Revision history for Perl extension DBIx::TextIndex.

=head1 CHANGES

=head2 0.28

No changes, updated contact info

=head2 0.27

Fixed POD coverage test error

=head2 0.26

Fixed problem with re-indexing a document several times with SQLite (rt.cpan.org #16247)

Stoplists now work with QueryParser

unscored_search() was returning internal document ids instead of keys

Fixed table_exists() in case schema name is prefixed to table name in results of DBI->tables() call

=head2 0.25

New methods indexed() and last_indexed_key()

Removed a few stray print statements

=head2 0.24

WARNING: indexes must be recreated, format has changed

Ability to reindex existing documents

New methods add(), begin_add(), commit_add() with support for arbitrary keys and indexing of data from sources other than a database table

Made individual database drivers subclasses of DBIx::TextIndex::DBD for easier porting. A new driver can override selected database-specific methods instead of having to rewrite all methods.

Check for division by zero in resolveplural()

Bug fix for pathological case where only query term is a NOT term

=head2 0.23

SQLite support

Changed wildcard syntax slightly: a '?' character matches any single character. A '+' at the end of a word behaves like the '?' character in previous versions, matching the singular or plural forms of the word.

Wildcard characters '*' and '?' can now be used in the middle of a query term, as well as at the end of a query term.

Added error messages error_wildcard_length and error_wildcard_expansion, collection table will be upgraded

Added argument 'max_wildcard_term_expansion' to new(). This specifies the maximum number of words a wildcard term can expand to before throwing an exception. The default is 30 words.

Fixed incorrect results for Okapi-scored results with wildcard terms

Fixed segfault if position index structure is corrupted

Fixed bug occurring when add_doc() is followed by search() on same instance of $index

=head2 0.22

WARNING: indexes must be recreated from scratch. Rewrote proximity index code from scratch using XS. New index format is faster, more compact, and scaleable. Flag proximity_index now defaults to 1.

Removed legacy_tf_idf scoring method.

Fixed division-by-zero error with wildcard searches

Added support for PostgreSQL

=head2 0.21

Fixed bug where proximity search was case-sensitive instead of case-insensitive

Fixed problem where some punctuation characters in query were treated as query terms instead of ignoring the characters

=head2 0.20

Added inline fielded queries, e.g.: $index->search( field1 => 'field2:this field3:"that phrase" foo bar' ); In previous version, this search could only be represented like this: $index->search( field1 => 'foo bar',

                    field2 => 'this',
                    field3 => '"that phrase"');

The advantage of the new syntax is that fields can be combined in arbitary boolean expressions, where previously only the union of the fields was returned. For example:

(field1:this OR field2:that) AND (field3:"foo bar" OR field1:foo)

Wild and plural search bug fixes

Turned proximity search back on, changed syntax. For example, to find "foo" followed by "bar" with 0, 1 or 2 words between:

"foo bar"~3

=head2 0.19

Rewrote query parser. Now we support nested subqueries in parentheses, AND/OR/NOT operators, and existing '+/-' operators (this OR that) AND (foo OR bar) +"this phrase" -"not this phrase"

Changed prefix query syntax slightly: '' is now prefix operator, '?' is plural operator:

      dog  matches dog, dogs, dogma, dogmatic, dogmatically
      cat?  matches cat, cats

Rewrote critical loop of Okapi scoring as XSUB. Search over large collections is much faster.

=head2 0.18

Fixed bug where Okapi function did not score multiple fields

Tweaks to improve boolean search performance.

Added periodic flush of hash tables caches to save memory in long-running instances.

Used a more compact represention of docweights, index needs to be recreated.

=head2 0.17

Reduced memory usage by TermDocsCache

Implemented Okapi BM25 weighting function [S.E. Robertson et al., Google for description] for scoring documents. Pass scoring_method => 'legacy_tfidf' to new() or search() to use older method. Thanks to the lucy project (http://www.seg.rmit.edu.au/lucy/) for inspiration.

Added docweights table to support Okapi BM25 scoring. Indexes need to be dropped and recreated.

Pass "update_commit_interval" to new() to control memory usage in index updates. As the index is built, postings lists are built up in memory; this parameter controls the number of documents held in memory before being flushed to the database. Default is 20000. To disable, pass 0, and all documents passed to add_doc() will indexed in memory before writing to the database.

Fixed problem with inaccurate search results if multiple searches were performed on a single instance while another instance was updating index.

=head2 0.16

Added XSUB pack_term_docs_append_vint to speed up commitdocs when adding new postings to existing compressed postings

=head2 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

=head2 0.14

Fixed memory leak in integer decoding

=head2 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. This format is similar to the format in Lucene (http://jakarta.apache.org/lucene/).

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.

=head2 0.12

Added optimizeor_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.

=head2 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.

=head2 0.10

Fixed collection table upgrade bug

=head2 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).

=head2 0.08

Bug fix: add_mask() was not inserting masks

=head2 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: storecollection_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

=head2 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 invertedremove() 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 highlighting 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:

NOTE: tripie proximity index is replaced with newer compact index structure as of version 0.22
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"

  NOTE: as of version 0.20, this syntax has changed: "some phrase"~3

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

=head2 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.

=head2 0.04

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

Changed booleancompare() and phrasesearch() 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().

=head2 0.03

Added example scripts in examples/.

=head2 0.02

Added or_mask_set.

=head2 0.01

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

=cut