Filter Data筛选数据

Create the Template App创建模板应用程序

Before you begin following this aggregation tutorial, you must set up a new C app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习此聚合教程之前，您必须设置一个新的C应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the driver, create a file called agg-tutorial.c. Paste the following code in this file to create an app template for the aggregation tutorials.安装驱动程序后，创建一个名为agg-tutorial.c的文件。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

#include <stdio.h>
#include <bson/bson.h>
#include <mongoc/mongoc.h>

int main(void)
{
    mongoc_init();

    // Replace the placeholder with your connection string.
    char *uri = "<connection string>";
    mongoc_client_t* client = mongoc_client_new(uri);

    // Get a reference to relevant collections.
    // ... mongoc_collection_t *some_coll = mongoc_client_get_collection(client, "agg_tutorials_db", "some_coll");
    // ... mongoc_collection_t *another_coll = mongoc_client_get_collection(client, "agg_tutorials_db", "another_coll");

    // Delete any existing documents in collections if needed.
    // ... {
    // ...     bson_t *filter = bson_new();
    // ...     bson_error_t error;
    // ...     if (!mongoc_collection_delete_many(some_coll, filter, NULL, NULL, &error))
    // ...     {
    // ...         fprintf(stderr, "Delete error: %s\n", error.message);
    // ...     }
    // ...     bson_destroy(filter);
    // ... }

    // Insert sample data into the collection or collections.
    // ... {
    // ...     size_t num_docs = ...;
    // ...     bson_t *docs[num_docs];
    // ...
    // ...     docs[0] = ...;
    // ...
    // ...     bson_error_t error;
    // ...     if (!mongoc_collection_insert_many(some_coll, (const bson_t **)docs, num_docs, NULL, NULL, &error))
    // ...     {
    // ...         fprintf(stderr, "Insert error: %s\n", error.message);
    // ...     }
    // ...
    // ...     for (int i = 0; i < num_docs; i++)
    // ...     {
    // ...         bson_destroy(docs[i]);
    // ...     }
    // ... }

    {
        const bson_t *doc;

        // Add code to create pipeline stages.
        bson_t *pipeline = BCON_NEW("pipeline", "[",
        // ... Add pipeline stages here.
        "]");

        // Run the aggregation.
        // ... mongoc_cursor_t *results = mongoc_collection_aggregate(some_coll, MONGOC_QUERY_NONE, pipeline, NULL, NULL);

        bson_destroy(pipeline);

        // Print the aggregation results.
        while (mongoc_cursor_next(results, &doc))
        {
            char *str = bson_as_canonical_extended_json(doc, NULL);
            printf("%s\n", str);
            bson_free(str);
        }
        bson_error_t error;
        if (mongoc_cursor_error(results, &error))
        {
            fprintf(stderr, "Aggregation error: %s\n", error.message);
        }

        mongoc_cursor_destroy(results);
    }

    // Clean up resources.
    // ... mongoc_collection_destroy(some_coll);
    mongoc_client_destroy(client);
    mongoc_cleanup();

    return EXIT_SUCCESS;
}

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

char *uri = "mongodb+srv://mongodb-example:27017";

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

mongoc_collection_t *persons = mongoc_client_get_collection(client, "agg_tutorials_db", "persons");

{
    bson_t *filter = bson_new();
    bson_error_t error;
    if (!mongoc_collection_delete_many(persons, filter, NULL, NULL, &error))
    {
        fprintf(stderr, "Delete error: %s\n", error.message);
    }
    bson_destroy(filter);
}

{
    size_t num_docs = 6;
    bson_t *docs[num_docs];

    docs[0] = BCON_NEW(
        "person_id", "6392529400",
        "firstname", "Elise",
        "lastname", "Smith",
        "dateofbirth", BCON_DATE_TIME(653616727000UL), // 1972-01-13T09:32:07Z
        "vocation", "ENGINEER",
        "address", "{",
        "number", BCON_INT32(5625),
        "street", "Tipa Circle",
        "city", "Wojzinmoj",
        "}");

    docs[1] = BCON_NEW(
        "person_id", "1723338115",
        "firstname", "Olive",
        "lastname", "Ranieri",
        "dateofbirth", BCON_DATE_TIME(485113500000UL), // 1985-05-12T23:14:30Z
        "gender", "FEMALE",
        "vocation", "ENGINEER",
        "address", "{",
        "number", BCON_INT32(9303),
        "street", "Mele Circle",
        "city", "Tobihbo",
        "}");

    docs[2] = BCON_NEW(
        "person_id", "8732762874",
        "firstname", "Toni",
        "lastname", "Jones",
        "dateofbirth", BCON_DATE_TIME(690559710000UL), // 1991-11-23T16:53:56Z
        "vocation", "POLITICIAN",
        "address", "{",
        "number", BCON_INT32(1),
        "street", "High Street",
        "city", "Upper Abbeywoodington",
        "}");

    docs[3] = BCON_NEW(
        "person_id", "7363629563",
        "firstname", "Bert",
        "lastname", "Gooding",
        "dateofbirth", BCON_DATE_TIME(449595112000UL), // 1941-04-07T22:11:52Z
        "vocation", "FLORIST",
        "address", "{",
        "number", BCON_INT32(13),
        "street", "Upper Bold Road",
        "city", "Redringtonville",
        "}");

    docs[4] = BCON_NEW(
        "person_id", "1029648329",
        "firstname", "Sophie",
        "lastname", "Celements",
        "dateofbirth", BCON_DATE_TIME(316265745000UL), // 1959-07-06T17:35:45Z
        "vocation", "ENGINEER",
        "address", "{",
        "number", BCON_INT32(5),
        "street", "Innings Close",
        "city", "Basilbridge",
        "}");

    docs[5] = BCON_NEW(
        "person_id", "7363626383",
        "firstname", "Carl",
        "lastname", "Simmons",
        "dateofbirth", BCON_DATE_TIME(915250045000UL), // 1998-12-26T13:13:55Z
        "vocation", "ENGINEER",
        "address", "{",
        "number", BCON_INT32(187),
        "street", "Hillside Road",
        "city", "Kenningford",
        "}");

    bson_error_t error;
    if (!mongoc_collection_insert_many(persons, (const bson_t **)docs, num_docs, NULL, NULL, &error))
    {
        fprintf(stderr, "Insert error: %s\n", error.message);
    }

    for (int i = 0; i < num_docs; i++)
    {
        bson_destroy(docs[i]);
    }
}

Create the Template App创建模板应用程序

Before you begin following an aggregation tutorial, you must set up a new C++ app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习聚合教程之前，您必须设置一个新的C++应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the driver, create a file called agg-tutorial.cpp. Paste the following code in this file to create an app template for the aggregation tutorials.安装驱动程序后，创建一个名为agg-tutorial.cpp的文件。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

