Gather Streams
The Gather Streams logical operator is only used in parallel query plans. The Gather Streams operator consumes several input streams and produces a single output stream of records by combining the input streams. The record contents and format are not changed. If this operator is order-preserving, then all input streams must be ordered.
If the output is ordered, then the Argument column contains an ORDER BY:() predicate and the names of columns being ordered.