Marvin Humphrey
and 1 contributors

NAME

KinoSearch::Docs::Tutorial::Simple - Bare-bones search app.

Setup

Copy the html presentation of the US Constitution from the sample directory of the KinoSearch distribution to the base level of your web server's htdocs directory.

    $ cp -R sample/us_constitution /usr/local/apache2/htdocs/

Indexing: indexer.pl

Our first task will be to create an application called indexer.pl which builds a searchable "inverted index" from a collection of documents.

After we specify some configuration variables and load all necessary modules...

    #!/usr/local/bin/perl
    use strict;
    use warnings;
    
    # (Change configuration variables as needed.)
    my $path_to_index = '/path/to/index';
    my $uscon_source  = '/usr/local/apache2/htdocs/us_constitution';

    use KSx::Simple;
    use File::Spec::Functions qw( catfile );
    use HTML::TreeBuilder;

... we'll start by creating a KSx::Simple object, telling it where we'd like the index to be located and the language of the source material.

    my $simple = KSx::Simple->new(
        path     => $path_to_index,
        language => 'en',
    );

Next, we'll add a subroutine which extracts plain text from an HTML source file.

KSx::Simple won't be of any help with the task of text extraction, because it's not equipped to deal with source files directly. As a matter of principle, KinoSearch remains deliberately ignorant on the vast subject of file formats, preferring to focus instead on its core competencies of indexing and search. There are many excellent dedicated parsing modules available on CPAN; we'll use HTML::TreeBuilder.

    # Parse an HTML file from our US Constitution collection and return a
    # hashref with three keys: title, body, and url.
    sub parse_file {
        my $filename = shift;
        my $filepath = catfile( $uscon_source, $filename );
        my $tree     = HTML::TreeBuilder->new;
        $tree->parse_file($filepath);
        my $title_node = $tree->look_down( _tag => 'title' )
            or die "No title element in $filepath";
        my $bodytext_node = $tree->look_down( id => 'bodytext' )
            or die "No div with id 'bodytext' in $filepath";
        return {
            title   => $title_node->as_trimmed_text,
            content => $bodytext_node->as_trimmed_text,
            url     => "/us_constitution/$filename"
        };
    }

Add some elementary directory reading code...

    # Collect names of source html files.
    opendir( my $dh, $uscon_source )
        or die "Couldn't opendir '$uscon_source': $!";
    my @filenames = grep { $_ =~ /\.html/ && $_ ne 'index.html' } readdir $dh;

... and now we're ready for the meat of indexer.pl -- which occupies exactly one line of code.

    foreach my $filename (@filenames) {
        my $doc = parse_file($filename);
        $simple->add_doc($doc);  # ta-da!
    }

Search: search.cgi

As with our indexing app, the bulk of the code in our search script won't be KinoSearch-specific.

The beginning is dedicated to CGI processing and configuration.

    #!/usr/local/bin/perl -T
    use strict;
    use warnings;
    
    # (Change configuration variables as needed.)
    my $path_to_index = '/path/to/index';

    use CGI;
    use Data::Pageset;
    use HTML::Entities qw( encode_entities );
    use KSx::Simple;
    
    my $cgi           = CGI->new;
    my $q             = $cgi->param('q') || '';
    my $offset        = $cgi->param('offset') || 0;
    my $hits_per_page = 10;

Once that's out of the way, we create our KSx::Simple object and feed it a query string.

    my $simple = KSx::Simple->new(
        path     => $path_to_index,
        language => 'en',
    );
    my $hit_count = $simple->search(
        query      => $q,
        offset     => $offset,
        num_wanted => $hits_per_page,
    );

The value returned by search() is the total number of documents in the collection which matched the query. We'll show this hit count to the user, and also use it in conjunction with the parameters offset and num_wanted to break up results into "pages" of manageable size.

Calling search() on our Simple object turns it into an iterator. Invoking next() now returns hits one at a time as KinoSearch::Doc::HitDoc objects, starting with the most relevant.

    # Create result list.
    my $report = '';
    while ( my $hit = $simple->next ) {
        my $score = sprintf( "%0.3f", $hit->get_score );
        my $title = encode_entities( $hit->{title} );
        $report .= qq|
            <p>
              <a href="$hit->{url}"><strong>$title</strong></a>
              <em>$score</em>
              <br>
              <span class="excerptURL">$hit->{url}</span>
            </p>
            |;
    }

The rest of the script is just text wrangling. Notable aspects include the use of Data::Pageset to create paging links, and the encode_entities function from HTML::Entities to guard against cross-site scripting attacks.

