leventov commented on a change in pull request #7293: AggregatorFactory: Clarify methods that return other AggregatorFactories. URL: https://github.com/apache/incubator-druid/pull/7293#discussion_r268344434
########## File path: processing/src/main/java/org/apache/druid/query/aggregation/AggregatorFactory.java ########## @@ -94,20 +94,44 @@ public AggregateCombiner makeNullableAggregateCombiner() } /** - * Returns an AggregatorFactory that can be used to combine the output of aggregators from this factory. This - * generally amounts to simply creating a new factory that is the same as the current except with its input - * column renamed to the same as the output column. + * Returns an AggregatorFactory that can be used to combine the output of aggregators from this factory. It is used + * when we know we have some values that were produced with this aggregator factory, and want to do some additional + * combining of them. This happens, for example, when merging query results from two different segments, or two + * different servers. + * + * The combining factory is often computed by simply creating a new factory that is the same as the current, except Review comment: Doesn't sound quite right to me. E. g. the majority of complex aggregators have different combining factories. ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
