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AggUtils Utility

AggUtils is an utility for Aggregation execution planning strategy.

planAggregateWithoutDistinct

planAggregateWithoutDistinct(
  groupingExpressions: Seq[NamedExpression],
  aggregateExpressions: Seq[AggregateExpression],
  resultExpressions: Seq[NamedExpression],
  child: SparkPlan): Seq[SparkPlan]

planAggregateWithoutDistinct is a two-step physical operator generator.

planAggregateWithoutDistinct first creates an aggregate physical operator with aggregateExpressions in Partial mode (for partial aggregations).

Note

requiredChildDistributionExpressions for the aggregate physical operator for partial aggregation "stage" is empty.

In the end, planAggregateWithoutDistinct creates another aggregate physical operator (of the same type as before), but aggregateExpressions are now in Final mode (for final aggregations). The aggregate physical operator becomes the parent of the first aggregate operator.

Note

requiredChildDistributionExpressions for the parent aggregate physical operator for final aggregation "stage" are the Attributes of the groupingExpressions.

planAggregateWithOneDistinct

planAggregateWithOneDistinct(
  groupingExpressions: Seq[NamedExpression],
  functionsWithDistinct: Seq[AggregateExpression],
  functionsWithoutDistinct: Seq[AggregateExpression],
  resultExpressions: Seq[NamedExpression],
  child: SparkPlan): Seq[SparkPlan]

planAggregateWithOneDistinct...FIXME

Creating Physical Operator for Aggregation

createAggregate(
  requiredChildDistributionExpressions: Option[Seq[Expression]] = None,
  groupingExpressions: Seq[NamedExpression] = Nil,
  aggregateExpressions: Seq[AggregateExpression] = Nil,
  aggregateAttributes: Seq[Attribute] = Nil,
  initialInputBufferOffset: Int = 0,
  resultExpressions: Seq[NamedExpression] = Nil,
  child: SparkPlan): SparkPlan

createAggregate creates a physical operator for the given AggregateExpressions in the following order:

  1. Selects HashAggregateExec for AggregateExpressions with AggregateFunctions with aggBufferAttributes supported

  2. Selects ObjectHashAggregateExec when the following all hold:

  3. SortAggregateExec

createAggregate is used when: