group_by:An optional list of attributes over which the grouping should occur.
aggregations:A list if elements where each element contains up to four string:
- The name of the aggregate function, e.g. MAX
- The input attribute over which the aggregation should be done. This can be a single value like
'price'or for some aggregate function a list \
'*'for all Attributes. The latter one can be used for aggregations where so single attribute is relevant, e.g. with COUNT
- The name of the output attribute for this aggregation
- The optional type of the output. If not given, DOUBLE will be used.
dumpAtValueCount:This parameter is used in the interval approach. Here a result is generated, each time an aggregation cannot be changed anymore. This leads to fewer results with a larger validity. With this parameter the production rate can be raised. A value of 1 means, that for every new element the aggregation operator receives new output elements are generated. This leads to more results with a shorter validity.
outputPA: This parameter allow to dump partial aggregates instead of evaluted values. The partial aggregates can be send to other aggregation operators and do a final aggregation (e.g. in case of distribution). The input schema of an aggregate operator that read partial aggregates must state a datatype that is a partial aggregated (see example below). Remark: Aggregate has one input and requires ordered input. To combine different parital aggregations e.g. a union operator is needed to reorder the input elements.
drainAtDone: Boolean, default true: If done is called, all not already written elements will be written.
drainAtClose: Boolean, default false: If close is called, all not already written elements will be written.
FastGrouping: Use hash code instead of compare to create group. Potentially unsafe!