Editing API:EPrints/Search

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==NAME==
EPrints::Search - retrieve objects based on search criteria

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==DESCRIPTION==
The Search object represents the conditions of a single search.

Executing a search returns an [[API:EPrints/List|EPrints::List]] object.

A search expression can also render itself as a web-form, populate itself with values from that web-form and render the results as a web page.

[[API:EPrints/Plugin/Search|EPrints::Plugin::Search]] provides a pluggable architecture for searching EPrints.

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==SYNOPSIS==
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===Searching for Eprints===
<pre>  $ds = $repo-&gt;dataset( "archive" );
  
  # NB 'archive' is an implicit filter on eprint.status
  $list = $ds->search(filters => [{
    meta_fields => [qw( eprintid )], value => 23,
  }]);
  
  $list = $ds->search(search_fields => [{
    meta_fields => [qw( creators_name )], value => "John Smith",
  }]);
  
  $searchexp = $ds->prepare_search();
  $searchexp->add_field(
    fields => [
      $ds->field('creators_name')
    ],
    value => "John Smith",
    match => "EQ", # EQuals
  );
  $searchexp->add_field(
    fields => [
      $ds->field('title')
    ],
    value => "eagle buzzard",
    match => "IN", # INdex
  );</pre>

See [[API:EPrints/DataSet|EPrints::DataSet]] for more API methods for constructing search objects.

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===Getting Results===
<pre>  $list = $searchexp-&gt;perform_search;
  
  my $count = $list->count;
  
  my $ids = $results->ids( 0, 10 );
  my $ids = $results->ids; # Get all matching ids
  
  my $info = { matches => 0 };
  sub fn {
    my( $session, $dataset, $eprint, $info ) = @_;
    $info->{matches}++;
  };
  $list->map( \&fn, $info );</pre>

See [[API:EPrints/List|EPrints::List]] for more.

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==METHODS==
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===new===

<source lang="perl">$searchexp = EPrints::Search->new( %params )

</source>
Create a new search expression.

The parameters are split into two parts. The general parameters and those which influence how the HTML form is rendered, and the results displayed.

GENERAL PARAMETERS

* session (required)
: The current [[API:EPrints/Session|EPrints::Session]]

* dataset OR dataset_id (required)
: Either the [[API:EPrints/DataSet|EPrints::DataSet]] to search, or the ID of it.

* allow_blank (default 0)
: Unless this is set, a search with no conditions will return zero records  rather than all records.

* satisfy_all (default 1)
: If this is true than all search-fields much be satisfied, if false then  results matching any search-field will be returned.

* search_fields
: A reference to an array of search field configuration structures. Each  takes the form { id=&gt;"...", default=&gt;"..", meta_fields=&gt;"..." } where the meaning is the same as for search configuration in ArchiveConfig.

: Search fields can also be added to the search expression after it has been constructed.

* order
: The order the results should be returned. This is a key to the list of orders available to this dataset, defined in ArchiveConfig.pm

* custom_order
: "order" limits you to the orders specified in ArchiveConfig, and is usually used by the web page based searching. custom_order allows you to specify any order you like. The format is  foo/-bar. This means that the results will be sorted by foo and then any with equal foo values will be reverse sorted by bar. More than 2 fields can be specified.

* keep_cache
: If true then the search results produced will be stored in the database even after the current script ends. This is useful for speeding up  page 2 onwards of a search.

: keep_cache may get set to true anyway for various reasons, but setting the parameter makes certain of it.

* cache_id
: The ID of a cached search. The cache contains both the results of the search, and the parameters used for the search.

: If the cache still exists, it will set the default values of the  search fields, and when the search is performed it will skip the  search and build a search results object directly from the cache.

* limit
: Limit the number of matching records to limit.

WEB PAGE RELATED PARAMETERS

* prefix (default "")
: When generating the web form and reading back from the web form, the prefix is inserted before the form names of all fields. This is useful if you need to put two search expressions in a single form for some reason.

* staff (default 0)
: If true then this is a "staff" search, which prevents searching unless the user is staff, and the results link to the staff URL of an item rather than the public URL.

* filters
: A reference to an array of filter definitions.

: Filter definitions take the form of: { value=&gt;"..", match=&gt;"..", merge=&gt;"..", id=&gt;".." } and work much like normal search fields except that they do not appear in the web form so force certain search parameters on the user.

: An optional parameter of describe=&gt;0 can be set to supress the filter being mentioned in the description of the search.

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===from_cache===

<source lang="perl">$ok = $thing->from_cache( $id )

</source>
Populate this search expression with values from the given cache.

Return false if the cache does not exist.

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===add_field===

<source lang="perl">$searchfield = $searchexp->add_field( %opts )

</source>
<pre>  fields - one or more fields to search over
  match - match type
  merge - merge type
  value - value to match against (for EX matches, NULL = is_null!)
  id - search field id, if not the name of the first field
  filter - is filter-type
  show_help - show help in search input</pre>

Adds a new search in $fields which is either a single [[API:EPrints/MetaField|EPrints::MetaField]] or a list of fields in an array ref with default $value. If a search field already exists, the value of that field is replaced with $value.

