 is raised if $name is no valid QName.
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Examples |
ft:mark(db:open('DB')//*[text() contains text 'hello'])
copy $p := <p>word</p> modify () return ft:mark($p[text() contains text 'word'], 'b') |
ft:extract
Signatures | ft:extract($nodes as node()*) as node()* ft:extract($nodes as node()*, $tag as xs:string) as node()* ft:extract($nodes as node()*, $tag as xs:string, $length as xs:integer) as node()*
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Summary | Extracts and returns relevant parts of full-text results. It puts a marker element around the resulting $nodes of a full-text index request and chops irrelevant sections of the result.The default tag name of the marker element is mark . An alternative tag name can be chosen via the optional $tag argument.The default length of the returned text is 150 characters. An alternative length can be specified via the optional $length argument. Note that the effective text length may differ from the specified text due to formatting and readibility issues.
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Errors | BASX0002 is raised if a referenced node is not stored in a database (i.e., references a main-memory XML fragment). FOCA0002 is raised if $name is no valid QName.
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Examples |
ft:extract(db:open('DB')//*[text() contains text 'hello'], 'b', 1) |
ft:count
Signatures | ft:count($nodes as node()*) as xs:integer
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Summary | Returns the number of occurrences of the search terms specified in a full-text expression. |
Errors | BASX0002 is raised if a referenced node is not stored in a database (i.e., references a main-memory XML fragment). |
Examples |
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ft:score
Signatures | ft:score($item as item()*) as xs:double*
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Summary | Returns the score values (0.0 - 1.0) that have been attached to the specified items. 0 is returned a value if no score was attached.
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Examples |
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ft:tokens
Signatures | ft:tokens($db as item()) as element(value)* ft:tokens($db as item(), $prefix as xs:string) as element(value)*
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Summary | Returns all full-text tokens stored in the index, along with their numbers of occurrences. $db may either be an xs:string , denoting the database name, or a node stored in the database. If $prefix is specified, the returned nodes will be refined to the strings starting with that prefix. The prefix will be tokenized according to the full-text used for creating the index.
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Errors | BASX0001 is raised if the full-text index is not available. BASX0002 is raised if $db references a node that is not stored in a database (i.e., references a main-memory XML fragment).BASX0003 is raised if the addressed database cannot be opened. |
ft:tokenize
Signatures | ft:tokenize($input as xs:string) as xs:string*
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Summary | Tokenizes the given $input string, using the current default full-text options.
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Examples |
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Changelog
Version 7.1
- Added:
ft:tokens()
,ft:tokenize()