http://www.mongodb.org: The Java operations layer for the MongoDB Java Driver. Third parties can wrap this layer to provide custom higher-level APIs
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/*
 * Copyright 2008-present MongoDB, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.mongodb.client.model;


Builders for accumulators used in the group pipeline stage of an aggregation pipeline.

@mongodb.driver.manualcore/aggregation-pipeline/ Aggregation pipeline
@mongodb.driver.manualreference/operator/aggregation/group/#accumulator-operator Accumulators
@mongodb.driver.manualmeta/aggregation-quick-reference/#aggregation-expressions Expressions
@mongodb.server.release2.2
Since:3.1
/**
 * Builders for accumulators used in the group pipeline stage of an aggregation pipeline.
 *
 * @mongodb.driver.manual core/aggregation-pipeline/ Aggregation pipeline
 * @mongodb.driver.manual reference/operator/aggregation/group/#accumulator-operator Accumulators
 * @mongodb.driver.manual meta/aggregation-quick-reference/#aggregation-expressions Expressions
 * @mongodb.server.release 2.2
 * @since 3.1
 */
public final class Accumulators {

    
Gets a field name for a $group operation representing the sum of the values of the given expression when applied to all members of
the group.

Params:
  • fieldName – the field name
  • expression – the expression
Type parameters:
Returns:the field
@mongodb.driver.manualreference/operator/aggregation/sum/ $sum
/**
     * Gets a field name for a $group operation representing the sum of the values of the given expression when applied to all members of
     * the group.
     *
     * @param fieldName the field name
     * @param expression the expression
     * @param <TExpression> the expression type
     * @return the field
     * @mongodb.driver.manual reference/operator/aggregation/sum/ $sum
     */
    public static <TExpression> BsonField sum(final String fieldName, final TExpression expression) {
        return accumulator("$sum", fieldName, expression);
    }

    
Gets a field name for a $group operation representing the average of the values of the given expression when applied to all
members of the group.

Params:
  • fieldName – the field name
  • expression – the expression
Type parameters:
Returns:the field
@mongodb.driver.manualreference/operator/aggregation/avg/ $avg
/**
     * Gets a field name for a $group operation representing the average of the values of the given expression when applied to all
     * members of the group.
     *
     * @param fieldName the field name
     * @param expression the expression
     * @param <TExpression> the expression type
     * @return the field
     * @mongodb.driver.manual reference/operator/aggregation/avg/ $avg
     */
    public static <TExpression> BsonField avg(final String fieldName, final TExpression expression) {
        return accumulator("$avg", fieldName, expression);
    }

    
Gets a field name for a $group operation representing the value of the given expression when applied to the first member of
the group.

Params:
  • fieldName – the field name
  • expression – the expression
Type parameters:
Returns:the field
@mongodb.driver.manualreference/operator/aggregation/first/ $first
/**
     * Gets a field name for a $group operation representing the value of the given expression when applied to the first member of
     * the group.
     *
     * @param fieldName the field name
     * @param expression the expression
     * @param <TExpression> the expression type
     * @return the field
     * @mongodb.driver.manual reference/operator/aggregation/first/ $first
     */
    public static <TExpression> BsonField first(final String fieldName, final TExpression expression) {
        return accumulator("$first", fieldName, expression);
    }

    
Gets a field name for a $group operation representing the value of the given expression when applied to the last member of
the group.

Params:
  • fieldName – the field name
  • expression – the expression
Type parameters:
Returns:the field
@mongodb.driver.manualreference/operator/aggregation/last/ $last
/**
     * Gets a field name for a $group operation representing the value of the given expression when applied to the last member of
     * the group.
     *
     * @param fieldName the field name
     * @param expression the expression
     * @param <TExpression> the expression type
     * @return the field
     * @mongodb.driver.manual reference/operator/aggregation/last/ $last
     */
    public static <TExpression> BsonField last(final String fieldName, final TExpression expression) {
        return accumulator("$last", fieldName, expression);
    }

    
Gets a field name for a $group operation representing the maximum of the values of the given expression when applied to all
members of the group.

Params:
  • fieldName – the field name
  • expression – the expression
Type parameters:
Returns:the field
@mongodb.driver.manualreference/operator/aggregation/max/ $max
/**
     * Gets a field name for a $group operation representing the maximum of the values of the given expression when applied to all
     * members of the group.
     *
     * @param fieldName the field name
     * @param expression the expression
     * @param <TExpression> the expression type
     * @return the field
     * @mongodb.driver.manual reference/operator/aggregation/max/ $max
     */
    public static <TExpression> BsonField max(final String fieldName, final TExpression expression) {
        return accumulator("$max", fieldName, expression);
    }

    
Gets a field name for a $group operation representing the minimum of the values of the given expression when applied to all
members of the group.

