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Transforms for computing the sum of the elements in a collection, or the sum of the values associated with each key in a collection of key-value pairs.


Example 1: get the sum of a PCollection of Doubles.

PCollection<Double> input = ...;
PCollection<Double> sum = input.apply(Sum.doublesGlobally());

Example 2: calculate the sum of the Integers associated with each unique key (which is of type String).

PCollection<KV<String, Integer>> input = ...;
PCollection<KV<String, Integer>> sumPerKey = input