/*
* Copyright 2015 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
*
* 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.manual core/aggregation-pipeline/ Aggregation pipeline
* @mongodb.driver.manual 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.
*
* @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.
*
* @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.
*
* @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.
*
* @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.
*
* @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.
*
* @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.
*
* @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.
*
* @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.
*
* <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.
*
* <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() {
}
}