Method DeleteAll

Delete all documents in the index.

This method will drop all buffered documents and will remove all segments from the index. This change will not be visible until a Commit() has been called. This method can be rolled back using Rollback().

NOTE: this method is much faster than using DeleteDocuments(new MatchAllDocsQuery()). Yet, this method also has different semantics compared to DeleteDocuments(Query) / DeleteDocuments(Query[]) since internal data-structures are cleared as well as all segment information is forcefully dropped anti-viral semantics like omitting norms are reset or doc value types are cleared. Essentially a call to DeleteAll() is equivalent to creating a new IndexWriter with CREATE which a delete query only marks documents as deleted.

NOTE: this method will forcefully abort all merges in progress. If other threads are running ForceMerge(Int32), AddIndexes(IndexReader[]) or ForceMergeDeletes() methods, they may receive MergePolicy.MergeAbortedExceptions.