#include <iostream>
#include <bsoncxx/builder/basic/document.hpp>
#include <bsoncxx/builder/basic/kvp.hpp>
#include <bsoncxx/json.hpp>
#include <mongocxx/client.hpp>
#include <mongocxx/instance.hpp>
#include <mongocxx/pipeline.hpp>
#include <mongocxx/uri.hpp>
#include <chrono>

using bsoncxx::builder::basic::kvp;
using bsoncxx::builder::basic::make_document;
using bsoncxx::builder::basic::make_array;

int main() {
   mongocxx::instance instance;

   // Replace the placeholder with your connection string.
   mongocxx::uri uri("<connection string>");
   mongocxx::client client(uri);

   auto db = client["agg_tutorials_db"];
   // Delete existing data in the database, if necessary.
   db.drop();

   // Get a reference to relevant collections.
   // ... auto some_coll = db["..."];
   // ... auto another_coll = db["..."];

   // Insert sample data into the collection or collections.
   // ... some_coll.insert_many(docs);

   // Create an empty pipelne.
   mongocxx::pipeline pipeline;

   // Add code to create pipeline stages.
   // pipeline.match(make_document(...));

   // Run the aggregation and print the results.
   auto cursor = orders.aggregate(pipeline);
   for (auto&& doc : cursor) {
      std::cout << bsoncxx::to_json(doc, bsoncxx::ExtendedJsonMode::k_relaxed) << std::endl;
   }
}

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

mongocxx::uri uri{"mongodb+srv://mongodb-example:27017"};

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

auto persons = db["persons"];

std::vector<bsoncxx::document::value> docs = {
    bsoncxx::from_json(R"({
        "person_id": "6392529400",
        "firstname": "Elise",
        "lastname": "Smith",
        "dateofbirth": {"$date": 620947927},
        "vocation": "ENGINEER",
        "address": {
            "number": 5625,
            "street": "Tipa Circle",
            "city": "Wojzinmoj"
        }
    })"),
    bsoncxx::from_json(R"({
        "person_id": "1723338115",
        "firstname": "Olive",
        "lastname": "Ranieri",
        "dateofbirth": {"$date": 485529270000},
        "gender": "FEMALE",
        "vocation": "ENGINEER",
        "address": {
            "number": 9303,
            "street": "Mele Circle",
            "city": "Tobihbo"
        }
    })"),
    bsoncxx::from_json(R"({
        "person_id": "8732762874",
        "firstname": "Toni",
        "lastname": "Jones",
        "dateofbirth": {"$date": 690978836000},
        "vocation": "POLITICIAN",
        "address": {
            "number": 1,
            "street": "High Street",
            "city": "Upper Abbeywoodington"
        }
    })"),
    bsoncxx::from_json(R"({
        "person_id": "7363629563",
        "firstname": "Bert",
        "lastname": "Gooding",
        "dateofbirth": {"$date": -88368048000},
        "vocation": "FLORIST",
        "address": {
            "number": 13,
            "street": "Upper Bold Road",
            "city": "Redringtonville"
        }
    })"),
    bsoncxx::from_json(R"({
        "person_id": "1029648329",
        "firstname": "Sophie",
        "lastname": "Celements",
        "dateofbirth": {"$date": -31561935000},
        "vocation": "ENGINEER",
        "address": {
            "number": 5,
            "street": "Innings Close",
            "city": "Basilbridge"
        }
    })"),
    bsoncxx::from_json(R"({
        "person_id": "7363626383",
        "firstname": "Carl",
        "lastname": "Simmons",
        "dateofbirth": {"$date": 915148835000},
        "vocation": "ENGINEER",
        "address": {
            "number": 187,
            "street": "Hillside Road",
            "city": "Kenningford"
        }
    })")
};

auto result = persons.insert_many(docs); // Might throw an exception

Create the Template App创建模板应用程序

Before you begin following this aggregation tutorial, you must set up a new C#/.NET app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习此聚合教程之前，您必须设置一个新的C#/NET应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the driver, paste the following code into your Program.cs file to create an app template for the aggregation tutorials.安装驱动程序后，将以下代码粘贴到Program.cs文件中，为聚合教程创建应用程序模板。

using MongoDB.Bson;
using MongoDB.Bson.Serialization.Attributes;
using MongoDB.Driver;

// Define data model classes.
// ... public class MyClass { ... }

// Replace the placeholder with your connection string.
var uri = "<connection string>";
var client = new MongoClient(uri);
var aggDB = client.GetDatabase("agg_tutorials_db");

// Get a reference to relevant collections.
// ... var someColl = aggDB.GetCollection<MyClass>("someColl");
// ... var anotherColl = aggDB.GetCollection<MyClass>("anotherColl");

// Delete any existing documents in collections if needed.
// ... someColl.DeleteMany(Builders<MyClass>.Filter.Empty);

// Insert sample data into the collection or collections.
// ... someColl.InsertMany(new List<MyClass> { ... });

// Add code to chain pipeline stages to the Aggregate() method.
// ... var results = someColl.Aggregate().Match(...);

// Print the aggregation results.
foreach (var result in results.ToList())
{
    Console.WriteLine(result);
}

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

var uri = "mongodb+srv://mongodb-example:27017";

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

First, create C# classes to model the data in the persons collection:首先，创建C#类来对persons集合中的数据进行建模：

public class Person
{
    [BsonId]
    public ObjectId Id { get; set; }
    public string PersonId { get; set; } = "";
    public string FirstName { get; set; } = "";
    public string LastName { get; set; } = "";
    public DateTime DateOfBirth { get; set; }
    [BsonIgnoreIfNull]
    public string? Gender { get; set; }
    public string Vocation { get; set; } = "";
    public Address? Address { get; set; }
}

public class Address
{
    public int Number { get; set; }
    public string Street { get; set; } = "";
    public string City { get; set; } = "";
}

