Editing API:EPrints/Plugin/Search/Xapian (section)

==DESCRIPTION==
<pre>  Xapian is a highly adaptable toolkit which allows developers to easily add
  advanced indexing and search facilities to their own applications. It supports
  the Probabilistic Information Retrieval model and also supports a rich set of
  boolean query operators.</pre>

Xapian currently only supports simple searches.

Xapian simple searches are parsed by the Xapian query parser which supports prefixes for search terms:

<pre>  title:(eagle buzzard) abstract:"london wetlands"</pre>

The field prefixes are taken from the search configuration and constrain the following term (or bracketed terms) to that field only. If no prefix is given the entire Xapian index will be used i.e. it will search any indexed term, not just those from the search configuration fields. For example, the following simple search configuration:

<pre>  search_fields =&gt; [
    {
      id =&gt; "q",
         meta_fields =&gt; [
           "documents",
           "title",
           "abstract",
           "creators_name",
           "date"
         ]
    },
  ],</pre>

Allows the user to specify "documents", "title", "abstract", "creators_name" or "date" as a prefix to a search term. Omitting a prefix will match any field e.g. "publisher".

Terms can be negated by prefixing the term with '-':

<pre>  eagle -buzzard</pre>

Phrases can be specified by using quotes, for example  "Southampton University" won't match <em>University of Southampton</em>.

Terms are stemmed by default ('bubbles' becomes 'bubble') except if you use the term in a phrase.

Partial matches are supported by using '*':

<pre>  ameri* - americans, americas, amerillo etc.</pre>

Xapian search results are returned in a sub-class of [[API:EPrints/List|EPrints::List]] (a wrapper around a Xapian enquire object). Calling [[API:EPrints/List#count|EPrints::List/count]] will return an '''estimate''' of the total matches.

As Xapian has a higher 'qs' score than Internal it will (once enabled) override the default EPrints simple search. You can override this behaviour in '''cfg.d/plugins.pl''':

<pre>  $c-&gt;{plugins}{'Search::Xapian'}{params}{qs} = -1;</pre>

Or disable completely (including disabling indexing):

<pre>  $c-&gt;{plugins}{'Search::Xapian'}{params}{disable} = 1;</pre>

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