is
Specifies whether the data source should only act on changes that are explicitly provided to it, rather than having reindex the whole directory. Set this property to true if you are able to specify which changes took place in the documents directory, thus avoiding the overhead of rescanning the directory when indexing. Use with didAddOrModifyDocumentAtPath and didRemoveDocumentAtPath methods. You still need to index the library afterwards with PdfLibrary.updateIndexFromDataSource.