How about "PMetric" ? On Wed, Mar 23, 2016, 16:53 Frances Perry <[email protected]> wrote:
> >>> Perhaps I'm unclear on what an “Aggregator” is. I assumed that a line >>> such as the following: >>> >>> PCollection<KV<String, Double>> meanByName = >>> dataPoints.apply(Mean.<String, Double>perKey()); >>> >>> …would be considered an Aggregator, since it applies a mean aggregation >>> over a window. Is that correct, with respect to the Beam terminology? If >>> not, what would an example of an Aggregator be? >>> >> > Ah, we may have some slightly confusing terminology here. > > In that code snippet you are using a PTransform (Mean.perKey) to combine > a PCollection using the Mean CombineFn > <https://github.com/apache/incubator-beam/blob/c199f085473cfcd79014d0a022b5ce3fdd4863ec/sdk/src/main/java/com/google/cloud/dataflow/sdk/transforms/Combine.java#L359>. > An Aggregator > <https://github.com/apache/incubator-beam/blob/211e76abf9ba34c35ef13cca279cbeefdad7c406/sdk/src/main/java/com/google/cloud/dataflow/sdk/transforms/Aggregator.java#L54> > takes a CombineFn and applies it continuously within a DoFn. So it's more > analogous to a 'counter'. You can see an example of aggregators in > DebuggingWordCount > <https://github.com/apache/incubator-beam/blob/master/examples/src/main/java/com/google/cloud/dataflow/examples/DebuggingWordCount.java#L129> > . > > We never really used the term *aggregation *to refer to a general set of > PTransforms until we started describing things to the community. But it is > a useful word, so we've ended up in a bit of confusing state. Maybe we > should consider renaming Aggregator? Something like "metric" might be > clearer. > >
