Revision history for Perl extension DBIx::TextIndex.

=head1 CHANGES

0.15
    WARNING: indexes will have to be recreated after upgrading to this version

    Changed inverted list tables: renamed "docs" to "term_docs" and removed
    redundant column "docs_vector".  Bit vectors are now built from postings
    stored in term_docs column.  Total index size should be reduced
    significantly with removal of docs_vector column.

    Implemented DBIx::TextIndex::TermDocsCache to reduce database queries

    Fixed bug where single word queries for high doc frequency terms would
    return no results

0.14
    Fixed memory leak in integer decoding

0.13
    Changed format for inverted list postings to compressed binary
    format.  Index sizes should be 50% smaller than with previous versions.
    Implemented XS code for fast coding and decoding.

    Renamed 'freq_d' to 'docfreq_t'.

    Bug fix: add_doc will only set bits in all_docs_vector if document
    was actually added

    UPGRADE warning, indexes will have to be rebuilt.

0.12
    Added _optimize_or_search(). If query contains just OR words,
    turn the rarest words into AND words to reduce result set size
    before scoring.  Practically, this makes queries behave more like
    "all of the words" instead of "any of the words," which seems to
    be what the average user expects.

    Changed all symbols 'occurence' to 'freq_d' (frequency of docs in
    entire collection that contain term)

    Multi-field queries will return the intersection of all fields
    instead of the union.

    Added method all_doc_ids().

    There is no longer any need to sort doc_ids before passing
    to add_doc().

    Added more tests. WARNING: MySQL database 'test' must be available
    on localhost for tests to succeed.

    UPGRADE WARNING: collection table format changed, new index table
    collection_all_docs_vector added, some field names have changed in
    inverted tables.  Any indexes created with 0.11 or earlier will have
    to be deleted and recreated.

    UPGRADE WARNING: all symbols with "document" have been renamed to
    "doc" for brevity.  Methods have also been renamed, e.g. add_document()
    is now add_doc().  The old method names will work, but are deprecated.

    Replaced option 'language' with 'charset'.  iso-8859-1 is the
    default charset.

    Added call to Text::Unaccent::unac_string (www.senga.org) to replace
    accented characters with plain ASCII equivalent.  Uses 'charset' option
    to determine mapping.
   
    UPGRADE WARNING: added structured exceptions using Exception::Class.
    Calls to search() now have to be wrapped with eval blocks to catch
    query exceptions.

0.11

    Bug fix: HTML tags are now changed to a single space, instead of
    empty string when indexing document. Prevents concatenation of words
    in some cases.

0.10

    Fixed collection table upgrade bug

0.09 

    Changed $MAX_WORD_LENGTH default to 20

    Allow numbers to be indexed as words

    Use HTML::Entities to decode entities in indexed documents, on by default. Set option decode_html_entities to 0 to disable.

    Use $dbh->tables to check for existence of tables (caution, may not
    work in DBI > 1.30).

0.08 

    Bug fix: add_mask() was not inserting masks

0.07

    UPGRADE WARNING: collection table format changed, use new method
    $index->upgrade_collection_table() to recreate collection table. 
    Calling initialize() method for a new collection will also upgrade
    collection table. Index backup recommended.

    Added error_ prefix to error message column names in collection table

    Added version column to collection table

    Added language column to collection table, removed czech_language column

    UPGRADE WARNING: instead of new({ czech_language => 1}), use
    new({ language => 'cz' })

    Bug fix: _store_collection_info() error if stop lists are not used

    unscored_search() will now return a scalar error message
    if an error occurs in search

    search() will croak if passed an invalid field name to search on

    Added documentation for mask operations

0.06 

    tripie's patch v2 updates:

    - a bug in document removing proccess related to incorrect
    'occurency' data updates when multi-field documents were removed,
    was fixed.  The methods remove_document() and _inverted_remove()
    were affected.

    - a bug related to wildcards in queries in form of "+word +next%"
    or "+word% +next%" was fixed

    - a bug related to "%" wildcards used while searching of
    multi-field documents was fixed

    - a bug related to stoplists and phrases that contain a
    non-stoplisted word together with a stoplisted word was fixed

    - a new full-featured solution of highligting of query words or
    patterns in content of resulting documents was added

    I've written a new module HTML::Highlight, that can be used
    either independently or together with DBIx::TextIndex. Its
    advantages include:

      - it makes highlighting very easy
      - takes phrases and wildcards into account
      - supports diacritics insensitive highlighting for iso-8859-2
        languages
      - takes HTML tags into account. That means when a user searches
        for for example 'font', than a FONT element in <FONT COLOR="red">
        does not get "highlighted".
		
    The module provides a very nice Google-like highlighting using
    different colors for different words or phrases.

