Class IndexUpgrader

This is an easy-to-use tool that upgrades all segments of an index from previous Lucene versions to the current segment file format. It can be used from command line:

 java -cp lucene-core.jar Lucene.Net.Index.IndexUpgrader [-delete-prior-commits] [-verbose] indexDir

Alternatively this class can be instantiated and Upgrade() invoked. It uses UpgradeIndexMergePolicy and triggers the upgrade via an ForceMerge(Int32) request to IndexWriter.

This tool keeps only the last commit in an index; for this reason, if the incoming index has more than one commit, the tool refuses to run by default. Specify -delete-prior-commits to override this, allowing the tool to delete all but the last commit. From .NET code this can be enabled by passing true to IndexUpgrader(Directory, LuceneVersion, TextWriter, Boolean).

Warning: this tool may reorder documents if the index was partially upgraded before execution (e.g., documents were added). If your application relies on "monotonicity" of doc IDs (which means that the order in which the documents were added to the index is preserved), do a full ForceMerge instead. The MergePolicy set by IndexWriterConfig may also reorder documents.