To generate a lot that contains multiple items, a stream query must specify a simple projection or an aggregate projection that contains a group by clause. The stream query must also either receive lots that contain multiple items or must contain one of the following:

A query with a non-grouped aggregate projection never generates multiple items. It generates a single item or nothing.

A timed window with the rstream keyword can generate lots because multiple items can have the same timestamp. In a timed window, when items with the same timestamp expire they all leave the window at the same time. However, the correlator still maintains the order in which the items were generated or received.