    #---------------------------------------------------------------#
    # No tutorial material below this point - just html generation. #
    #---------------------------------------------------------------#
    
    # Generate paging links and hit count, print and exit.
    my $paging_links = generate_paging_info( $q, $hit_count );
    blast_out_content( $q, $report, $paging_links );
    
    # Create html fragment with links for paging through results n-at-a-time.
    sub generate_paging_info {
        my ( $query_string, $total_hits ) = @_;
        $query_string = encode_entities($query_string);
        my $paging_info;
        if ( !length $query_string ) {
            # No query?  No display.
            $paging_info = '';
        }
        elsif ( $total_hits == 0 ) {
            # Alert the user that their search failed.
            $paging_info
                = qq|<p>No matches for <strong>$query_string</strong></p>|;
        }
        else {
            my $current_page = ( $offset / $hits_per_page ) + 1;
            my $pager        = Data::Pageset->new(
                {   total_entries    => $total_hits,
                    entries_per_page => $hits_per_page,
                    current_page     => $current_page,
                    pages_per_set    => 10,
                    mode             => 'slide',
                }
            );
            my $last_result  = $pager->last;
            my $first_result = $pager->first;
    
            # Display the result nums, start paging info.
            $paging_info = qq|
                <p>
                    Results <strong>$first_result-$last_result</strong> 
                    of <strong>$total_hits</strong> 
                    for <strong>$query_string</strong>.
                </p>
                <p>
                    Results Page:
                |;
    
            # Create a url for use in paging links.
            my $href = $cgi->url( -relative => 1 ) . "?" . $cgi->query_string;
            $href .= ";offset=0" unless $href =~ /offset=/;
    
            # Generate the "Prev" link.
            if ( $current_page > 1 ) {
                my $new_offset = ( $current_page - 2 ) * $hits_per_page;
                $href =~ s/(?<=offset=)\d+/$new_offset/;
                $paging_info .= qq|<a href="$href">&lt;= Prev</a>\n|;
            }
    
            # Generate paging links.
            for my $page_num ( @{ $pager->pages_in_set } ) {
                if ( $page_num == $current_page ) {
                    $paging_info .= qq|$page_num \n|;
                }
                else {
                    my $new_offset = ( $page_num - 1 ) * $hits_per_page;
                    $href =~ s/(?<=offset=)\d+/$new_offset/;
                    $paging_info .= qq|<a href="$href">$page_num</a>\n|;
                }
            }
    
            # Generate the "Next" link.
            if ( $current_page != $pager->last_page ) {
                my $new_offset = $current_page * $hits_per_page;
                $href =~ s/(?<=offset=)\d+/$new_offset/;
                $paging_info .= qq|<a href="$href">Next =&gt;</a>\n|;
            }
    
            # Close tag.
            $paging_info .= "</p>\n";
        }
    
        return $paging_info;
    }
    
    # Print content to output.
    sub blast_out_content {
        my ( $query_string, $hit_list, $paging_info ) = @_;
        $query_string = encode_entities($query_string);
        print "Content-type: text/html\n\n";
        print qq|
    <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
        "http://www.w3.org/TR/html4/loose.dtd">
    <html>
    <head>
      <meta http-equiv="Content-type" 
        content="text/html;charset=ISO-8859-1">
      <link rel="stylesheet" type="text/css" 
        href="/us_constitution/uscon.css">
      <title>KinoSearch: $query_string</title>
    </head>
    
    <body>
    
      <div id="navigation">
        <form id="usconSearch" action="">
          <strong>
            Search the 
            <a href="/us_constitution/index.html">US Constitution</a>:
          </strong>
          <input type="text" name="q" id="q" value="$query_string">
          <input type="submit" value="=&gt;">
        </form>
      </div><!--navigation-->
    
      <div id="bodytext">
    
      $hit_list
    
      $paging_info
    
        <p style="font-size: smaller; color: #666">
          <em>
            Powered by 
            <a href="http://www.rectangular.com/kinosearch/">KinoSearch</a>
          </em>
        </p>
      </div><!--bodytext-->
    
    </body>
    
    </html>
    |;
    }

OK... now what?

KSx::Simple is perfectly adequate for some tasks, but it's not very flexible. Many people find that it doesn't do at least one or two things they can't live without.

In our next tutorial chapter, BeyondSimple, we'll rewrite our indexing and search scripts using the classes that KSx::Simple hides from view, opening up the possibilities for expansion; then, we'll spend the rest of the tutorial chapters exploring these possibilities.

COPYRIGHT

Copyright 2005-2010 Marvin Humphrey

LICENSE, DISCLAIMER, BUGS, etc.

See KinoSearch version 0.30.