DeclarativeAggregate — Unevaluable Aggregate Function Expressions¶

DeclarativeAggregate is an extension of the AggregateFunction abstraction for aggregate function expressions that are unevaluable and use expressions for evaluation.

Contract¶

evaluateExpression¶

evaluateExpression: Expression

Expression to calculate the final value of this aggregate function

Used when:

• EliminateAggregateFilter logical optimization is executed
• AggregatingAccumulator utility is used to create an AggregatingAccumulator
• AggregationIterator is requested for the generateResultProjection
• HashAggregateExec physical operator is requested to doProduceWithoutKeys and generateResultFunction
• AggregateProcessor is created

initialValues¶

initialValues: Seq[Expression]

Expression for initial values of this aggregate function

Used when:

• EliminateAggregateFilter logical optimization is executed
• AggregatingAccumulator utility is used to create an AggregatingAccumulator
• AggregationIterator is created
• HashAggregateExec physical operator is requested to doProduceWithoutKeys, createHashMap and getEmptyAggregationBuffer
• HashMapGenerator is created
• AggregateProcessor is created

mergeExpressions¶

mergeExpressions: Seq[Expression]

updateExpressions¶

updateExpressions: Seq[Expression]

Implementations¶

• AggregateWindowFunction
• Average
• BitAggregate
• CentralMomentAgg
• Count
• Covariance
• First
• Last
• Max
• MaxMinBy
• Min
• PearsonCorrelation
• Product
• SimpleTypedAggregateExpression
• Sum
• UnevaluableAggregate