KeepOnlyOneAggregationFunction

This aggregator can be used as follows:

• On Copper, with .custom(KeepOnlyOneAggregationFunction.PLUGIN_KEY)
• On post-processors that have a reduce stage, with pp.withProperty(DYNAMIC_AGGREGATION_PARAM_AGGREGATION_FUNCTION, KeepOnlyOneAggregationFunction.PLUGIN_KEY).

This aggregator can’t be used on an aggregated measure as it does not implement the disaggregate feature.

This aggregator will return the same value as input only if there is a unique, single input value. If there is no input value or there are multiple input values, the return is null.

Example

The aggregator defined here

Copper.measure("Metric")
        .per("Level")
        .custom(KeepOnlyOneAggregationFunction.PLUGIN_KEY)

will return the following, depending on the aggregation levels:

Only one level aggregation

Multiple-level aggregation