KinoSearch::Docs::TutoUser:ContribuKinoSearch::Docs::Tutorial::QueryObjects(3)NAMEKinoSearch::Docs::Tutorial::QueryObjects - Use Query objects instead of
query strings.
DESCRIPTION
Until now, our search app has had only a single search box. In this
tutorial chapter, we'll move towards an "advanced search" interface, by
adding a "category" drop-down menu. Three new classes will be
required:
· QueryParser - Turn a query string into a Query object.
· TermQuery - Query for a specific term within a specific field.
· ANDQuery - "AND" together multiple Query objects to produce an
intersected result set.
Adaptations to indexer.pl
Our new "category" field will be a StringType field rather than a
FullTextType field, because we will only be looking for exact matches.
It needs to be indexed, but since we won't display its value, it
doesn't need to be stored.
my $cat_type = KinoSearch::Plan::StringType->new( stored => 0 );
$schema->spec_field( name => 'category', type => $cat_type );
There will be three possible values: "article", "amendment", and
"preamble", which we'll hack out of the HTML source file's name during
our "parse_file" subroutine:
my $category
= $filename =~ /art/ ? 'article'
: $filename =~ /amend/ ? 'amendment'
: $filename =~ /preamble/ ? 'preamble'
: die "Can't derive category for $filename";
return {
title => $title_node->as_trimmed_text,
content => $bodytext_node->as_trimmed_text,
url => "/us_constitution/$filename",
category => $category,
};
Adaptations to search.cgi
The "category" constraint will be added to our search interface using
an HTML "select" element:
# Build up the HTML "select" object for the "category" field.
sub generate_category_select {
my $cat = shift;
my $select = qq|
<select name="category">
<option value="">All Sections</option>
<option value="article">Articles</option>
<option value="amendment">Amendments</option>
</select>|;
if ($cat) {
$select =~ s/"$cat"/"$cat" selected/;
}
return $select;
}
We'll start off by loading our new modules and extracting our new CGI
parameter.
use KinoSearch::Search::QueryParser;
use KinoSearch::Search::TermQuery;
use KinoSearch::Search::ANDQuery;
...
my $category = $cgi->param('category') || '';
QueryParser's constructor requires a "schema" argument. We can get
that from our IndexSearcher:
# Create an IndexSearcher and a QueryParser.
my $searcher = KinoSearch::Search::IndexSearcher->new(
index => $path_to_index,
);
my $qparser = KinoSearch::Search::QueryParser->new(
schema => $searcher->get_schema,
);
Previously, we have been handing raw query strings to IndexSearcher.
Behind the scenes, IndexSearcher has been using a QueryParser to turn
those query strings into Query objects. Now, we will bring QueryParser
into the foreground and parse the strings explicitly.
my $query = $qparser->parse($q);
If the user has specified a category, we'll use an ANDQuery to join our
parsed query together with a TermQuery representing the category.
if ($category) {
my $category_query = KinoSearch::Search::TermQuery->new(
field => 'category',
term => $category,
);
$query = KinoSearch::Search::ANDQuery->new(
children => [ $query, $category_query ]
);
}
Now when we execute the query...
# Execute the Query and get a Hits object.
my $hits = $searcher->hits(
query => $query,
offset => $offset,
num_wanted => $hits_per_page,
);
... we'll get a result set which is the intersection of the parsed
query and the category query.
Congratulations!
You've made it to the end of the tutorial.
SEE ALSO
For additional thematic documentation, see the KinoSearch Cookbook.
ANDQuery has a companion class, ORQuery, and a close relative,
RequiredOptionalQuery.
COPYRIGHT AND LICENSE
Copyright 2008-2010 Marvin Humphrey
This program is free software; you can redistribute it and/or modify it
under the same terms as Perl itself.
perl v5.14.12KinoSearch::Docs::Tutorial::QueryObjects(3)
