When a size-based window is processing a lot that contains more than one item, all of the items are processed in the window before any of the rest of the stream query is processed. None of the intermediate states are visible to the query. This means that in the following query:

if the window contains the events A(1), A(2) and A(3) and a lot containing both A(4) and A(5) arrives, those will displace A(1) and A(2) immediately. The state of the window A(2), A(3), A(4) will never have existed. This is more relevant when the lot contains more items than will fit in the window. In this case, if five more events arrived in a single lot, the three events will fall out of the window, the last three events will go into the window and the two interim events will disappear – never having been in the window at any point.

This behavior means that care must be taken with fixed-size windows when events might be processed in lots.