Package dev.morphia.aggregation.experimental.expressions

Class AccumulatorExpressions

java.lang.Object

dev.morphia.aggregation.experimental.expressions.AccumulatorExpressions

public final class AccumulatorExpressions
extends Object

Defines helper methods for accumulator expressions

Since:

2.0

Method Summary

Modifier and Type	Method	Description
static AccumulatorExpression	accumulator(String initFunction, String accumulateFunction, List<Expression> accumulateArgs, String mergeFunction)	Returns an array of unique expression values for each group.
static Expression	addToSet(Expression value)	Returns an array of unique expression values for each group.
static Expression	avg(Expression value, Expression... additional)	Returns an average of numerical values.
static Expression	first(Expression value)	Returns a value from the first document for each group.
static Expression	function(String body, Expression... args)	Defines a custom aggregation function or expression in JavaScript.
static Expression	last(Expression value)	Returns a value from the last document for each group.
static Expression	max(Expression value)	Returns the highest expression value for each group.
static Expression	min(Expression value)	Returns the lowest expression value for each group.
static Push	push()	Returns an array of all values that result from applying an expression to each document in a group of documents that share the same group by key.
static Expression	push(Expression value)	Returns an array of expression values for each group.
static Expression	stdDevPop(Expression value, Expression... additional)	Returns the population standard deviation of the input values.
static Expression	stdDevSamp(Expression value, Expression... additional)	Returns the sample standard deviation of the input values.
static Expression	sum(Expression first, Expression... additional)	Calculates and returns the sum of numeric values.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Method Detail

accumulator

public static AccumulatorExpression accumulator(String initFunction,
                                                String accumulateFunction,
                                                List<Expression> accumulateArgs,
                                                String mergeFunction)

Returns an array of unique expression values for each group. Order of the array elements is undefined.

Parameters:

initFunction - used to initialize the state. The init function receives its arguments from the initArgs expression.

accumulateFunction - used to accumulate documents. The accumulate function receives its arguments from the current state and accumulateArgs array expression.

accumulateArgs - Arguments passed to the accumulate function.

mergeFunction - used to merge two internal states.

Returns:

the new expression

Since:

2.1

MongoDB documentation

Aggregration Expression: $accumulator

addToSet

public static Expression addToSet(Expression value)

Returns an array of unique expression values for each group. Order of the array elements is undefined.

Parameters:

value - the value

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $addToSet

avg

public static Expression avg(Expression value,
                             Expression... additional)

Returns an average of numerical values. Ignores non-numeric values.

Parameters:

value - the value

additional - any subsequent expressions to include in the expression

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $avg

first

public static Expression first(Expression value)

Returns a value from the first document for each group. Order is only defined if the documents are in a defined order.

Parameters:

value - the value

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $first

function

public static Expression function(String body,
                                  Expression... args)

Defines a custom aggregation function or expression in JavaScript.

Parameters:

body - the function body

args - the function arguments

Returns:

the new expression

Since:

2.1

MongoDB documentation

Aggregration Expression: $function

last

public static Expression last(Expression value)

Returns a value from the last document for each group. Order is only defined if the documents are in a defined order.

Parameters:

value - the value

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $last

max

public static Expression max(Expression value)

Returns the highest expression value for each group.

Parameters:

value - the value

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $max

min

public static Expression min(Expression value)

Returns the lowest expression value for each group.

Parameters:

value - the value

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $min

push

public static Expression push(Expression value)

Returns an array of expression values for each group.

Parameters:

value - the value

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $push

push

public static Push push()

Returns an array of all values that result from applying an expression to each document in a group of documents that share the same group by key.

$push is only available in the $group stage.

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $push

stdDevPop

public static Expression stdDevPop(Expression value,
                                   Expression... additional)

Returns the population standard deviation of the input values.

Parameters:

value - the value

additional - any subsequent expressions to include in the expression

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $stdDevPop

stdDevSamp

public static Expression stdDevSamp(Expression value,
                                    Expression... additional)

Returns the sample standard deviation of the input values.

Parameters:

value - the value

additional - any subsequent expressions to include in the expression

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $stdDevSamp

sum

public static Expression sum(Expression first,
                             Expression... additional)

Calculates and returns the sum of numeric values. $sum ignores non-numeric values.

Parameters:

first - the first expression to sum

additional - any subsequent expressions to include in the sum

Returns:

the new expression

MongoDB documentation

Aggregration Expression: $sum