Coalesce operator

This Operator can be used to combine sequent elements, e.g. by a set of grouping attributes or with a predicates.

In the attributes case, the elements are merged with also given aggregations functions, as long as the grouping attributes (e.g. a sensorid) are the same. When a new group is opened (e.g. a measurement from a new sensor) the old aggregates values and the grouping attributes are created as a result.

In the predicate case, the elements are merged as long as the predicates evaluates to false, i.e. a new tuple is created when the predicates evaluates to true. If you want to aggregate as long, as the predicate is true, simply use !(predicate) as predicate.

Parameter

• AGGREGATIONS: The aggregate functions (see AGGREGATE for examples)
• ATTR: The grouping attributes, cannot be used together with predicate.
• PREDICATE: The predicate cannot be used together with ATTR

Example

coalesce = COALESCE({ATTR=['sensorid'], 
        AGGREGATIONS=[['AVG','temperature','temperatur']},tempSensor1)

coalesce = COALESCE({predicate='temperature>=10', 
        AGGREGATIONS=[['last','temperature','temperature'], ['AVG,'temperature','avgTemp']},tempSensor1)