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Go MongoDB Driver 实例

2024-08-14 23
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简介： Go MongoDB Driver 实例

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所有的 API 可以在 Go MongoDB Driver 找到。

在下面的例子中，都使用下面的这个 db() 函数来获取 mongo.Database 的实例。

import (
  "context"
  "go.mongodb.org/mongo-driver/mongo"
  "go.mongodb.org/mongo-driver/mongo/options"
  "log"
)
func db() *mongo.Database {
    clientOptions := options.Client().ApplyURL("mongodb://localhost:27017")
    client, err := mongo.Connect(context.TODO(), clientOptions)
    if err != nil {
        log.Fatal(err)
    }
    err = client.Ping(context.TODO(), nil)
    if err != nil {
        log.Fatal(err)
    }
    return client.Database("test")
}

实例一 插入单条记录

import (
  "context"
  "fmt"
  "go.mongodb.org/mongo-driver/bson"
  "go.mongodb.org/mongo-driver/mongo"
  "go.mongodb.org/mongo-driver/mongo/options"
  "log"
)
func main() {
  db := db()
  coll := db.Collection("inventory_test")
  coll.Drop(context.TODO())
  // E represents a BSON element for a D. It is usually used inside a D.
  // type E struct {
  //   Key   string
  //   Value interface{}
  // }
  result, err := coll.InsertOne(
    context.TODO(),
    // bson.D 是一个 []bson.E 类型
    bson.D{
      {"item", "canvas"},  // 这是一个 bson.E 类型元素
      {"qty", 100},
      {"tags", bson.A{"cotton"}},
      {"size", bson.D{
        {"h", 28},
        {"w", 35.5},
        {"uom", "cm"},
      }},
    },
  )
  if err != nil {
    panic(err)
  }
  fmt.Printf("Inserted ID is %+v\n", result.InsertedID)
  
  // 我们会在 MongoDB 中看到如下内容：
  // {
  //     "_id": ObjectId("5e64e556478fb77672d8b5b5"),
  //     "item": "canvas",
  //     "qty": NumberInt("100"),
  //     "tags": [
  //         "cotton"
  //     ],
  //     "size": {
  //         "h": NumberInt("28"),
  //         "w": 35.5,
  //         "uom": "cm"
  //     }
  // }
}

实例二 查询单条记录

import (
  "context"
  "fmt"
  "go.mongodb.org/mongo-driver/bson"
  "go.mongodb.org/mongo-driver/mongo"
  "go.mongodb.org/mongo-driver/mongo/options"
  "log"
)
type Size struct {
  H   int
  W   float64
  Uom string
}
type InventoryTest struct {
  ID   string `bson:"_id"`
  Item string
  Qty  int
  Tags []string
  Size Size
}
func main() {
  db := db()
  coll := db.Collection("inventory_test")
  cursor, err := coll.Find(
    context.TODO(),
    bson.D{
      {"item", "canvas"},
    },
  )
  if err != nil {
    panic(err)
  }
  var inventoryTest InventoryTest
    // 获取游标的下一条记录
  cursor.Next(context.TODO())
  err = cursor.Decode(&inventoryTest)
  if err != nil {
    panic(err)
  }
  fmt.Printf("inventoryTest is %+v\n", inventoryTest)
    // inventoryTest is {ID:5e64ea4919abb0178c2787f8 Item:canvas Qty:100 Tags:[cotton] Size:{H:28 W:35.5 Uom:cm}}
}

实例三 插入多条记录

import (
  "context"
  "fmt"
  "go.mongodb.org/mongo-driver/bson"
  "go.mongodb.org/mongo-driver/mongo"
  "go.mongodb.org/mongo-driver/mongo/options"
  "log"
)
func main() {
  db := db()
  coll := db.Collection("inventory_test")
  result, err := coll.InsertMany(
    context.TODO(),
    []interface{}{
      bson.D{
        {"item", "journal"},
        {"qty", int32(25)},
        {"tags", bson.A{"blank", "red"}},
        {"size", bson.D{
          {"h", 14},
          {"w", 21},
          {"uom", "cm"},
        }},
      },
      bson.D{
        {"item", "mat"},
        {"qty", int32(25)},
        {"tags", bson.A{"gray"}},
        {"size", bson.D{
          {"h", 27.9},
          {"w", 35.5},
          {"uom", "cm"},
        }},
      },
      bson.D{
        {"item", "mousepad"},
        {"qty", 25},
        {"tags", bson.A{"gel", "blue"}},
        {"size", bson.D{
          {"h", 19},
          {"w", 22.85},
          {"uom", "cm"},
        }},
      },
    },
  )
  if err != nil {
    panic(err)
  }
  fmt.Printf("InsertedIDs: %+v\n", result.InsertedIDs)
  // InsertedIDs: [ObjectID("5e64ee5bacce2998dc112460") ObjectID("5e64ee5bacce2998dc112461") ObjectID("5e64ee5bacce2998dc112462")]
}

