Aggregation

Aggregation definition

Aggregation performs in three steps: map-reduce-postMap. For example, we'd like to count all letters in a bunch of strings and return value as a string. Then the steps will be:

1. map:

(s: String) => BigInt(s.length)

2. reduce

(a: BigInt, b: BigInt) = a + b

3. postMap

(i: BigInt) => i.toString

T: input type of aggregation

Linear Supertypes

Serializable, Serializable, AnyRef, Any

Type Members

abstract type Interim

Type after first map operation
abstract type Out

Output type

Abstract Value Members

abstract val dataType: Aux[Out]

Output data type
abstract def emptyValue(implicit a: Aggregations): Option[Out]

Default empty aggregation value
abstract def map(t: T)(implicit a: Aggregations): Interim

Map input value of type T to Interim type
Map input value of type T to Interim type
t
value to be mapped
a
instance of aggregations implementation
returns
mapped value
abstract val name: String

This aggregation name
abstract def postMap(x: Interim)(implicit a: Aggregations): Out

Converts reduced value of type Interim to output type
Converts reduced value of type Interim to output type
x
value to be converted
a
instance of aggregations implementation
returns
converted value
abstract def reduce(x: Interim, y: Interim)(implicit a: Aggregations): Interim

Reduces two mapped values into one value
Reduces two mapped values into one value
x
first value
y
second value
a
instance of aggregations implementation
returns
reduced value

Concrete Value Members

final def !=(arg0: Any): Boolean

Definition Classes
AnyRef → Any
final def ##(): Int

Definition Classes
AnyRef → Any
final def ==(arg0: Any): Boolean

Definition Classes
AnyRef → Any
final def asInstanceOf[T0]: T0

Definition Classes
Any
def clone(): AnyRef

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( ... )
final def eq(arg0: AnyRef): Boolean

Definition Classes
AnyRef
def equals(arg0: Any): Boolean

Definition Classes
AnyRef → Any
def finalize(): Unit

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] )
final def getClass(): Class[_]

Definition Classes
AnyRef → Any
def hashCode(): Int

Definition Classes
AnyRef → Any
final def isInstanceOf[T0]: Boolean

Definition Classes
Any
final def ne(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def notify(): Unit

Definition Classes
AnyRef
final def notifyAll(): Unit

Definition Classes
AnyRef
final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
def toString(): String

Definition Classes
AnyRef → Any
final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )

Related Docs: object Aggregation | package types

trait Aggregation[T] extends Serializable

Type Members

abstract type Interim

abstract type Out

Abstract Value Members

abstract val dataType: Aux[Out]

abstract def emptyValue(implicit a: Aggregations): Option[Out]

abstract def map(t: T)(implicit a: Aggregations): Interim

abstract val name: String

abstract def postMap(x: Interim)(implicit a: Aggregations): Out

abstract def reduce(x: Interim, y: Interim)(implicit a: Aggregations): Interim

Concrete Value Members

final def !=(arg0: Any): Boolean

final def ##(): Int

final def ==(arg0: Any): Boolean

final def asInstanceOf[T0]: T0

def clone(): AnyRef

final def eq(arg0: AnyRef): Boolean

def equals(arg0: Any): Boolean

def finalize(): Unit

final def getClass(): Class[_]

def hashCode(): Int

final def isInstanceOf[T0]: Boolean

final def ne(arg0: AnyRef): Boolean

final def notify(): Unit

final def notifyAll(): Unit

final def synchronized[T0](arg0: ⇒ T0): T0

def toString(): String

final def wait(): Unit

final def wait(arg0: Long, arg1: Int): Unit

final def wait(arg0: Long): Unit

Inherited from Serializable

Inherited from Serializable

Inherited from AnyRef

Inherited from Any

Ungrouped