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

var persons = aggDB.GetCollection<Person>("persons");

persons.InsertMany(new List<Person>
{
    new Person
    {
        PersonId = "6392529400",
        FirstName = "Elise",
        LastName = "Smith",
        DateOfBirth = DateTime.Parse("1972-01-13T09:32:07Z"),
        Vocation = "ENGINEER",
        Address = new Address
        {
            Number = 5625,
            Street = "Tipa Circle",
            City = "Wojzinmoj"
        }
    },
    new Person
    {
        PersonId = "1723338115",
        FirstName = "Olive",
        LastName = "Ranieri",
        DateOfBirth = DateTime.Parse("1985-05-12T23:14:30Z"),
        Gender = "FEMALE",
        Vocation = "ENGINEER",
        Address = new Address
        {
            Number = 9303,
            Street = "Mele Circle",
            City = "Tobihbo"
        }
    },
    new Person
    {
        PersonId = "8732762874",
        FirstName = "Toni",
        LastName = "Jones",
        DateOfBirth = DateTime.Parse("1991-11-23T16:53:56Z"),
        Vocation = "POLITICIAN",
        Address = new Address
        {
            Number = 1,
            Street = "High Street",
            City = "Upper Abbeywoodington"
        }
    },
    new Person
    {
        PersonId = "7363629563",
        FirstName = "Bert",
        LastName = "Gooding",
        DateOfBirth = DateTime.Parse("1941-04-07T22:11:52Z"),
        Vocation = "FLORIST",
        Address = new Address
        {
            Number = 13,
            Street = "Upper Bold Road",
            City = "Redringtonville"
        }
    },
    new Person
    {
        PersonId = "1029648329",
        FirstName = "Sophie",
        LastName = "Celements",
        DateOfBirth = DateTime.Parse("1959-07-06T17:35:45Z"),
        Vocation = "ENGINEER",
        Address = new Address
        {
            Number = 5,
            Street = "Innings Close",
            City = "Basilbridge"
        }
    },
    new Person
    {
        PersonId = "7363626383",
        FirstName = "Carl",
        LastName = "Simmons",
        DateOfBirth = DateTime.Parse("1998-12-26T13:13:55Z"),
        Vocation = "ENGINEER",
        Address = new Address
        {
            Number = 187,
            Street = "Hillside Road",
            City = "Kenningford"
        }
    }
});

Create the Template App创建模板应用程序

Before you begin following this aggregation tutorial, you must set up a new Go app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习此聚合教程之前，您必须设置一个新的Go应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the driver, create a file called agg_tutorial.go. Paste the following code in this file to create an app template for the aggregation tutorials.安装驱动程序后，创建一个名为agg_tutorial.go的文件。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

package main

import (
	"context"
	"fmt"
	"log"

	"go.mongodb.org/mongo-driver/v2/bson"
	"go.mongodb.org/mongo-driver/v2/mongo"
	"go.mongodb.org/mongo-driver/v2/mongo/options"
)

// Define structs.
// type MyStruct struct { ... }

func main() {
	ctx := context.Background()
	// Replace the placeholder with your connection string.
	const uri = "<connection string>"

	client, err := mongo.Connect(options.Client().ApplyURI(uri))
	if err != nil {
		log.Fatal(err)
	}

	defer func() {
		if err = client.Disconnect(ctx); err != nil {
			log.Fatal(err)
		}
	}()

	aggDB := client.Database("agg_tutorials_db")

	// Get a reference to relevant collections.
	// ... someColl := aggDB.Collection("...")
	// ... anotherColl := aggDB.Collection("...")

	// Delete any existing documents in collections if needed.
	// ... someColl.DeleteMany(cxt, bson.D{})

	// Insert sample data into the collection or collections.
	// ... _, err = someColl.InsertMany(...)

	// Add code to create pipeline stages.
	// ... myStage := bson.D{{...}}

	// Create a pipeline that includes the stages.
	// ... pipeline := mongo.Pipeline{...}

	// Run the aggregation.
	// ... cursor, err := someColl.Aggregate(ctx, pipeline)

	if err != nil {
		log.Fatal(err)
	}

	defer func() {
		if err := cursor.Close(ctx); err != nil {
			log.Fatalf("failed to close cursor: %v", err)
		}
	}()

	// Decode the aggregation results.
	var results []bson.D
	if err = cursor.All(ctx, &results); err != nil {
		log.Fatalf("failed to decode results: %v", err)
	}

	// Print the aggregation results.
	for _, result := range results {
		res, _ := bson.MarshalExtJSON(result, false, false)
		fmt.Println(string(res))
	}
}

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

const uri = "mongodb+srv://mongodb-example:27017";

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

First, create Go structs to model the data in the persons collection:首先，创建Go结构体来对persons集合中的数据进行建模：

type Person struct {
	PersonID    string        `bson:"person_id"`
	Firstname   string        `bson:"firstname"`
	Lastname    string        `bson:"lastname"`
	Gender      string        `bson:"gender,omitempty"`
	DateOfBirth bson.DateTime `bson:"dateofbirth"`
	Vocation    string        `bson:"vocation"`
	Address     Address       `bson:"address"`
}

type Address struct {
	Number int
	Street string
	City   string
}

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

persons := aggDB.Collection("persons")

_, err = persons.InsertMany(ctx, []interface{}{
	Person{
		PersonID:    "6392529400",
		Firstname:   "Elise",
		Lastname:    "Smith",
		DateOfBirth: bson.NewDateTimeFromTime(time.Date(1972, 1, 13, 9, 32, 7, 0, time.UTC)),
		Vocation:    "ENGINEER",
		Address:     Address{Number: 5625, Street: "Tipa Circle", City: "Wojzinmoj"},
	},
	Person{
		PersonID:    "1723338115",
		Firstname:   "Olive",
		Lastname:    "Ranieri",
		Gender:      "FEMALE",
		DateOfBirth: bson.NewDateTimeFromTime(time.Date(1985, 5, 12, 23, 14, 30, 0, time.UTC)),
		Vocation:    "ENGINEER",
		Address:     Address{Number: 9303, Street: "Mele Circle", City: "Tobihbo"},
	},
	Person{
		PersonID:    "8732762874",
		Firstname:   "Toni",
		Lastname:    "Jones",
		DateOfBirth: bson.NewDateTimeFromTime(time.Date(1991, 11, 23, 16, 53, 56, 0, time.UTC)),
		Vocation:    "POLITICIAN",
		Address:     Address{Number: 1, Street: "High Street", City: "Upper Abbeywoodington"},
	},
	Person{
		PersonID:    "7363629563",
		Firstname:   "Bert",
		Lastname:    "Gooding",
		DateOfBirth: bson.NewDateTimeFromTime(time.Date(1941, 4, 7, 22, 11, 52, 0, time.UTC)),
		Vocation:    "FLORIST",
		Address:     Address{Number: 13, Street: "Upper Bold Road", City: "Redringtonville"},
	},
	Person{
		PersonID:    "1029648329",
		Firstname:   "Sophie",
		Lastname:    "Celements",
		DateOfBirth: bson.NewDateTimeFromTime(time.Date(1959, 7, 6, 17, 35, 45, 0, time.UTC)),
		Vocation:    "ENGINEER",
		Address:     Address{Number: 5, Street: "Innings Close", City: "Basilbridge"},
	},
	Person{
		PersonID:    "7363626383",
		Firstname:   "Carl",
		Lastname:    "Simmons",
		DateOfBirth: bson.NewDateTimeFromTime(time.Date(1998, 12, 26, 13, 13, 55, 0, time.UTC)),
		Vocation:    "ENGINEER",
		Address:     Address{Number: 187, Street: "Hillside Road", City: "Kenningford"},
	},
})
if err != nil {
	log.Fatal(err)
}

