Applies a reduce function to the window. The window function is called for each evaluation of the window for each
key individually. The output of the reduce function is interpreted as a regular non-windowed stream.
Applies a reduce function to the window. The window function is called for each evaluation of the window for each
key individually. The output of the reduce function is interpreted as a regular non-windowed stream.
This window will try and pre-aggregate data as much as the window policies permit. For example,tumbling time
windows can perfectly pre-aggregate the data, meaning that only one element per key is stored. Sliding time
windows will pre-aggregate on the granularity of the slide interval, so a few elements are stored per key (one per
slide interval). Custom windows may not be able to pre-aggregate, or may need to store extra values in an
aggregation tree.
Attributes
function
The reduce function.
Returns:
The data stream that is the result of applying the reduce function to the window.