Run a Database Command运行数据库命令

Overview概述

In this guide, you can learn how to run a database command with the Node.js driver. You can use database commands to perform a variety of administrative and diagnostic tasks, such as fetching server statistics, initializing a replica set, or running an aggregation pipeline.在本指南中，您可以学习如何使用Node.js驱动程序运行数据库命令。您可以使用数据库命令执行各种管理和诊断任务，例如获取服务器统计信息、初始化副本集或运行聚合管道。

Execute a Command执行命令

To run a database command, you must specify the command and any relevant parameters in a document, then pass this document to a command execution method. The Node.js driver provides the following methods to run database commands:要运行数据库命令，您必须在文档中指定命令和任何相关参数，然后将此文档传递给命令执行方法。Node.js驱动程序提供以下方法来运行数据库命令：

• command(), which returns the command response as a Document type. You can use this method with any database command.，它将命令响应作为Document类型返回。您可以将此方法与任何数据库命令一起使用。
• runCursorCommand(), which returns the command response as an iterable RunCommandCursor type. ，它将命令响应作为可迭代的RunCommandCursor类型返回。You can use this method only if your database command returns multiple result documents.只有当数据库命令返回多个结果文档时，才能使用此方法。

The following code shows how you can use the command() method to run the hello command, which returns information about the current member's role in the replica set, on a database:以下代码显示了如何使用command()方法在数据库上运行hello命令，该命令返回有关副本集中当前成员角色的信息：

const result = await myDB.command({ hello: 1 });

For a full list of database commands and corresponding parameters, see the Additional Information section.有关数据库命令和相应参数的完整列表，请参阅附加信息部分。

Command Options命令选项

You can specify optional command behavior for the command() and runCursorCommand() methods.您可以为command()和runCursorCommand()方法指定可选的命令行为。

The command() method accepts a RunCommandOptions object. To learn more about the RunCommandOptions type, see the API documentation.command()方法接受RunCommandOptions对象。要了解有关RunCommandOptions类型的更多信息，请参阅API文档。

The runCursorCommand() method accepts a RunCursorCommandOptions object. To learn more about the RunCursorCommandOptions type, see the API documentation.runCursorCommand()方法接受RunCursorCommandOptions对象。要了解有关RunCursorCommandOptions类型的更多信息，请参阅API文档。

Starting in version 6.0 of the Node.js driver, you can pass only the following options to the command() method:从Node.js驱动程序的6.0版本开始，您只能将以下选项传递给command()方法：

• comment
• enableUtf8Validation
• raw
• readPreference
• session

You can set more options in the document that you pass to the command() method. To learn more about a command and the options that it accepts, locate the command and follow the link on the Database Commands section of the Server manual.您可以在传递给command()方法的文档中设置更多选项。要了解有关命令及其接受的选项的更多信息，请找到该命令并按照服务器手册“数据库命令”部分上的链接进行操作。

The following code shows how to specify a grantRolesToUser command that executes with a majority write concern:以下代码显示了如何指定以majority写入关注执行的grantRolesToUser命令：

const commandDoc = {
    grantRolesToUser: "user011",
    roles: [ "readWrite" ],
    writeConcern: { w: "majority" }
};
const result = await myDB.command(commandDoc);

const commandOptions = { readPreference: "nearest" };
const result = await myDB.command(commandDoc, commandOptions);

Response响应

Each method returns a Document object or a cursor that contains the response from the database after the command has been executed. Each database command performs a different function, so the response content can vary across commands. However, every response contains documents with the following fields:每个方法都返回一个Document对象或游标，其中包含执行命令后数据库的响应。每个数据库命令执行不同的功能，因此响应内容可能因命令而异。但是，每个响应都包含具有以下字段的文档：

Example示例

The following code shows how you can use the runCursorCommand() method to run the checkMetadataConsistency command on the testDB database and iterate through the results:以下代码显示了如何使用runCursorCommand()方法在testDB数据库上运行checkMetadataConsistency命令并迭代结果：

// Connect to the "testDB" database连接到“testDB”数据库
const db = client.db("testDB");

// Run a cursor command to check metadata consistency within the database
const cursor = await db.runCursorCommand({
    checkMetadataConsistency: 1,
});
// Iterate through the cursor's results and print the contents
for await (const doc of cursor) {
  console.log(doc);
}

{
  type: ...,
  description: ...,
  details: {
    namespace: ...,
    info: ...
  }
}
{
  type: ...,
  description: ...,
  details: {
    namespace: ...,
    collectionUUID: ...,
    maxKeyObj: ...,
    ...
  }
}

Run Command Example: Full File运行命令示例：完整文件

In the following sample code, we send the dbStats command to request statistics from the sample_mflix database:在以下示例代码中，我们发送dbStats命令以从sample_mflix数据库请求统计信息：

/* Run a database command运行数据库命令 */

import { MongoClient } from "mongodb";

// Replace the uri string with your MongoDB deployment's connection string将uri字符串替换为MongoDB部署的连接字符串
const uri = "<connection string uri>";

const client = new MongoClient(uri);

async function run() {
  try {
    // Get the "sample_mflix" database获取“sample_mflix”数据库
    const db = client.db("sample_mflix");

    // Find and print the storage statistics for the "sample_mflix" database using the 'dbStats' command使用“dbStats”命令查找并打印“sample_mflix”数据库的存储统计信息
    const result = await db.command({
      dbStats: 1,
    });
    console.log(result);
  } finally {
    // Close the database connection on completion or error完成或出错时关闭数据库连接
    await client.close();
  }
}
run().catch(console.dir);

Running the preceding command results in the following output:运行上述命令会得到以下输出：

{
  db: 'sample_mflix',
  collections: 6,
  views: 0,
  objects: 75620,
  ..

Additional Information附加信息

For more information about the concepts in this guide, see the following documentation:有关本指南中概念的更多信息，请参阅以下文档：

• db.runCommand()
• Database Commands
• hello Command
• find Command

To learn how to retrieve data from a cursor, see the Access Data From a Cursor fundamentals page.要了解如何从游标检索数据，请参阅从游标访问数据基本原理页面。