accumulators

Documentation

Overview

Package accumulators provides aggregation accumulator operators. Accumulators are different from other operators as they perform operations on a group of documents rather than a single document. They are used only in small subset of available stages (like `$group`).

Accumulators that can be used outside of accumulation with different behaviour (like `$sum`), should be stored in both operators and accumulators packages.

Index

• Variables
• type Accumulator
  • func NewAccumulator(stage, key string, value any) (Accumulator, error)

Variables

var Accumulators = map[string]newAccumulatorFunc{

	"$count": newCount,
	"$sum":   newSum,
}

Accumulators maps all aggregation accumulators.

Types

type Accumulator

type Accumulator interface {
	// Accumulate documents and returns the result of applying operator.
	// It should always close iterator.
	Accumulate(iter types.DocumentsIterator) (any, error)
}

Accumulator is a common interface for aggregation accumulation operators.

func NewAccumulator

func NewAccumulator(stage, key string, value any) (Accumulator, error)

NewAccumulator returns accumulator for provided value.