UDAFRegistration

class UDAFRegistration extends Logging

Provides methods to register a UDAF (user-defined aggregate function) in the Snowflake database.

Session.udaf returns an object of this class.

To register a UDAF, you must:

Define a UDAF class.
Create an instance of that class, and register that instance as a UDAF.

The next sections describe these steps in more detail.

Defining the UDAF Class

Define a class that inherits from one of the UDAF[N] classes (e.g. UDAF1, UDAF2, etc.), where n specifies the number of input arguments for your UDAF. For example, if your UDAF passes in 2 input arguments, extend the UDAF2 class.

In your class, override the following methods:

initialize(), which returns the initial state of the aggregation.
accumulate(), which updates the aggregation state with a new input row.
merge(), which merges two aggregation states into one.
terminate(), which produces the final output value from the aggregation state.
outputType(), which returns a types.DataType object that describes the type of the returned value.

Supported Data Types

Snowflake supports the following data types for the input arguments and return value of a UDAF:

SQL Type	Scala Type	Java Type	Notes
NUMBER	Short or Option[Short]	Short or java.lang.Short	Supported
NUMBER	Int or Option[Int]	Integer	Supported
NUMBER	Long or Option[Long]	Long or java.lang.Long	Supported
FLOAT	Float or Option[Float]	Float or java.lang.Float	Supported
DOUBLE	Double or Option[Double]	Double	Supported
NUMBER	java.math.BigDecimal	java.math.BigDecimal	Supported
VARCHAR	String or java.lang.String	java.lang.String	Supported
BOOL	Boolean or Option[Boolean]	Boolean	Supported
DATE	java.sql.Date	java.sql.Date	Supported
TIME	java.sql.Time	java.sql.Time	Supported
TIMESTAMP	java.sql.Timestamp	java.sql.Timestamp	Supported
BINARY	Array[Byte]	byte[]	Supported
ARRAY	Array[String] or Array[Variant]	String[] or Variant[]	Supported array of type Array[String] or Array[Variant]
OBJECT	Map[String, String] or Map[String, Variant]	Map	For Scala, supported mutable map of type scala.collection.mutable.Map[String, String] or scala.collection.mutable.Map[String, Variant]. For Java, use inputSchema() to specify types.
VARIANT	com.snowflake.snowpark.types.Variant	Variant	Supported

Note: GEOGRAPHY and GEOMETRY types are not supported for UDAF input arguments or return values.

Note: Structured types (ARRAY, OBJECT, MAP with nested types) have limited support. For complex nested structures, consider using VARIANT type and performing conversion in your UDAF code.

Aggregation State Requirements

The aggregation state class must be serializable. To ensure compatibility with Kryo serialization:

For best compatibility: The state class should implement java.io.Serializable and have a public no-arg constructor.
For Scala case classes or classes without no-arg constructors: Kryo uses Objenesis to instantiate objects without calling constructors. This works when the server has Objenesis support enabled.
For custom serialization: Implement java.io.Externalizable for fine-grained control over serialization.

Example of a UDAF Class

The following is an example of a UDAF class that computes the average of integers. The state is a custom class that holds the sum and count.

The UDAF passes in 1 argument, so the class extends UDAF1.

// State class must be Serializable with a no-arg constructor for Kryo deserialization
class AvgState extends Serializable {
    var sum: Long = 0L
    var count: Long = 0L
}

class MyAvgUDAF extends UDAF1[AvgState, Double, Int] {
    override def initialize(): AvgState = new AvgState()
    override def accumulate(state: AvgState, input: Int): AvgState = {
        state.sum += input
        state.count += 1
        state
    }
    override def merge(state1: AvgState, state2: AvgState): AvgState = {
        state1.sum += state2.sum
        state1.count += state2.count
        state1
    }
    override def terminate(state: AvgState): Double = {
        if (state.count == 0) 0.0 else state.sum.toDouble / state.count
    }
    override def outputType(): DataType = DoubleType
}

Registering the UDAF

Next, create an instance of the new class, and register the class by calling one of the UDAFRegistration methods. You can register a temporary or permanent UDAF by name.

