Package org.apache.spark.sql.connector.catalog.functions

Interface Reducer<I,O>

Type Parameters:

I - the physical Java type of the input

O - the physical Java type of the output

@Evolving
public interface Reducer<I,O>

A 'reducer' for output of user-defined functions.

Since:

4.0.0

See Also:

• A user defined function f_source(x) is 'reducible' on another user_defined function f_target(x) if
  • There exists a reducer function r(x) such that r(f_source(x)) = f_target(x) for all input x, or
  • More generally, there exists reducer functions r1(x) and r2(x) such that r1(f_source(x)) = r2(f_target(x)) for all input x.
  where = means both value and data type match.

Method Summary

Modifier and Type	Method	Description
default String	displayName()	Returns a short string representation for plan display (e.g.
O	reduce(I arg)
DataType	resultType()	Returns the data type of values produced by this reducer.

Method Details

reduce

O reduce(I arg)

displayName

default String displayName()

Returns a short string representation for plan display (e.g. explain output). Defaults to the unqualified class name; implementations may override for a richer description.

resultType

DataType resultType()

Returns the data type of values produced by this reducer.

Returns:

the data type of values produced by this reducer.