See [[API:EPrints/Search/Field|EPrints::Search::Field]] for details on match/merge etc.

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Note relating to the <code>for EX matches, NULL = is_null</code> documentation above.

To search for items with no value, use something similar to this - explicitly setting the value to undef.:
<source lang="perl">
### Example: search for items in the review area with no date set.
my $ds = $session->dataset( "buffer" );
my $searchexp = $ds->prepare_search();
$searchexp->add_field(
    fields => [
      $ds->field( 'date' ),
    ],
    value => undef,
    match => "EX",
);
</source>


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===clear===

<source lang="perl">$searchexp->clear

</source>
Clear the search values of all search fields in the expression.

Resets satisfy_all to true.

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===get_satisfy_all===

<source lang="perl">$bool = $searchexp->get_satisfy_all

</source>
Return true if this search requires that all the search fields with values are satisfied. 

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===is_blank===

<source lang="perl">$boolean = $searchexp->is_blank

</source>
Return true is this searchexpression has no conditions set, otherwise true.

If any field is set to "exact" then it can never count as unset.

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===serialise===

<source lang="perl">$string = $searchexp->serialise

</source>
Return a text representation of the search expression, for persistent storage. Doesn't store table or the order by fields, just the field names, values, default order and satisfy_all.

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===from_string===

<source lang="perl">$searchexp->from_string( $string )

</source>
Unserialises the contents of $string but only into the fields alrdeady existing in $searchexp. Set the order and satisfy_all mode but do not  affect the dataset or allow blank.

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===clone===

<source lang="perl">$newsearchexp = $searchexp->clone

</source>
Return a new search expression which is a duplicate of this one.

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===get_conditons===

<source lang="perl">$conditions = $searchexp->get_conditons

</source>
Return a tree of [[API:EPrints/Search/Condition|EPrints::Search::Condition]] objects describing the simple steps required to perform this search.

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===get_dataset===

<source lang="perl">$dataset = $searchexp->get_dataset

</source>
Return the [[API:EPrints/DataSet|EPrints::DataSet]] which this search relates to.

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===set_dataset===

<source lang="perl">$searchexp->set_dataset( $dataset )

</source>
Set the [[API:EPrints/DataSet|EPrints::DataSet]] which this search relates to.

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===render_description===

<source lang="perl">$xhtml = $searchexp->render_description

</source>
Return an XHTML DOM description of this search expressions current parameters.

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===render_conditions_description===

<source lang="perl">$xhtml = $searchexp->render_conditions_description

</source>
Return an XHTML DOM description of this search expressions conditions. ie title is "foo" 

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===render_order_description===

<source lang="perl">$xhtml = $searchexp->render_order_description

</source>
Return an XHTML DOM description of how this search is ordered.

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===set_property===

<source lang="perl">$searchexp->set_property( $property, $value );

</source>
Set any single property of this search, such as the order.

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===get_searchfields===

<source lang="perl">@search_fields = $searchexp->get_searchfields()

</source>
Return the [[API:EPrints/Search/Field|EPrints::Search::Field]] objects relating to this search.

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===get_non_filter_searchfields===

<source lang="perl">@search_fields = $searchexp->get_non_filter_searchfields();

</source>
Return the [[API:EPrints/Search/Field|EPrints::Search::Field]] objects relating to this search, which are normal search fields, and not "filters".

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===get_set_searchfields===

<source lang="perl">@search_fields = $searchexp->get_set_searchfields

</source>
Return the searchfields belonging to this search expression which have a value set. 

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===get_cache_id===

<source lang="perl">$cache_id = $searchexp->get_cache_id

</source>
Return the ID of the cache containing the results of this search, if known.

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===perform_search===

<source lang="perl">$results = $searchexp->perform_search

</source>
Execute this search and return a [[API:EPrints/List|EPrints::List]] object representing the results.

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===perform_distinctby===

<source lang="perl">$ids_map = $searchexp->perform_distinctby( $fields )

</source>
Perform a DISTINCT on $fields to find all unique ids by value.

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===perform_groupby===

<source lang="perl">($values, $counts) = $searchexp->perform_groupby( $field )

</source>
Perform a SQL GROUP BY on $field based on the current search parameters.

Returns two array references, one containing a list of unique values and one a list of counts for each value.

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===get_ids_by_field_values===

<source lang="perl">$hash = $searchexp->get_ids_by_field_values( $field )

</source>
Find the ids for each unique value in $field.

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==COPYRIGHT==
Copyright 2000-2011 University of Southampton.

This file is part of EPrints http://www.eprints.org/.

EPrints is free software: you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later version.

EPrints is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License along with EPrints.  If not, see http://www.gnu.org/licenses/.

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