DeclarativeAggregate Contract — Unevaluable Aggregate Function Expressions

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

Note
 An unevaluable expression cannot be evaluated to produce a value (neither in interpreted nor code-generated expression evaluations) and has to be resolved (replaced) to some other expressions or logical operators at analysis or optimization phases or they fail analysis.
Table 1. DeclarativeAggregate Contract
Property Description

evaluateExpression

 
evaluateExpression: Expression

The expression that returns the final value for the aggregate function

Used when:

initialValues

 
initialValues: Seq[Expression]

mergeExpressions

 
mergeExpressions: Seq[Expression]

updateExpressions

 
updateExpressions: Seq[Expression]
Table 2. DeclarativeAggregates (Direct Implementations)
DeclarativeAggregate Description

AggregateWindowFunction

Contract for declarative window aggregate function expressions

Average

CentralMomentAgg

Corr

Count

Covariance

First

Last

Max

Min

SimpleTypedAggregateExpression

Sum

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