spark技术分享AggregateWindowFunction Contract — Declarative Window Aggregate Function Expressions
AggregateWindowFunction is the extension of the DeclarativeAggregate Contract for declarative aggregate function expressions that are also WindowFunction expressions.
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package org.apache.spark.sql.catalyst.expressions abstract class AggregateWindowFunction extends DeclarativeAggregate with WindowFunction { self: Product => // No required properties (vals and methods) that have no implementation } |
AggregateWindowFunction uses IntegerType as the data type of the result of evaluating itself.
AggregateWindowFunction is nullable by default.
As a WindowFunction expression, AggregateWindowFunction uses a SpecifiedWindowFrame (with the RowFrame frame type, the UnboundedPreceding lower and the CurrentRow upper frame boundaries) as the frame.
AggregateWindowFunction is a DeclarativeAggregate expression that does not support merging (two aggregation buffers together) and throws an UnsupportedOperationException whenever requested for it.
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Window Functions do not support merging. |
| AggregateWindowFunction | Description |
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Window functions that require the size of the current window for calculation |