Create the Template App创建模板应用程序

Before you begin following an aggregation tutorial, you must set up a new Java app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习聚合教程之前，您必须设置一个新的Java应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the driver, create a file called AggTutorial.java. Paste the following code in this file to create an app template for the aggregation tutorials.安装驱动程序后，创建一个名为AggTutorial.java的文件。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

package org.example;

// Modify imports for each tutorial as needed.
import com.mongodb.client.*;
import com.mongodb.client.model.Accumulators;
import com.mongodb.client.model.Aggregates;
import com.mongodb.client.model.Field;
import com.mongodb.client.model.Filters;
import com.mongodb.client.model.Sorts;
import com.mongodb.client.model.Variable;
import org.bson.Document;
import org.bson.conversions.Bson;

import java.time.LocalDateTime;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class AggTutorial {
    public static void main(String[] args) {
        // Replace the placeholder with your connection string.
        String uri = "<connection string>";

        try (MongoClient mongoClient = MongoClients.create(uri)) {
            MongoDatabase aggDB = mongoClient.getDatabase("agg_tutorials_db");

            // Get a reference to relevant collections.
            // ... MongoCollection<Document> someColl = ...
            // ... MongoCollection<Document> anotherColl = ...

            // Insert sample data into the collection or collections.
            // ... someColl.insertMany(...);

            // Create an empty pipeline array.
            List<Bson> pipeline = new ArrayList<>();

            // Add code to create pipeline stages.
            // ... pipeline.add(...);

            // Run the aggregation.
            // ... AggregateIterable<Document> aggregationResult =
            // someColl.aggregate(pipeline);

            // Print the aggregation results.
            for (Document document : aggregationResult) {
                System.out.println(document.toJson());
            }
        }
    }
}

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

String uri = "mongodb+srv://mongodb-example:27017";

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

MongoDatabase aggDB = mongoClient.getDatabase("agg_tutorials_db");
MongoCollection<Document> persons = aggDB.getCollection("persons");

persons.insertMany(
        Arrays.asList(
                new Document("person_id", "6392529400")
                        .append("firstname", "Elise")
                        .append("lastname", "Smith")
                        .append("dateofbirth", LocalDateTime.parse("1972-01-13T09:32:07"))
                        .append("vocation", "ENGINEER")
                        .append("address", new Document("number", 5625)
                                .append("street", "Tipa Circle")
                                .append("city", "Wojzinmoj")),
                new Document("person_id", "1723338115")
                        .append("firstname", "Olive")
                        .append("lastname", "Ranieri")
                        .append("dateofbirth", LocalDateTime.parse("1985-05-12T23:14:30"))
                        .append("gender", "FEMALE")
                        .append("vocation", "ENGINEER")
                        .append("address", new Document("number", 9303)
                                .append("street", "Mele Circle")
                                .append("city", "Tobihbo")),
                new Document("person_id", "8732762874")
                        .append("firstname", "Toni")
                        .append("lastname", "Jones")
                        .append("dateofbirth", LocalDateTime.parse("1991-11-23T16:53:56"))
                        .append("vocation", "POLITICIAN")
                        .append("address", new Document("number", 1)
                                .append("street", "High Street")
                                .append("city", "Upper Abbeywoodington")),
                new Document("person_id", "7363629563")
                        .append("firstname", "Bert")
                        .append("lastname", "Gooding")
                        .append("dateofbirth", LocalDateTime.parse("1941-04-07T22:11:52"))
                        .append("vocation", "FLORIST")
                        .append("address", new Document("number", 13)
                                .append("street", "Upper Bold Road")
                                .append("city", "Redringtonville")),
                new Document("person_id", "1029648329")
                        .append("firstname", "Sophie")
                        .append("lastname", "Celements")
                        .append("dateofbirth", LocalDateTime.parse("1959-07-06T17:35:45"))
                        .append("vocation", "ENGINEER")
                        .append("address", new Document("number", 5)
                                .append("street", "Innings Close")
                                .append("city", "Basilbridge")),
                new Document("person_id", "7363626383")
                        .append("firstname", "Carl")
                        .append("lastname", "Simmons")
                        .append("dateofbirth", LocalDateTime.parse("1998-12-26T13:13:55"))
                        .append("vocation", "ENGINEER")
                        .append("address", new Document("number", 187)
                                .append("street", "Hillside Road")
                                .append("city", "Kenningford"))
        )
);

Create the Template App创建模板应用程序

Before you begin following an aggregation tutorial, you must set up a new Kotlin app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习聚合教程之前，您必须设置一个新的Kotlin应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

In addition to the driver, you must also add the following dependencies to your build.gradle.kts file and reload your project:除了驱动程序，您还必须将以下依赖项添加到build.gradle.kts文件中并重新加载项目：

dependencies {
    // Implements Kotlin serialization
    implementation("org.jetbrains.kotlinx:kotlinx-serialization-core:1.5.1")
    // Implements Kotlin date and time handling
    implementation("org.jetbrains.kotlinx:kotlinx-datetime:0.6.1")
}

After you install the driver, create a file called AggTutorial.kt. Paste the following code in this file to create an app template for the aggregation tutorials.安装驱动程序后，创建一个名为AggTutorial.kt的文件。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

package org.example

// Modify imports for each tutorial as needed.
import com.mongodb.client.model.*
import com.mongodb.kotlin.client.coroutine.MongoClient
import kotlinx.coroutines.runBlocking
import kotlinx.datetime.LocalDateTime
import kotlinx.datetime.toJavaLocalDateTime
import kotlinx.serialization.Contextual
import kotlinx.serialization.Serializable
import org.bson.Document
import org.bson.conversions.Bson

// Define data classes.
@Serializable
data class MyClass(
    ...
)

suspend fun main() {
    // Replace the placeholder with your connection string.
    val uri = "<connection string>"

    MongoClient.create(uri).use { mongoClient ->
        val aggDB = mongoClient.getDatabase("agg_tutorials_db")

        // Get a reference to relevant collections.
        // ... val someColl = ...

        // Delete any existing documents in collections if needed.
        // ... someColl.deleteMany(empty())

        // Insert sample data into the collection or collections.
        // ... someColl.insertMany( ... )

        // Create an empty pipeline.
        val pipeline = mutableListOf<Bson>()

        // Add code to create pipeline stages.
        // ... pipeline.add(...)

