Examples of org.apache.lucene.index.UpgradeIndexMergePolicy

• org.apache.lucene.index.UpgradeIndexMergePolicy
  This {@link MergePolicy} is used for upgrading all existing segments ofan index when calling {@link IndexWriter#optimize()}. All other methods delegate to the base {@code MergePolicy} given to the constructor.This allows for an as-cheap-as possible upgrade of an older index by only upgrading segments that are created by previous Lucene versions. Optimize does no longer really optimize it is just used to "optimize" older segment versions away.

  In general one would use {@link IndexUpgrader}, but for a fully customizeable upgrade, you can use this like any other {@code MergePolicy} and call {@link IndexWriter#optimize()}:

   IndexWriterConfig iwc = new IndexWriterConfig(Version.LUCENE_XX, new KeywordAnalyzer()); iwc.setMergePolicy(new UpgradeIndexMergePolicy(iwc.getMergePolicy())); IndexWriter w = new IndexWriter(dir, iwc); w.optimize(); w.close(); 

  Warning: This merge policy may reorder documents if the index was partially upgraded before calling optimize (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 optimize instead. Please note, the delegate {@code MergePolicy} may also reorder documents. @lucene.experimental @see IndexUpgrader

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