Full-Text Module

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This XQuery Module extends the W3C Full Text Recommendation with some useful 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.

Conventions

All functions in this module are assigned to the http://basex.org/modules/ft namespace, which is statically bound to the ft prefix.
All errors are assigned to the http://basex.org/errors namespace, which is statically bound to the bxerr prefix.

Functions

ft:search

Updated with Version 7.3: second argument generalized, third parameter added.

Signatures ft:search($db as item(), $terms as item()*) as text()*
ft:search($db as item(), $terms as item()*, $options as item()) as text()*
Summary Returns all text nodes from the full-text index of the database node $db that contain the specified $terms.
The options used for building the full-text will also be applied to the search terms. As an example, if the index terms have been stemmed, the search string will be stemmed as well.

The $options argument can be used to overwrite the default full-text options, which can be either specified

  • as children of an <options/> element, e.g.:
<options>
  <key1 value='value1'/>
  ...
</options>
  • as map, which contains all key/value pairs:
map { "key1" := "value1", ... }

The following keys are supported:

  • mode: determines the search mode (also called AnyAllOption). Allowed values are any, any word, all, all words, and phrase. any is the default search mode.
  • fuzzy: turns fuzzy querying on or off. Allowed values are an empty string or true, or false. By default, fuzzy querying is turned off.
  • wildcards: turns wildcard querying on or off. Allowed values are an empty string or true, or false. By default, wildcard querying is turned off.
Errors BXDB0004: the full-text index is not available.
BXFT0001: both fuzzy and wildcard querying was selected.
Examples
  • ft:search("DB", "QUERY") returns all text nodes of the database DB that contain the term QUERY.
  • ft:search("DB", (2010,2011), map { 'mode':='all' })
    returns all text nodes of the database DB that contain the numbers 2010 and 2011.
  • The last example iterates over five databases and returns all elements containing terms similar to Hello World in the text nodes:
let $terms := "Hello Worlds"
let $fuzzy := true()
let $options :=
  <options>
    <fuzzy>{ $fuzzy }</fuzzy>
  </options>
for $db in 1 to 3
let $dbname := 'DB' || $db
return ft:search($dbname, $terms, $options)/..

ft:mark

Signatures ft:mark($nodes as node()*) as node()*
ft:mark($nodes as node()*, $tag as xs:string) as node()*
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).
Examples
  • The following query returns <XML><mark>hello</mark> world</XML>, if one text node of the database DB has the value "hello world":
ft:mark(db:open('DB')//*[text() contains text 'hello'])
  • The following expression returns <p><b>word</b></p>:
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()*
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.
Examples
  • The following query may return <XML>...<b>hello</b>...<XML> if a text node of the database DB contains the string "hello world":
ft:extract(db:open('DB')//*[text() contains text 'hello'], 'b', 1)

ft:count

Signatures ft:count($nodes as node()*) as xs:integer
Summary Returns the number of occurrences of the search terms specified in a full-text expression.
Examples
  • ft:count(//*[text() contains text 'QUERY']) returns the xs:integer value 2 if a document contains two occurrences of the string "QUERY".

ft:score

Signatures ft:score($item as item()*) as xs:double*
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.
Examples
  • ft:score('a' contains text 'a') returns the xs:double value 1.

ft:tokens

Signatures ft:tokens($db as item()) as element(value)*
ft:tokens($db as item(), $prefix as xs:string) as element(value)*
Summary Returns all full-text tokens stored in the index of the database node $db, along with their numbers of occurrences.
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.
Errors BXDB0004: the full-text index is not available.

ft:tokenize

Signatures ft:tokenize($input as xs:string) as xs:string*
Summary Tokenizes the given $input string, using the current default full-text options.
Examples
  • ft:tokenize("No Doubt") returns the two strings no and doubt.
  • declare ft-option using stemming; ft:tokenize("GIFTS") returns a single string gift.

Errors

Code Description
BXFT0001 Both wildcards and fuzzy search have been specified as search options.

Changelog

Version 7.2
  • Updated: ft:search (second argument generalized, third parameter added)
Version 7.1