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.\" ========================================================================
.\"
.IX Title "LucyX::Search::Filter 3pm"
.TH LucyX::Search::Filter 3pm "2015-03-06" "perl v5.20.2" "User Contributed Perl Documentation"
.\" For nroff, turn off justification.  Always turn off hyphenation; it makes
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.SH "NAME"
LucyX::Search::Filter \- Build a caching filter based on results of a Query.
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 10
\&    my %category_filters;
\&    for my $category (qw( sweet sour salty bitter )) {
\&        my $cat_query = Lucy::Search::TermQuery\->new(
\&            field => \*(Aqcategory\*(Aq,
\&            term  => $category,
\&        );
\&        $category_filters{$category} = LucyX::Search::Filter\->new( 
\&            query => $cat_query, 
\&        );
\&    }
\&    
\&    while ( my $cgi = CGI::Fast\->new ) {
\&        my $user_query = $cgi\->param(\*(Aqq\*(Aq);
\&        my $filter     = $category_filters{ $cgi\->param(\*(Aqcategory\*(Aq) };
\&        my $and_query  = Lucy::Search::ANDQuery\->new;
\&        $and_query\->add_child($user_query);
\&        $and_query\->add_child($filter);
\&        my $hits = $searcher\->hits( query => $and_query );
\&        ...
.Ve
.SH "DESCRIPTION"
.IX Header "DESCRIPTION"
A Filter is a Lucy::Search::Query subclass that can be used to filter
the results of another Query.  The effect is very similar to simply using the
wrapped inner query, but there are two important differences:
.IP "\(bu" 4
A Filter does not contribute to the score of the documents it matches.
.IP "\(bu" 4
A Filter caches its results, so it is more efficient if you use it more than
once.
.PP
To obtain logically equivalent results to the Filter but avoid the caching,
substitute the wrapped query but use \fIset_boost()\fR to set its \f(CW\*(C`boost\*(C'\fR to 0.
.SH "METHODS"
.IX Header "METHODS"
.SS "new"
.IX Subsection "new"
.Vb 3
\&    my $filter = LucyX::Search::Filter\->new(
\&        query => $query;
\&    );
.Ve
.PP
Constructor.  Takes one hash-style parameter, \f(CW\*(C`query\*(C'\fR, which must be an
object belonging to a subclass of Lucy::Search::Query.
.SH "BUGS"
.IX Header "BUGS"
Filters do not cache when used in a search cluster with LucyX::Remote's
SearchServer and SearchClient.