+1 to considering "metric" / PMetric / etc. On Wed, Mar 23, 2016 at 8:09 AM, Amit Sela <[email protected]> wrote:
> 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. >> >>