Registering a Temporary UDAF By Name

To register a temporary UDAF by name, call registerTemporary, passing in a name for the UDAF and an instance of the UDAF class. For example:

// Use the MyAvgUDAF defined in previous example.
val myAvg = session.udaf.registerTemporary("my_avg", new MyAvgUDAF())
df.select(myAvg(col("a"))).show()

Registering a Permanent UDAF By Name

If you need to use the UDAF in subsequent sessions, register a permanent UDAF.

When registering a permanent UDAF, you must specify a stage where the registration method will upload the JAR files for the UDAF and its dependencies. For example:

val myAvg = session.udaf.registerPermanent("my_avg", new MyAvgUDAF(), "@myStage")
df.select(myAvg(col("a"))).show()

Since: 1.19.0

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new UDAFRegistration(session: Session)

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def registerPermanent(funcName: String, udaf: JavaUDAF, stageLocation: String): AggregateFunction
Registers a Java UDAF instance as a permanent UDAF.
Registers a Java UDAF instance as a permanent UDAF.
funcName
The name of the UDAF.
udaf
The Java UDAF instance.
stageLocation
The stage location to upload JARs.
returns
An AggregateFunction representing the UDAF.
Since
1.19.0
def registerPermanent(funcName: String, udaf: UDAF, stageLocation: String): AggregateFunction
Registers a Scala UDAF instance as a permanent UDAF.
Registers a Scala UDAF instance as a permanent UDAF.
funcName
The name of the UDAF.
udaf
The Scala UDAF instance to be registered.
stageLocation
The stage location to upload JARs.
returns
An AggregateFunction representing the UDAF.
Since
1.19.0
def registerTemporary(funcName: String, udaf: JavaUDAF): AggregateFunction
Registers a Java UDAF instance as a temporary UDAF.
Registers a Java UDAF instance as a temporary UDAF.
funcName
The name of the UDAF.
udaf
The Java UDAF instance.
returns
An AggregateFunction representing the UDAF.
Since
1.19.0
def registerTemporary(udaf: JavaUDAF): AggregateFunction
Registers a Java UDAF instance as a temporary anonymous UDAF that is scoped to this session.
Registers a Java UDAF instance as a temporary anonymous UDAF that is scoped to this session.
udaf
The Java UDAF instance.
returns
An AggregateFunction representing the UDAF.
Since
1.19.0
def registerTemporary(funcName: String, udaf: UDAF): AggregateFunction
Registers a Scala UDAF instance as a temporary UDAF.
Registers a Scala UDAF instance as a temporary UDAF.
funcName
The name of the UDAF.
udaf
The Scala UDAF instance to be registered.
returns
An AggregateFunction representing the UDAF.
Since
1.19.0
def registerTemporary(udaf: UDAF): AggregateFunction
Registers a Scala UDAF instance as a temporary anonymous UDAF that is scoped to this session.
Registers a Scala UDAF instance as a temporary anonymous UDAF that is scoped to this session.
udaf
The Scala UDAF instance to be registered.
returns
An AggregateFunction representing the UDAF.
Since
1.19.0
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def udaf(funcName: String, execName: String = "", execFilePath: String = "")(func: => AggregateFunction): AggregateFunction
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Packages

UDAFRegistration

class UDAFRegistration extends Logging

Defining the UDAF Class

Supported Data Types

Aggregation State Requirements

Example of a UDAF Class

Registering the UDAF

Registering a Temporary UDAF By Name

Registering a Permanent UDAF By Name

Instance Constructors

Value Members

Deprecated Value Members

Inherited from Logging

Inherited from AnyRef

Inherited from Any

Ungrouped

Packages

UDAFRegistration

class UDAFRegistration extends Logging

Defining the UDAF Class

Supported Data Types

Aggregation State Requirements

Example of a UDAF Class

Registering the UDAF

Registering a Temporary UDAF By Name

Registering a Permanent UDAF By Name

Instance Constructors

Value Members

Deprecated Value Members

Inherited from Logging

Inherited from AnyRef

Inherited from Any

Ungrouped

UDAFRegistration