        // Run the aggregation.
        // ... val aggregationResult = someColl.aggregate<Document>(pipeline)

        // Print the aggregation results.
        aggregationResult.collect { println(it) }
    }
}

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

val uri = "mongodb+srv://mongodb-example:27017"

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

First, create Kotlin data classes to model the data in the persons collection:首先，创建Kotlin数据类来对persons集合中的数据进行建模：

@Serializable
data class Address(
    val number: Int,
    val street: String,
    val city: String
)

@Serializable
data class Person(
    val personID: String,
    val firstname: String,
    val lastname: String,
    @Contextual val dateOfBirth: LocalDateTime,
    val vocation: String,
    val address: Address,
    val gender: String? = null
)

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

val persons = aggDB.getCollection<Person>("persons")
persons.deleteMany(Filters.empty())

persons.insertMany(
    listOf(
        Person(
            "6392529400",
            "Elise",
            "Smith",
            LocalDateTime.parse("1972-01-13T09:32:07"),
            "ENGINEER",
            Address(5625, "Tipa Circle", "Wojzinmoj")
        ),
        Person(
            "1723338115",
            "Olive",
            "Ranieri",
            LocalDateTime.parse("1985-05-12T23:14:30"),
            "ENGINEER",
            Address(9303, "Mele Circle", "Tobihbo"),
            "FEMALE"
        ),
        Person(
            "8732762874",
            "Toni",
            "Jones",
            LocalDateTime.parse("1991-11-23T16:53:56"),
            "POLITICIAN",
            Address(1, "High Street", "Upper Abbeywoodington")
        ),
        Person(
            "7363629563",
            "Bert",
            "Gooding",
            LocalDateTime.parse("1941-04-07T22:11:52"),
            "FLORIST",
            Address(13, "Upper Bold Road", "Redringtonville")
        ),
        Person(
            "1029648329",
            "Sophie",
            "Celements",
            LocalDateTime.parse("1959-07-06T17:35:45"),
            "ENGINEER",
            Address(5, "Innings Close", "Basilbridge")
        ),
        Person(
            "7363626383",
            "Carl",
            "Simmons",
            LocalDateTime.parse("1998-12-26T13:13:55"),
            "ENGINEER",
            Address(187, "Hillside Road", "Kenningford")
        )
    )
)

Create the Template App创建模板应用程序

Before you begin following this aggregation tutorial, you must set up a new Node.js app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习本聚合教程之前，您必须设置一个新的Node.js应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the driver, create a file to run the tutorial template. Paste the following code in this file to create an app template for the aggregation tutorials.安装驱动程序后，创建一个文件来运行教程模板。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

const { MongoClient } = require('mongodb');
// Replace the placeholder with your connection string.
const uri = '<connection-string>';
const client = new MongoClient(uri);
export async function run() {
  try {
    const aggDB = client.db('agg_tutorials_db');

    // Get a reference to relevant collections.
    // ... const someColl =
    // ... const anotherColl =

    // Delete any existing documents in collections.
    // ... await someColl.deleteMany({});

    // Insert sample data into the collection or collections.
    // ... const someData = [ ... ];
    // ... await someColl.insertMany(someData);

    // Create an empty pipeline array.
    const pipeline = [];

    // Add code to create pipeline stages.
    // ... pipeline.push({ ... })

    // Run the aggregation.
    // ... const aggregationResult = ...

    // Print the aggregation results.
    for await (const document of aggregationResult) {
      console.log(document);
    }
  } finally {
    await client.close();
  }
}

run().catch(console.dir);

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

const uri = "mongodb+srv://mongodb-example:27017";

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

const persons = aggDB.collection('persons');

await persons.insertMany([
  {
    person_id: '6392529400',
    firstname: 'Elise',
    lastname: 'Smith',
    dateofbirth: new Date('1972-01-13T09:32:07Z'),
    vocation: 'ENGINEER',
    address: {
      number: 5625,
      street: 'Tipa Circle',
      city: 'Wojzinmoj',
    },
  },
  {
    person_id: '1723338115',
    firstname: 'Olive',
    lastname: 'Ranieri',
    dateofbirth: new Date('1985-05-12T23:14:30Z'),
    gender: 'FEMALE',
    vocation: 'ENGINEER',
    address: {
      number: 9303,
      street: 'Mele Circle',
      city: 'Tobihbo',
    },
  },
  {
    person_id: '8732762874',
    firstname: 'Toni',
    lastname: 'Jones',
    dateofbirth: new Date('1991-11-23T16:53:56Z'),
    vocation: 'POLITICIAN',
    address: {
      number: 1,
      street: 'High Street',
      city: 'Upper Abbeywoodington',
    },
  },
  {
    person_id: '7363629563',
    firstname: 'Bert',
    lastname: 'Gooding',
    dateofbirth: new Date('1941-04-07T22:11:52Z'),
    vocation: 'FLORIST',
    address: {
      number: 13,
      street: 'Upper Bold Road',
      city: 'Redringtonville',
    },
  },
  {
    person_id: '1029648329',
    firstname: 'Sophie',
    lastname: 'Celements',
    dateofbirth: new Date('1959-07-06T17:35:45Z'),
    vocation: 'ENGINEER',
    address: {
      number: 5,
      street: 'Innings Close',
      city: 'Basilbridge',
    },
  },
  {
    person_id: '7363626383',
    firstname: 'Carl',
    lastname: 'Simmons',
    dateofbirth: new Date('1998-12-26T13:13:55Z'),
    vocation: 'ENGINEER',
    address: {
      number: 187,
      street: 'Hillside Road',
      city: 'Kenningford',
    },
  },
]);

Create the Template App创建模板应用程序

Before you begin following this aggregation tutorial, you must set up a new PHP app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习本聚合教程之前，您必须设置一个新的PHP应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the library, create a file called agg_tutorial.php. Paste the following code in this file to create an app template for the aggregation tutorials.安装库后，创建一个名为agg_tutorial.php的文件。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

<?php

require 'vendor/autoload.php';

// Modify imports for each tutorial as needed.
use MongoDB\Client;
use MongoDB\BSON\UTCDateTime;
use MongoDB\Builder\Pipeline;
use MongoDB\Builder\Stage;
use MongoDB\Builder\Type\Sort;
use MongoDB\Builder\Query;
use MongoDB\Builder\Expression;
use MongoDB\Builder\Accumulator;

use function MongoDB\object;

// Replace the placeholder with your connection string.
$uri = '<connection string>';
$client = new Client($uri);

// Get a reference to relevant collections.
// ... $someColl = $client->agg_tutorials_db->someColl;
// ... $anotherColl = $client->agg_tutorials_db->anotherColl;

// Delete any existing documents in collections if needed.
// ... $someColl->deleteMany([]);

// Insert sample data into the collection or collections.
// ... $someColl->insertMany(...);

