uniqueidentifier - How to set a field to keep a row unique in lucene? - Stack Overflow

This is exactly the purpose of the IndexWrite#updateDocument method. The first argument is the term that must be unique in your index.

For example,

String id = "42";  Document doc = new Document();  Field field = new Field("id", id, Store.YES, Index.NOT_ANALYZED);  doc.add(field);    indexWriter.updateDocument(new Term("id", id), doc);  

will ensure that doc is the only document with id 42 in your index.

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