Params:
  • fieldName – the field name
  • expression – the expression
Type parameters:
Returns:the field
@mongodb.driver.manualreference/operator/aggregation/min/ $min
/**
     * Gets a field name for a $group operation representing the minimum of the values of the given expression when applied to all
     * members of the group.
     *
     * @param fieldName the field name
     * @param expression the expression
     * @param <TExpression> the expression type
     * @return the field
     * @mongodb.driver.manual reference/operator/aggregation/min/ $min
     */
    public static <TExpression> BsonField min(final String fieldName, final TExpression expression) {
        return accumulator("$min", fieldName, expression);
    }

    
Gets a field name for a $group operation representing an array of all values that results from applying an expression to each
document in a group of documents that share the same group by key.

Params:
  • fieldName – the field name
  • expression – the expression
Type parameters:
Returns:the field
@mongodb.driver.manualreference/operator/aggregation/push/ $push
/**
     * Gets a field name for a $group operation representing an array of all values that results from applying an expression to each
     * document in a group of documents that share the same group by key.
     *
     * @param fieldName the field name
     * @param expression the expression
     * @param <TExpression> the expression type
     * @return the field
     * @mongodb.driver.manual reference/operator/aggregation/push/ $push
     */
    public static <TExpression> BsonField push(final String fieldName, final TExpression expression) {
        return accumulator("$push", fieldName, expression);
    }

    
Gets a field name for a $group operation representing all unique values that results from applying the given expression to each
document in a group of documents that share the same group by key.

Params:
  • fieldName – the field name
  • expression – the expression
Type parameters:
Returns:the field
@mongodb.driver.manualreference/operator/aggregation/addToSet/ $addToSet
/**
     * Gets a field name for a $group operation representing all unique values that results from applying the given expression to each
     * document in a group of documents that share the same group by key.
     *
     * @param fieldName the field name
     * @param expression the expression
     * @param <TExpression> the expression type
     * @return the field
     * @mongodb.driver.manual reference/operator/aggregation/addToSet/ $addToSet
     */
    public static <TExpression> BsonField addToSet(final String fieldName, final TExpression expression) {
        return accumulator("$addToSet", fieldName, expression);
    }

    
Gets a field name for a $group operation representing the sample standard deviation of the values of the given expression
when applied to all members of the group.

Use if the values encompass the entire population of data you want to represent and do not wish to generalize about
a larger population.


Params:
  • fieldName – the field name
  • expression – the expression
Type parameters:
Returns:the field
@mongodb.driver.manualreference/operator/aggregation/stdDevPop/ $stdDevPop
@mongodb.server.release3.2
Since:3.2
/**
     * Gets a field name for a $group operation representing the sample standard deviation of the values of the given expression
     * when applied to all members of the group.
     *
     * <p>Use if the values encompass the entire population of data you want to represent and do not wish to generalize about
     * a larger population.</p>
     *
     * @param fieldName the field name
     * @param expression the expression
     * @param <TExpression> the expression type
     * @return the field
     * @mongodb.driver.manual reference/operator/aggregation/stdDevPop/ $stdDevPop
     * @mongodb.server.release 3.2
     * @since 3.2
     */
    public static <TExpression> BsonField stdDevPop(final String fieldName, final TExpression expression) {
        return accumulator("$stdDevPop", fieldName, expression);
    }

    
Gets a field name for a $group operation representing the sample standard deviation of the values of the given expression
when applied to all members of the group.

Use if the values encompass a sample of a population of data from which to generalize about the population.


Params:
  • fieldName – the field name
  • expression – the expression
Type parameters:
Returns:the field
@mongodb.driver.manualreference/operator/aggregation/stdDevSamp/ $stdDevSamp
@mongodb.server.release3.2
Since:3.2
/**
     * Gets a field name for a $group operation representing the sample standard deviation of the values of the given expression
     * when applied to all members of the group.
     *
     * <p>Use if the values encompass a sample of a population of data from which to generalize about the population.</p>
     *
     * @param fieldName the field name
     * @param expression the expression
     * @param <TExpression> the expression type
     * @return the field
     * @mongodb.driver.manual reference/operator/aggregation/stdDevSamp/ $stdDevSamp
     * @mongodb.server.release 3.2
     * @since 3.2
     */
    public static <TExpression> BsonField stdDevSamp(final String fieldName, final TExpression expression) {
        return accumulator("$stdDevSamp", fieldName, expression);
    }

    private static <TExpression> BsonField accumulator(final String name, final String fieldName, final TExpression expression) {
        return new BsonField(fieldName, new SimpleExpression<TExpression>(name, expression));
    }

    private Accumulators() {
    }
}