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Standard Functions

org.apache.spark.sql.functions object defines built-in standard functions to work with (values produced by) columns.

You can access the standard functions using the following import statement in your Scala application:

import org.apache.spark.sql.functions._


udaf[IN: TypeTag, BUF, OUT](
  agg: Aggregator[IN, BUF, OUT]): UserDefinedFunction // (1)!
udaf[IN, BUF, OUT](
  agg: Aggregator[IN, BUF, OUT],
  inputEncoder: Encoder[IN]): UserDefinedFunction
  1. Uses an ExpressionEncoder of IN type

udaf creates a UserDefinedAggregator with the given Aggregator and Encoder.

Creating AggregateExpression for AggregateFunction

  func: AggregateFunction,
  isDistinct: Boolean = false): Column

withAggregateFunction requests the given AggregateFunction expression to toAggregateExpression (with the given isDistinct flag).

In the end, withAggregateFunction creates a Column for the AggregateExpression.