Release 2.0 will primarily make incompatible API improvements.
Release Migration Plan
Immediately prior to release 2.0 will be release 1.9, which will include all of the new 2.0 APIs, and all of the now-deprecated 1.x API's. 2.0 will be identical to 1.9, but with all deprecated APIs removed. To port an application to 2.0 one should first compile it against 1.9. Once it compiles against 1.9 without deprecation warnings, it should be 2.0 compatible.
DONE: Replace Field factory methods (Field.Text, Field.Keyword, etc.) with a few methods that use type-safe enumerations, as described in: http://firstname.lastname@example.org/msg08479.html
DONE: Similarly, replace BooleanQuery.add() with a type-safe enumeration, also as described in: http://email@example.com/msg08479.html
DONE: Replace public IndexWriter fields (mergeFactor, minMergeDocs, etc.) with get/set accessors. Also, minMergeDocs should be renamed maxBufferedDocs.
DONE: Rename InputStream to IndexInput and OutputStream to IndexOutput. Also add BufferedIndexInput and BufferedIndexOutput as the implementation used by FSDirectory, RAMDirectory, etc. This would permit unbuffered and native implementations (e.g., that use mmap) that could potentially speed things considerably.
- DONE: Move language-specific analyzers into separate downloads. Also move analysis/de/WordlistLoader.java one level upwards, as it's not specific to German at all.
Remove public PrintStream infoStream from IndexWriter. Instead use some kind of Logger which is customizable through the API to print debug, error and warning messages within lucene. The logger must not be an external library like log4j, it could be a small implementation directly in lucene to avoid references to external packages.
DONE: Add a non-static method isCurrent() to IndexReader and remove static getCurrentVersion() and lastModified methods: http://firstname.lastname@example.org/msg06143.html (however, the deprecated methods will probably not be removed)
(Hard) Make indexing more flexible, so that one could e.g., not store positions or even frequencies, or alternately, to store extra information with each position, or to even use different posting compression algorithms. This could be implemented by extending Field to specify a FieldIndexer. A FieldIndexer would be passed each token and decide what about it to record, how to record it, etc. All fields with the same name must use the same FieldIndexer implementation. The FieldIndexer implementation would be serialized with the index. Detailed specification of a FieldIndexer API is required before this proposal can be seriously considered.
DONE: Modify MultiFieldQueryParser so that it behaves as most people expect: searching for A AND B in the fields body, title means that both terms must occur, but it doesn't matter whether they occur in title or body. The old behaviour must still be available by default so we stay compatible.
Deprecate PorterStemFilter, in favor of the Snowball analyzers. This should also coincide with folding the Snowball codebase into the main Lucene CVS tree (to be built as a separate JAR but released with the main Lucene distributions).
Here's a list of planned changes that either don't affect the API or that can be implemented in an API compatible way:
- Add support for span queries to query parser?
Implement a callback interface for processes which can run for several minutes like IndexWriter.optimize(). The idea is to define a simple public interface which can be implemented by developers using lucene. The object implementing the callback, could be passed to methods like optimize() and can inform the caller when one of the steps to process has finished. This would make it much easier in interactive applications to inform the user that the system is working and not frozen.
Separate Query.toString from the actual conversion to a string representation. This will allow custom query parsing implementations to provide their own syntax easily. This could be done using an abstract factory that is looked up from each Query.toString implementation, with the current syntax being provided by QueryParser somehow.
Lucene 2.0 was released 2006-05-26. Items not marked with "DONE" above did not make it into the release.