Luacene

Luacene is a Lua binding for the C++ implementation of Lucene - CLucene.

It is not meant to be a complete binding (better use something like SWIG for that), but just a handful of classes and functions that are most needed (for me at least :).

It tries to do thing Lua way - i.e. a Document with Fields is just a Lua table with keys, Hits instance has custom __index etc.

Luacene was written for the 2_3_2 git master HEAD version of CLucene.

Luacene uses the ANSI mbstowcs and wcstombs functions for Lua <-> Unicode conversion. They depend on the current locale, specifically on the LC_CTYPE settings, i.e. for Utf8, you should check the output of the locale command (I have: LC_CTYPE="en_US.UTF-8"), or modify it through os.setlocale.

Overview

Library is loaded using require:

require 'luacene'

The luacene table has two functions:

• luacene.writer(path [, stopwords]) - returns an IndexWriter for the specified path.
• luacene.searcher(path [, stopwords]) - returns an IndexSearcher for the specified path.

RAMDirectory is not supported (yet). Both use the StandardAnalyzer tokenizer. stopwords is an optional Lua table (array) containing strings, which are used as stopwords for the analyzer. If no table is provided, the default set of English stopwords is used.

IndexWriter has these functions:

• IndexWriter:addDocument(doc)

  Adds a document doc to the index. doc is a Lua table with string keys. These keys are interpreted as Field names. Values can be:

  • string - the text is stored as field value as Field::STORE_YES | Field::INDEX_TOKENIZED (a sensible default)
  • table - must be of this structure { value, store, index, termvector }
    • value - field text
    • store - "yes", "no", "compress"
    • index - "no", "tokenized", "untokenized", "nonorms"
    • termvector - "no", "yes", "positions", "offsets", "positions+offsets"

• IndexWriter:optimize()

  Optimizes the index. Returns true when everything went OK, or nil, error in case of error.

• IndexWriter:flush()

  Flushes the index. Returns true when everything went OK, or nil, error in case of error.

IndexSearcher has one method:

• IndexSearcher:search(query)

  Searches the index for query. The query is a string, which is parsed by QueryParser. Returns an instance of Hits. Uses "contents" as default field name.

Hits is the search result set. It has overriden __index, so that access to documents is straight-forward.

• Hits.lenght - the number of search results

• Hits[i] - retrieves the i-th document. i is one based, like tables in Lua (1 <= i <= Hits.lenght). Documents are returned as Lua tables, with keys being Field names and values being their string content, which is encoded using current locale.

License

Copyright (c) 2010 Michal Kottman

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.