com.mongodb.client.model

枚举 MapReduceAction

java.lang.Object

java.lang.Enum<MapReduceAction>

com.mongodb.client.model.MapReduceAction

所有已实现的接口:

java.io.Serializable, java.lang.Comparable<MapReduceAction>

public enum MapReduceAction
extends java.lang.Enum<MapReduceAction>

The map reduce to collection actions.

These actions are only available when passing out a collection that already exists. This option is not available on secondary members of replica sets. The Enum values dictate what to do with the output collection if it already exists when the map reduce is run.

从以下版本开始:

3.0

MongoDB documentation

mapReduce Command

mapReduce Overview

枚举常量概要

枚举常量

枚举常量和说明
MERGE Merge the new result with the existing result if the output collection already exists.
REDUCE Merge the new result with the existing result if the output collection already exists.
REPLACE Replace the contents of the collectionName if the collection with the collectionName exists.

方法概要

限定符和类型	方法和说明
java.lang.String	getValue()
static MapReduceAction	valueOf(java.lang.String name) 返回带有指定名称的该类型的枚举常量。
static MapReduceAction[]	values() 按照声明该枚举类型的常量的顺序, 返回 包含这些常量的数组。

从类继承的方法 java.lang.Enum

clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf

从类继承的方法 java.lang.Object

getClass, notify, notifyAll, wait, wait, wait

枚举常量详细资料

REPLACE

public static final MapReduceAction REPLACE

Replace the contents of the collectionName if the collection with the collectionName exists.

MERGE

public static final MapReduceAction MERGE

Merge the new result with the existing result if the output collection already exists. If an existing document has the same key as the new result, overwrite that existing document.

REDUCE

public static final MapReduceAction REDUCE

Merge the new result with the existing result if the output collection already exists. If an existing document has the same key as the new result, apply the reduce function to both the new and the existing documents and overwrite the existing document with the result.

方法详细资料

values

public static MapReduceAction[] values()

按照声明该枚举类型的常量的顺序, 返回 包含这些常量的数组。该方法可用于迭代 常量, 如下所示:

for (MapReduceAction c : MapReduceAction.values())
    System.out.println(c);

返回:

按照声明该枚举类型的常量的顺序返回的包含这些常量的数组

valueOf

public static MapReduceAction valueOf(java.lang.String name)

返回带有指定名称的该类型的枚举常量。 字符串必须与用于声明该类型的枚举常量的 标识符完全匹配。(不允许有多余 的空格字符。)

参数:

name - 要返回的枚举常量的名称。

返回:

返回带有指定名称的枚举常量

抛出:

java.lang.IllegalArgumentException - 如果该枚举类型没有带有指定名称的常量

java.lang.NullPointerException - 如果参数为空值

getValue

public java.lang.String getValue()

返回:

the String representation of this Action that the MongoDB server understands