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.
Value parameters
function
The reduce function.
Attributes
Returns
The data stream that is the result of applying the reduce function to the window.