// Add code to create pipeline stages within the Pipeline instance.
// ... $pipeline = new Pipeline(...);

// Run the aggregation.
// ... $cursor = $someColl->aggregate($pipeline);

// Print the aggregation results.
foreach ($cursor as $doc) {
    echo json_encode($doc, JSON_PRETTY_PRINT), PHP_EOL;
}

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

$uri = 'mongodb+srv://mongodb-example:27017';

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

$persons = $client->agg_tutorials_db->persons;
$persons->deleteMany([]);

$persons->insertMany(
    [
        [
            'person_id' => '6392529400',
            'firstname' => 'Elise',
            'lastname' => 'Smith',
            'dateofbirth' => new UTCDateTime(new DateTimeImmutable('1972-01-13T09:32:07')),
            'vocation' => 'ENGINEER',
            'address' => ['number' => 5625, 'Street' => 'Tipa Circle', 'city' => 'Wojzinmoj'],
        ],
        [
            'person_id' => '1723338115',
            'firstname' => 'Olive',
            'lastname' => 'Ranieri',
            'gender' => 'FEMALE',
            'dateofbirth' => new UTCDateTime(new DateTimeImmutable('1985-05-12T23:14:30')),
            'vocation' => 'ENGINEER',
            'address' => ['number' => 9303, 'street' => 'Mele Circle', 'city' => 'Tobihbo'],
        ],
        [
            'person_id' => '8732762874',
            'firstname' => 'Toni',
            'lastname' => 'Jones',
            'dateofbirth' => new UTCDateTime(new DateTimeImmutable('1991-11-23T16:53:56')),
            'vocation' => 'POLITICIAN',
            'address' => ['number' => 1, 'street' => 'High Street', 'city' => 'Upper Abbeywoodington'],
        ],
        [
            'person_id' => '7363629563',
            'firstname' => 'Bert',
            'lastname' => 'Gooding',
            'dateofbirth' => new UTCDateTime(new DateTimeImmutable('1941-04-07T22:11:52')),
            'vocation' => 'FLORIST',
            'address' => ['number' => 13, 'street' => 'Upper Bold Road', 'city' => 'Redringtonville'],
        ],
        [
            'person_id' => '1029648329',
            'firstname' => 'Sophie',
            'lastname' => 'Celements',
            'dateofbirth' => new UTCDateTime(new DateTimeImmutable('1959-07-06T17:35:45')),
            'vocation' => 'ENGINEER',
            'address' => ['number' => 5, 'street' => 'Innings Close', 'city' => 'Basilbridge'],
        ],
        [
            'person_id' => '7363626383',
            'firstname' => 'Carl',
            'lastname' => 'Simmons',
            'dateofbirth' => new UTCDateTime(new DateTimeImmutable('1998-12-26T13:13:55')),
            'vocation' => 'ENGINEER',
            'address' => ['number' => 187, 'street' => 'Hillside Road', 'city' => 'Kenningford'],
        ]
    ]
);

Create the Template App创建模板应用程序

Before you begin following this aggregation tutorial, you must set up a new Python app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习本聚合教程之前，您必须设置一个新的Python应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the library, create a file called agg_tutorial.py. Paste the following code in this file to create an app template for the aggregation tutorials.安装库后，创建一个名为agg_tutorial.py的文件。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

# Modify imports for each tutorial as needed.
from pymongo import MongoClient

# Replace the placeholder with your connection string.
uri = "<connection-string>"
client = MongoClient(uri)

try:
    agg_db = client["agg_tutorials_db"]

    # Get a reference to relevant collections.
    # ... some_coll = agg_db["some_coll"]
    # ... another_coll = agg_db["another_coll"]

    # Delete any existing documents in collections if needed.
    # ... some_coll.delete_many({})

    # Insert sample data into the collection or collections.
    # ... some_coll.insert_many(...)

    # Create an empty pipeline array.
    pipeline = []

    # Add code to create pipeline stages.
    # ... pipeline.append({...})

    # Run the aggregation.
    # ... aggregation_result = ...

    # Print the aggregation results.
    for document in aggregation_result:
        print(document)

finally:
    client.close()

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

uri = "mongodb+srv://mongodb-example:27017"

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

person_coll = agg_db["persons"]

person_data = [
    {
        "person_id": "6392529400",
        "firstname": "Elise",
        "lastname": "Smith",
        "dateofbirth": datetime(1972, 1, 13, 9, 32, 7),
        "vocation": "ENGINEER",
        "address": {
            "number": 5625,
            "street": "Tipa Circle",
            "city": "Wojzinmoj",
        },
    },
    {
        "person_id": "1723338115",
        "firstname": "Olive",
        "lastname": "Ranieri",
        "dateofbirth": datetime(1985, 5, 12, 23, 14, 30),
        "gender": "FEMALE",
        "vocation": "ENGINEER",
        "address": {
            "number": 9303,
            "street": "Mele Circle",
            "city": "Tobihbo",
        },
    },
    {
        "person_id": "8732762874",
        "firstname": "Toni",
        "lastname": "Jones",
        "dateofbirth": datetime(1991, 11, 23, 16, 53, 56),
        "vocation": "POLITICIAN",
        "address": {
            "number": 1,
            "street": "High Street",
            "city": "Upper Abbeywoodington",
        },
    },
    {
        "person_id": "7363629563",
        "firstname": "Bert",
        "lastname": "Gooding",
        "dateofbirth": datetime(1941, 4, 7, 22, 11, 52),
        "vocation": "FLORIST",
        "address": {
            "number": 13,
            "street": "Upper Bold Road",
            "city": "Redringtonville",
        },
    },
    {
        "person_id": "1029648329",
        "firstname": "Sophie",
        "lastname": "Celements",
        "dateofbirth": datetime(1959, 7, 6, 17, 35, 45),
        "vocation": "ENGINEER",
        "address": {
            "number": 5,
            "street": "Innings Close",
            "city": "Basilbridge",
        },
    },
    {
        "person_id": "7363626383",
        "firstname": "Carl",
        "lastname": "Simmons",
        "dateofbirth": datetime(1998, 12, 26, 13, 13, 55),
        "vocation": "ENGINEER",
        "address": {
            "number": 187,
            "street": "Hillside Road",
            "city": "Kenningford",
        },
    },
]

person_coll.insert_many(person_data)

Create the Template App创建模板应用程序

Before you begin following this aggregation tutorial, you must set up a new Ruby app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习本聚合教程之前，您必须设置一个新的Ruby应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the driver, create a file called agg_tutorial.rb. Paste the following code in this file to create an app template for the aggregation tutorials.安装驱动程序后，创建一个名为agg_tutorial.rb的文件。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