    The module works together with DBIx::TextIndex using its new method
    html_highlight().

    The module can also be used to preview a context in which query
    words appear in resulting documents.
		
    - the old method highlight() was not changed nor removed for sake of
    compatibility with old code
	
    - I put a new 'html_search.cgi' script to examples/ to show how the new
    highligting and context previewing works.
	  
    - the HTML::Highlight module can be found on CPAN - 
    http://www.cpan.org/authors/id/T/TR/TRIPIE/

    - the new highlighting solution has been documented in a new section
    of the documentation
	  
  tripie v1 changes:

    added proximity indexing
      - based on positions of words in a document
      - by default it is disabled, activate it by new option "proximity_index"
      - very efficient for bigger documents, much worse for small ones
      - it's very big (approx. 20 bytes for each word)
      - allows fast proximity based searches in form of:
        ":2 some phrase" => matches "some nice phrase"
        ":1 some phrase" => matches only exact "some phrase"
        ":10 some phrase" => matches "some [1..9 words] phrase"
        defaults to ":1" when omitted
      - the proximity matches work only forwards, not backwards,
        that means:
        ":3 some phrase" does not match "phrase nice some" or "phrase some"

    rewrote the word splitter and query parser
      - added support for czech language diacritics insensitive indexing
        and searching (option "czech_language")
	(note: changed option to "charset", pass value "iso-8859-2"
	to enable -dkoch)
        that is implemented by converting both the indexed data and
	the query from iso-8859-2 to ASCII

      - this can also be used for other iso-8859-2 based Slavic languages

      - the above is performed by my module "CzFast" that can
        be found on CPAN (my CPAN id is "TRIPIE"), and is optional

    added partial pattern matching using wildcards "%" or "*"
      - these wildcards can be used at end of a word to match all words
        that begin with that word, ie.

        the "%" character means "match any characters"

        car%	==> matches "car", "cars", "careful", "cartel", ....

        the "*" character means "match also the plural form"

        car*	==> matches only "car" or "cars"

      - added option "min_wildcard_length" to specify minimal length of a
        word base appearing before the "%" wildcard character to avoid
        selection of excessive amount of results

    added a database abstraction layer - all SQL queries were moved to
    separate module (see lib/ and the docs for new "db" option) and
    polished a bit for better maintainability and possible support of
    other SQL dialects

    added stoplists
      - some words that are too common (are present in almost every document)
	are not indexed and are removed from the search query before processing
	to avoid expensive processing of excessively huge result sets
      - user is notified when a search does not produce any results because
	some words he used in his query were stoplisted (no_results_stop)
      - stoplists can be easily localized or modified 
      - default is not to use any stoplist, one or more stoplists 
	can be selected using the "stoplist" option
      - stoplist data files are in lib/
      - english (en) and czech (cz) stoplists are included
      - more than one stoplist can be used

    added a facility to remove documents from the index - 
      check the documentation for new method "remove_document" for more info.
	
      There is no way to recover all the space taken by the documents that are
      being removed. This method manages to recover approx. 80% of the space.
	
      It's recommended to rebuild the index when you remove a
      significant amount of documents.

    added a facility to obtain some statistical information about the index -
      check the documentation for new method "stat"

    max_word_length, phrase_threshold and result_threshold are now configurable
    options

    added configuration options to customize/localize the error messages
    (no_results etc.)

    all new configuration options are properly stored in collection's data

    max_word_length limit now works much better - all words are stripped
    down to the maximum size before they are stored to the index,
    and also all query words are stripped down to the maximum word
    size before they are proccessed. Now when the max word length
    is set to, say, six and a user searches for for example
    "consciousness", all documents containing any words beginning
    with "consci" are returned Therefore the new max_word_length
    option is not a limit of a word size, but rather a
    "resolution" preference.  added some comments and occasionally
    corrected indentation

    documented the enhancements

    bugfix: when RaiseError was set on a DBI connection, then one
    query which only switched off PrintError to avoid some problems, failed

    note: the interface was not changed - old code using this module should
    run without any changes

    Thanks for this excellent module and please excuse my inferior English !

    Tomas Styblo, tripie@cpan.org

0.05

    Added unscored_search() which returns a reference to an array of
doc_ids, without scores.  Should be much faster than scored search.

    Added error handling in case _occurence() doesn't return a number.

0.04

    Bug fix: add_document() will return if passed empty array ref instead
of producing error.

    Changed _boolean_compare() and _phrase_search() so and_words and
phrases behave better in multiple-field searches. Result set for each
field is calculated first, then union of all fields is taken for
final result set.

    Scores are scaled lower in _search().

0.03

    Added example scripts in examples/.

0.02

    Added or_mask_set.

0.01

    Initial public release.  Should be considered beta, and methods may be
added or changed until the first stable release.

