NAME
    Freq - An inverted text index.

ABSTRACT
    THIS IS ALPHA SOFTWARE

    Freq is a text indexer and search utility written in Perl and C. It has
    several special features not to be found in most available similar
    programs, namely arbitrarily complex sequence and alternation queries,
    and proximity searches with both exact counts and limits. There is no
    result ranking (yet).

    The index format draws some ideas from the Lucene search engine, with
    some simplifications and enhancements. The index segments are stored in
    a CDB disk hash (from dj bernstein).

SYNOPSIS
    Index documents:

      # cat textcorpus.txt | tokenize | indexstream index_dir
      # cat textcorpus.txt | tokenize | stopstop | indexstream index_dir
      # optimize index_dir

    Search:

      # freqsearch index_dir
      # (type search terms)

PROGRAMMING API
      use Freq;

      # open for indexing
      $index = Freq->open_write( "indexname" );
      $index->index_document( "docname", $string );
      $index->close_index();

      # open for searching
      $index = Freq->open_read( "indexname" );

      # Find all docs containing a phrase
      $result = $index->search( "this phrase and no other phrase" );

      # result is hashref:
      # { doc1 => [ match1, match2 ... matchN ],
      #   doc2 => [ match1, ... ]
      # }
      # ... where 'match' is the token location of each match within that doc.

SEARCH SYNTAX
    Sequences of words are enclosed in angle brackets '<' and '>'.
    Alternations are enclosed in square brackets '[' and ']'. These may be
    nested within each other as long as it makes logical sense. "<the quick
    [brown grey] fox>" is a simple valid phrase. Nested square brackets
    don't make sense, logically, so they aren't allowed. Also not allowed
    are adjacent angle bracket sequences. However, alternations may be
    adjacent, as in "<I [go went] [to from] the store>". As long as these
    rules are followed, search terms may be arbitrarily complex. For
    example:

    "<At [a the] council [of for] the [gods <deities we [love <believe in>]
    with all our [hearts strength]>] on olympus [hercules apollo athena
    <some guys>] [was were] [praised <condemned to eternal suffering in the
    underworld>]>"

    Two operators are available to do proximity searches. '#wN' represents
    *at least* N intervening skips between words (the number of between
    words plus 1). Thus "<The #w8 dog>" would match the text "The quick
    brown fox jumped over the lazy dog". If #w7 or lesser had been used it
    would not match, but if #w9 or greater had been used it would still
    match. Also there is the '#tN' operator, which represents *exactly* N
    intervening skips. Thus for the above example "<The #t8 dog>", and no
    other value, would match. These operators can be used after words or
    alternations, but no other place.

AUTHOR
    Ira Joseph Woodhead, ira at sweetpota dot to

SEE ALSO
    "Lucene" "Plucene" "CDB_File" "Inline"