# typed: strict
require 'mongo'
require 'bson'

# Replace the placeholder with your connection string.
uri = "<connection string>"

Mongo::Client.new(uri) do |client|

  agg_db = client.use('agg_tutorials_db')

  # Get a reference to relevant collections.
  # ... some_coll = agg_db[:some_coll]

  # Delete any existing documents in collections if needed.
  # ... some_coll.delete_many({})

  # Insert sample data into the collection or collections.
  # ... some_coll.insert_many( ... )

  # Add code to create pipeline stages within the array.
  # ... pipeline = [ ... ]

  # Run the aggregation.
  # ... aggregation_result = some_coll.aggregate(pipeline)

  # Print the aggregation results.
  aggregation_result.each do |doc|
    puts doc
  end

end

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

uri = "mongodb+srv://mongodb-example:27017"

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

persons = agg_db[:persons]
persons.delete_many({})

persons.insert_many(
  [
    {
      person_id: "6392529400",
      firstname: "Elise",
      lastname: "Smith",
      dateofbirth: DateTime.parse("1972-01-13T09:32:07Z"),
      vocation: "ENGINEER",
      address: {
        number: 5625,
        street: "Tipa Circle",
        city: "Wojzinmoj",
      },
    },
    {
      person_id: "1723338115",
      firstname: "Olive",
      lastname: "Ranieri",
      dateofbirth: DateTime.parse("1985-05-12T23:14:30Z"),
      gender: "FEMALE",
      vocation: "ENGINEER",
      address: {
        number: 9303,
        street: "Mele Circle",
        city: "Tobihbo",
      },
    },
    {
      person_id: "8732762874",
      firstname: "Toni",
      lastname: "Jones",
      dateofbirth: DateTime.parse("1991-11-23T16:53:56Z"),
      vocation: "POLITICIAN",
      address: {
        number: 1,
        street: "High Street",
        city: "Upper Abbeywoodington",
      },
    },
    {
      person_id: "7363629563",
      firstname: "Bert",
      lastname: "Gooding",
      dateofbirth: DateTime.parse("1941-04-07T22:11:52Z"),
      vocation: "FLORIST",
      address: {
        number: 13,
        street: "Upper Bold Road",
        city: "Redringtonville",
      },
    },
    {
      person_id: "1029648329",
      firstname: "Sophie",
      lastname: "Celements",
      dateofbirth: DateTime.parse("1959-07-06T17:35:45Z"),
      vocation: "ENGINEER",
      address: {
        number: 5,
        street: "Innings Close",
        city: "Basilbridge",
      },
    },
    {
      person_id: "7363626383",
      firstname: "Carl",
      lastname: "Simmons",
      dateofbirth: DateTime.parse("1998-12-26T13:13:55Z"),
      vocation: "ENGINEER",
      address: {
        number: 187,
        street: "Hillside Road",
        city: "Kenningford",
      },
    },
  ]
)

Create the Template App创建模板应用程序

Before you begin following this aggregation tutorial, you must set up a new Rust app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习本聚合教程之前，您必须设置一个新的Rust应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the driver, create a file called agg-tutorial.rs. Paste the following code in this file to create an app template for the aggregation tutorials.安装驱动程序后，创建一个名为agg-tutorial.rs的文件。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

use mongodb::{
    bson::{doc, Document},
    options::ClientOptions,
    Client,
};
use futures::stream::TryStreamExt;
use std::error::Error;

// Define structs.
// #[derive(Debug, Serialize, Deserialize)]
// struct MyStruct { ... }

#[tokio::main]
async fn main() mongodb::error::Result<()> {
    // Replace the placeholder with your connection string.
    let uri = "<connection string>";
    let client = Client::with_uri_str(uri).await?;

    let agg_db = client.database("agg_tutorials_db");

    // Get a reference to relevant collections.
    // ... let some_coll: Collection<T> = agg_db.collection("...");
    // ... let another_coll: Collection<T> = agg_db.collection("...");

    // Delete any existing documents in collections if needed.
    // ... some_coll.delete_many(doc! {}).await?;

    // Insert sample data into the collection or collections.
    // ... some_coll.insert_many(vec![...]).await?;

    // Create an empty pipeline.
    let mut pipeline = Vec::new();

    // Add code to create pipeline stages.
    // pipeline.push(doc! { ... });

    // Run the aggregation and print the results.
    let mut results = some_coll.aggregate(pipeline).await?;
    while let Some(result) = results.try_next().await? {
       println!("{:?}\n", result);
    }
    Ok(())
}

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

let uri = "mongodb+srv://mongodb-example:27017";

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

First, create Rust structs to model the data in the persons collection:首先，创建Rust结构体来对persons集合中的数据进行建模：

#[derive(Debug, Serialize, Deserialize)]
struct Address {
    number: i32,
    street: String,
    city: String,
}

#[derive(Debug, Serialize, Deserialize)]
struct Person {
    person_id: String,
    firstname: String,
    lastname: String,
    dateofbirth: DateTime,
    vocation: String,
    address: Address,
}

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

let persons: Collection<Person> = agg_db.collection("persons");
persons.delete_many(doc! {}).await?;

let data = vec![
    Person {
        person_id: "6392529400".to_string(),
        firstname: "Elise".to_string(),
        lastname: "Smith".to_string(),
        dateofbirth: DateTime::builder().year(1972).month(1).day(13).hour(9).minute(32).second(7).build().unwrap(),
        vocation: "ENGINEER".to_string(),
        address: Address {
            number: 5625,
            street: "Tipa Circle".to_string(),
            city: "Wojzinmoj".to_string(),
        },
    },
    Person {
        person_id: "1723338115".to_string(),
        firstname: "Olive".to_string(),
        lastname: "Ranieri".to_string(),
        gender: "FEMALE".to_string(),
        dateofbirth: DateTime::builder().year(1985).month(5).day(12).hour(23).minute(14).second(30).build().unwrap(),
        vocation: "ENGINEER".to_string(),
        address: Address {
            number: 9303,
            street: "Mele Circle".to_string(),
            city: "Tobihbo".to_string(),
        },
    },
    Person {
        person_id: "8732762874".to_string(),
        firstname: "Toni".to_string(),
        lastname: "Jones".to_string(),
        dateofbirth: DateTime::builder().year(1991).month(11).day(23).hour(16).minute(53).second(56).build().unwrap(),
        vocation: "POLITICIAN".to_string(),
        address: Address {
            number: 1,
            street: "High Street".to_string(),
            city: "Upper Abbeywoodington".to_string(),
        },
    },
    Person {
        person_id: "7363629563".to_string(),
        firstname: "Bert".to_string(),
        lastname: "Gooding".to_string(),
        dateofbirth: DateTime::builder().year(1941).month(4).day(7).hour(22).minute(11).second(52).build().unwrap(),
        vocation: "FLORIST".to_string(),
        address: Address {
            number: 13,
            street: "Upper Bold Road".to_string(),
            city: "Redringtonville".to_string(),
        },
    },
    Person {
        person_id: "1029648329".to_string(),
        firstname: "Sophie".to_string(),
        lastname: "Celements".to_string(),
        dateofbirth: DateTime::builder().year(1959).month(7).day(6).hour(17).minute(35).second(45).build().unwrap(),
        vocation: "ENGINEER".to_string(),
        address: Address {
            number: 5,
            street: "Innings Close".to_string(),
            city: "Basilbridge".to_string(),
        },
    },
    Person {
        person_id: "7363626383".to_string(),
        firstname: "Carl".to_string(),
        lastname: "Simmons".to_string(),
        dateofbirth: DateTime::builder().year(1998).month(12).day(26).hour(13).minute(13).second(55).build().unwrap(),
        vocation: "ENGINEER".to_string(),
        address: Address {
            number: 187,
            street: "Hillside Road".to_string(),
            city: "Kenningford".to_string(),
        },
    },
];

