> For the complete documentation index, see [llms.txt](https://docs.mongoing.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.mongoing.com/aggregation/aggregation-reference/aggregation-commands-commparison.md).

# 聚合命令对比

在本页面

* [聚合命令比较表](#aggregation-commands-comparison-table)

> **\[success] 建议**
>
> 从4.4版开始，MongoDB添加[`$accumulator`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)和 [`$function`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)运算符。使用 [`$accumulator`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)和[`$function`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)， [`mapReduce`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)可以使用聚合运算符重写表达式。
>
> 即使是4.4版本之前，一些map-reduce表达式也可以使用改写[其他聚合管道运算符](/aggregation/aggregation-reference/aggregation-commands-commparison.md)，如[`$group`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)， [`$merge`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)等。

## 聚合命令比较表

以下表格简要概述了 MongoDB 聚合命令的特点。

|          |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                |                                                                                                                                                                                                                                  |
| -------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------ | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
|          | [Aggregate](/aggregation/aggregation-reference/aggregation-commands-commparison.md) / [db.collection.aggregate()](/aggregation/aggregation-reference/aggregation-commands-commparison.md)                                                                                                                                                                                                                                                                                                                                                                                                                                                                                      | [MapReduce](/aggregation/aggregation-reference/aggregation-commands-commparison.md) / [db.collection.mapReduce()](/aggregation/aggregation-reference/aggregation-commands-commparison.md)                                        |
| **描述**   | 旨在提高聚合任务的性能和可用性的具体目标。 使用“管道”方法，其中 objects 在通过一系列管道操作符(如[$group](/aggregation/aggregation-reference/aggregation-commands-commparison.md)，[$match](/aggregation/aggregation-reference/aggregation-commands-commparison.md)和[$sort](/aggregation/aggregation-reference/aggregation-commands-commparison.md))时进行转换。 有关管道运算符的更多信息，请参见[聚合管道操作符](https://github.com/mongodb-china/MongoDB-CN-Manual/tree/8490376c81d56eff95abbaddc6ee414b1e1c9705/docs/docs/Reference/Operators/Aggregation-Pipline-Operators.md)。                                                                                                                                                                    | 实现 Map-Reduce 聚合以处理大型数据集。                                                                                                                                                                                                        |
| **主要特点** | 可以根据需要重复管道操作符。 管道运算符不需要为每个输入文档生成一个输出文档。 还可以生成新文档或过滤掉文档。 通过在版本4.2中添加`$merge`，可以创建按需的物化视图，在该视图中可以逐步运行管道来更新输出集合的内容。`$merge`可以将结果(插入新文档、合并文档、替换文档、保留现有文档、使操作失败、使用自定义更新管道处理文档)合并到现有集合中。                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             | 除了分组操作之外，还可以执行复杂的聚合任务以及对不断增长的数据集执行增量聚合。 见[Map-Reduce 例子](/aggregation/aggregation-reference/aggregation-commands-commparison.md)和[执行增量 Map-Reduce](/aggregation/aggregation-reference/aggregation-commands-commparison.md)。      |
| **灵活性**  | 从4.4版开始，可以使用[`$accumulator`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)和[`$function`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)定义自定义聚合表达式。 在以前的版本中，只能使用聚合管道支持的运算符和表达式。 但是，可以使用[`$project`](/aggregation/aggregation-reference/aggregation-commands-commparison.md) 管道运算符添加计算字段，创建新的虚拟子对象以及将子字段提取到结果的顶层。 有关更多信息，请参阅[`$project`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)以及[聚合管道操作符](/aggregation/aggregation-reference/aggregation-commands-commparison.md)，以了解有关所有可用管道操作符的更多信息。                                                                                                      | 自定义`map`，`reduce`和`finalize JavaScript` 函数为聚合逻辑提供了灵活性。 有关功能的详细信息和限制，请参阅[MapReduce](/aggregation/aggregation-reference/aggregation-commands-commparison.md)。                                                                      |
| **输出结果** | 以游标的形式返回结果。如果管道包含[`$out`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)阶段或[`$merge`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)阶段，则游标为空。 使用[`$out`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)，您可以完全替换现有的输出集合或输出到新的集合。详情见[`$out`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)。 使用[`$merge`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)，您可以输出到新的或现有的集合。对于现有的cllections，可以指定如何将结果合并到输出集合中(插入新文档、合并文档、替换文档、保留现有文档、使操作失败、使用自定义更新管道处理文档)。有关详细信息，请参见[`$merge`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)。 | 返回各种选项的结果(内联，新集合，合并，替换，减少)。有关输出选项的详细信息，请参阅[MapReduce](/aggregation/aggregation-reference/aggregation-commands-commparison.md)。                                                                                                   |
| **分片**   | 支持非分片和分片输入集合。 [`$merge`](/aggregation/aggregation-reference/aggregation-commands-commparison.md)可以输出到非分片或分片集合。                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 | 支持非分片和分片输入集合。                                                                                                                                                                                                                    |
| **更多信息** | [聚合管道](https://github.com/mongodb-china/MongoDB-CN-Manual/tree/8490376c81d56eff95abbaddc6ee414b1e1c9705/docs/Aggregation/Aggregation-Pipline.md) [db.collection.aggregate()](/aggregation/aggregation-reference/aggregation-commands-commparison.md) [aggregate](/aggregation/aggregation-reference/aggregation-commands-commparison.md)                                                                                                                                                                                                                                                                                                                                       | [Map-Reduce](/aggregation/map-reduce.md) [db.collection.mapReduce()](/aggregation/aggregation-reference/aggregation-commands-commparison.md) [mapReduce](/aggregation/aggregation-reference/aggregation-commands-commparison.md) |

也可以看看

* [Map-Reduce to Aggregate](/aggregation/aggregation-reference/aggregation-commands-commparison.md)

译者：李冠飞

校对：李冠飞


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.mongoing.com/aggregation/aggregation-reference/aggregation-commands-commparison.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.