UserDefinedFunction¶

UserDefinedFunction represents a user-defined function.

UserDefinedFunction is <> when:

• udf function is executed

• UDFRegistration is requested to register a Scala function as a user-defined function (in FunctionRegistry)

import org.apache.spark.sql.functions.udf
val lengthUDF = udf { s: String => s.length }

scala> :type lengthUDF
org.apache.spark.sql.expressions.UserDefinedFunction

val r = lengthUDF($"name")

scala> :type r
org.apache.spark.sql.Column

UserDefinedFunction can have an optional <>.

val namedLengthUDF = lengthUDF.withName("lengthUDF")
scala> namedLengthUDF($"name")
res2: org.apache.spark.sql.Column = UDF:lengthUDF(name)

UserDefinedFunction is nullable by default, but can be changed as <>.

[source, scala]¶

val nonNullableLengthUDF = lengthUDF.asNonNullable assert(nonNullableLengthUDF.nullable == false)

[[deterministic]] UserDefinedFunction is deterministic <<_deterministic, by default>>, i.e. produces the same result for the same input. UserDefinedFunction can be changed to be <>.

[source, scala]¶

assert(lengthUDF.deterministic) val ndUDF = lengthUDF.asNondeterministic assert(ndUDF.deterministic == false)

[[internal-registries]] .UserDefinedFunction's Internal Properties (e.g. Registries, Counters and Flags) [cols="1m,3",options="header",width="100%"] |=== | Name | Description

| _deterministic a| [[_deterministic]] Flag that controls whether the function is <> (true) or not (false).

Default: true

• Use <> to change it to false

Used when UserDefinedFunction is requested to <>

|===

=== [[apply]] Executing UserDefinedFunction (Creating Column with ScalaUDF Expression) -- apply Method

apply(
  exprs: Column*): Column

apply creates a Column with ScalaUDF expression.

import org.apache.spark.sql.functions.udf
scala> val lengthUDF = udf { s: String => s.length }
lengthUDF: org.apache.spark.sql.expressions.UserDefinedFunction = UserDefinedFunction(<function1>,IntegerType,Some(List(StringType)))

scala> lengthUDF($"name")
res1: org.apache.spark.sql.Column = UDF(name)

apply is used when...FIXME

=== [[asNonNullable]] Marking UserDefinedFunction as NonNullable -- asNonNullable Method

[source, scala]¶

asNonNullable(): UserDefinedFunction¶

asNonNullable...FIXME

asNonNullable is used when...FIXME

=== [[withName]] Naming UserDefinedFunction -- withName Method

[source, scala]¶

withName(name: String): UserDefinedFunction¶

withName...FIXME

NOTE: withName is used when...FIXME

Creating Instance¶

UserDefinedFunction takes the following when created:

• [[f]] A Scala function (as Scala's AnyRef)
• [[dataType]] Output data type
• [[inputTypes]] Input data types (if available)

UserDefinedFunction initializes the <>.