Plucene::Search::Query - base class for queries

Plucene documentation Contained in the Plucene distribution.

Index

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NAME

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Plucene::Search::Query - base class for queries

SYNOPSIS

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	my $s_query = Plucene::Search::Query::Subclass->new({
		boost => $boost_factor});

	my $scorer = $s_query->scorer($query, $searcher, $reader);

DESCRIPTION

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This is an abstract base class for queries.

A query is a specification of the content an properties of the desired documents. Every search is done by matching a query against the document index and locating the ones that match the query.

The simplest query specifies a single term (or word) that is to be matched against a single field (e.g. 'author') of each of the documents in the index. This kind of query matches any document that contains the term in the specified field.

A more complex queries may contain nested queries with 'and', 'or', 'not' or 'phrase' relations. Queries may also contains specification of which document fields to match against the various parts of the query (.e.g. 'authors' and 'title') and hints that may effects the ranking of the matched documents ('boost' factor).

METHODS

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new

	my $s_query = Plucene::Search::Query::Subclass->new({
		boost => $boost_factor});

boost

Get / set this attribute

scorer

	my $scorer = $s_query->scorer
		(Plucene::Search::Query $query, $searcher, $reader);

prepare

Does nothing

sum_squared_weights / normalize / _scorer

These must be defined in a subclass

Plucene documentation Contained in the Plucene distribution. 
package Plucene::Search::Query;


use strict;
use warnings;

use base qw/Class::Accessor::Fast/;
__PACKAGE__->mk_accessors(qw/boost/);


sub new {
	my ($self, $opts) = @_;
	$opts->{boost} = 1 unless exists $opts->{boost};
	$self->SUPER::new($opts);
}


sub scorer {
	my ($class, $query, $searcher, $reader) = @_;

	$query->prepare($reader);
	my $sum = $query->sum_squared_weights($searcher) || 1;
	my $norm = 1 / sqrt($sum);
	$query->normalize($norm);
	return $query->_scorer($reader);
}


sub prepare { }

sub sum_squared_weights {
	die "sum_squared_weights must be defined in a subclass";
}
sub normalize { die "normalize must be defined in a subclass" }
sub _scorer   { die "_scorer must be defined in a subclass" }

1;