persons.insert_many(data).await?;

Create the Template App创建模板应用程序

Before you begin following an aggregation tutorial, you must set up a new Scala app. You can use this app to connect to a MongoDB deployment, insert sample data into MongoDB, and run the aggregation pipeline.在开始学习聚合教程之前，您必须设置一个新的Scala应用程序。您可以使用此应用程序连接到MongoDB部署，将示例数据插入MongoDB，并运行聚合管道。

After you install the driver, create a file called AggTutorial.scala. Paste the following code in this file to create an app template for the aggregation tutorials.安装驱动程序后，创建一个名为AggTutorial.scala的文件。将以下代码粘贴到此文件中，为聚合教程创建应用程序模板。

package org.example;

// Modify imports for each tutorial as needed.
import org.mongodb.scala.MongoClient
import org.mongodb.scala.bson.Document
import org.mongodb.scala.model.{Accumulators, Aggregates, Field, Filters, Variable}

import java.text.SimpleDateFormat

object FilteredSubset {

  def main(args: Array[String]): Unit = {

    // Replace the placeholder with your connection string.
    val uri = "<connection string>"
    val mongoClient = MongoClient(uri)
    Thread.sleep(1000)

    val aggDB = mongoClient.getDatabase("agg_tutorials_db")

    // Get a reference to relevant collections.
    // ... val someColl = aggDB.getCollection("someColl")
    // ... val anotherColl = aggDB.getCollection("anotherColl")

    // Delete any existing documents in collections if needed.
    // ... someColl.deleteMany(Filters.empty()).subscribe(...)

    // If needed, create the date format template.
    val dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss")

    // Insert sample data into the collection or collections.
    // ... someColl.insertMany(...).subscribe(...)

    Thread.sleep(1000)

    // Add code to create pipeline stages within the Seq.
    // ... val pipeline = Seq(...)

    // Run the aggregation and print the results.
    // ... someColl.aggregate(pipeline).subscribe(...)

    Thread.sleep(1000)
    mongoClient.close()
  }
}

For every tutorial, you must replace the connection string placeholder with your deployment's connection string.对于每个教程，您必须将连接字符串占位符替换为部署的连接字符串。

For example, if your connection string is "mongodb+srv://mongodb-example:27017", your connection string assignment resembles the following:例如，如果连接字符串是"mongodb+srv://mongodb-example:27017"，连接字符串分配类似于以下内容：

val uri = "mongodb+srv://mongodb-example:27017"

Create the Collection创建集合

This example uses a persons collection, which contains documents describing each person's name, date of birth, vocation, and other details. The aggregation selects documents based on whether their field values match specified criteria.此示例使用persons集合，其中包含描述每个人的姓名、出生日期、职业和其他详细信息的文档。聚合根据文档的字段值是否与指定条件匹配来选择文档。

To create the persons collection and insert the sample data, add the following code to your application:要创建persons集合并插入示例数据，请将以下代码添加到应用程序中：

val persons = aggDB.getCollection("persons")

persons.deleteMany(Filters.empty()).subscribe(
  _ => {},
  e => println("Error: " + e.getMessage),
)

val dateFormat = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss")

persons.insertMany(Seq(
  Document(
    "person_id" -> "6392529400",
    "firstname" -> "Elise",
    "lastname" -> "Smith",
    "dateofbirth" -> dateFormat.parse("1972-01-13T09:32:07"),
    "vocation" -> "ENGINEER",
    "address" -> Document(
      "number" -> 5625,
      "street" -> "Tipa Circle",
      "city" -> "Wojzinmoj"
    )
  ),
  Document(
    "person_id" -> "1723338115",
    "firstname" -> "Olive",
    "lastname" -> "Ranieri",
    "dateofbirth" -> dateFormat.parse("1985-05-12T23:14:30"),
    "gender" -> "FEMALE",
    "vocation" -> "ENGINEER",
    "address" -> Document(
      "number" -> 9303,
      "street" -> "Mele Circle",
      "city" -> "Tobihbo"
    )
  ),
  Document(
    "person_id" -> "8732762874",
    "firstname" -> "Toni",
    "lastname" -> "Jones",
    "dateofbirth" -> dateFormat.parse("1991-11-23T16:53:56"),
    "vocation" -> "POLITICIAN",
    "address" -> Document(
      "number" -> 1,
      "street" -> "High Street",
      "city" -> "Upper Abbeywoodington"
    )
  ),
  Document(
    "person_id" -> "7363629563",
    "firstname" -> "Bert",
    "lastname" -> "Gooding",
    "dateofbirth" -> dateFormat.parse("1941-04-07T22:11:52"),
    "vocation" -> "FLORIST",
    "address" -> Document(
      "number" -> 13,
      "street" -> "Upper Bold Road",
      "city" -> "Redringtonville"
    )
  ),
  Document(
    "person_id" -> "1029648329",
    "firstname" -> "Sophie",
    "lastname" -> "Celements",
    "dateofbirth" -> dateFormat.parse("1959-07-06T17:35:45"),
    "vocation" -> "ENGINEER",
    "address" -> Document(
      "number" -> 5,
      "street" -> "Innings Close",
      "city" -> "Basilbridge"
    )
  ),
  Document(
    "person_id" -> "7363626383",
    "firstname" -> "Carl",
    "lastname" -> "Simmons",
    "dateofbirth" -> dateFormat.parse("1998-12-26T13:13:55"),
    "vocation" -> "ENGINEER",
    "address" -> Document(
      "number" -> 187,
      "street" -> "Hillside Road",
      "city" -> "Kenningford"
    )
  )
)).subscribe(
  _ => {},
  e => println("Error: " + e.getMessage),
)