In some situations it is interesting to group the results of the historic process instance query by variable value. Examples:

• return (counts, list) for process instances grouped by values of the variable COUNTRY
• return (counts, list) for process instances grouped by values of the variable TAX RATE
• return (counts, list) for process instances grouped by values of the variable GENDER

In most cases, we believe that users are most interesed in counts but there are situations where a list is requested.

A first iteration can be to provide this feature at the Java + REST API level.

Additional thoughts:

• this has a reporting / Optimize dimension to it but the usecase is not always reporting. The feature is valuable in non-reporting usecases like providing views to task workers.
• While the feature is requested for the (historic) process instance query, a similar case can be made for (historic) user tasks
• performance?