presto-main/src/main/java/io/prestosql/sql/planner/optimizations/BeginTableWrite.java/BeginTableWrite/getMaterializedHandle
class BeginTableWrite:        public Optional<WriterTarget> getMaterializedHandle(WriterTarget handle)
        {
            checkState(this.handle.get().equals(handle), "can't find materialized handle for WriterTarget");
            return materializedHandle;
        }