title: Union between streaming and batch DataFrames/Datasets in StructuredStream
body: <p>I am trying to make union operation of streaming and batch dataframes. But i am catching the following <strong>error:</strong></p>
  
  <blockquote>
    <p>ERROR Uncaught throwable from user code: org.apache.spark.sql.AnalysisException: Union between streaming and batch DataFrames/Datasets is not supported;;
    Union</p>
  </blockquote>
  
  <p>Is this feature is not supported yet in Struct Stream?</p>
  
  <p>Thanks.</p>