实例四 查询顶层字段

package main
import (
  "context"
  "fmt"
  "go.mongodb.org/mongo-driver/bson"
  "go.mongodb.org/mongo-driver/bson/primitive"
  "go.mongodb.org/mongo-driver/mongo"
  "go.mongodb.org/mongo-driver/mongo/options"
  "log"
)
func db() *mongo.Database {
  clientOptions := options.Client().ApplyURI("mongodb://localhost:27017")
  client, err := mongo.Connect(context.TODO(), clientOptions)
  if err != nil {
    log.Fatal(err)
  }
  err = client.Ping(context.TODO(), nil)
  if err != nil {
    log.Fatal(err)
  }
  return client.Database("test")
}
type Size struct {
  H   int
  W   float64
  Uom string
}
type InventoryTest struct {
  ID   string `bson:"_id"`
  Item string
  Qty  int
  Tags []string
  Size Size
}
func main() {
  db := db()
  coll := db.Collection("inventory_query_top")
  err := coll.Drop(context.TODO())
  if err != nil {
    panic(err)
  }
  {
    // Start Example 6
    docs := []interface{}{
      bson.D{
        {"item", "journal"},
        {"qty", 25},
        {"size", bson.D{
          {"h", 14},
          {"w", 21},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
      bson.D{
        {"item", "notebook"},
        {"qty", 50},
        {"size", bson.D{
          {"h", 8.5},
          {"w", 11},
          {"uom", "in"},
        }},
        {"status", "A"},
      },
      bson.D{
        {"item", "paper"},
        {"qty", 100},
        {"size", bson.D{
          {"h", 8.5},
          {"w", 11},
          {"uom", "in"},
        }},
        {"status", "D"},
      },
      bson.D{
        {"item", "planner"},
        {"qty", 75},
        {"size", bson.D{
          {"h", 22.85},
          {"w", 30},
          {"uom", "cm"},
        }},
        {"status", "D"},
      },
      bson.D{
        {"item", "postcard"},
        {"qty", 45},
        {"size", bson.D{
          {"h", 10},
          {"w", 15.25},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
    }
    result, err := coll.InsertMany(context.TODO(), docs)
    if err != nil {
      panic(err)
    }
    fmt.Printf("InsertedIDs: %+v\n", result.InsertedIDs)
  }
  {
    // Start Example 7
    cursor, _ := coll.Find(
      context.TODO(),
      bson.D{},
    )
    length := 0
    for cursor.Next(context.TODO()) {
      length++
    }
    // 5
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 8
    cursor, _ := coll.Find(
      context.TODO(),
      bson.D{
        {"status", "D"},
      },
    )
    length := 0
    for cursor.Next(context.TODO()) {
      length++
    }
    // 2
    fmt.Printf("length: %+v\n", length)
  }
  {
    // Start Example 9
    cursor, _ := coll.Find(
      context.TODO(),
      bson.D{
        {"status", bson.D{{"$in", bson.A{"A", "D"}}}},
      },
    )
    length := 0
    for cursor.Next(context.TODO()) {
      length++
    }
    // 5
    fmt.Printf("length: %+v\n", length)
  }
  {
    // Start Example 10
    cursor, _ := coll.Find(
      context.TODO(),
      bson.D{
        {"status", "A"},
        {"qty", bson.D{{"$lt", 30}}},
      },
    )
    length := 0
    for cursor.Next(context.TODO()) {
      length++
    }
    // 1
    fmt.Printf("length: %+v\n", length)
  }
  {
    // Start Example 11
    cursor, _ := coll.Find(
      context.TODO(),
      bson.D{
        {"$or", bson.A{
          bson.D{{"status", "A"}},
          bson.D{{"qty", bson.D{{"$lt", 30}}}},
        }},
      },
    )
    length := 0
    for cursor.Next(context.TODO()) {
      length++
    }
    // 3
    fmt.Printf("length: %+v\n", length)
  }
  {
    // Start Example 12
    cursor, _ := coll.Find(
      context.TODO(),
      bson.D{
        {"status", "A"},
        {"$or", bson.A{
          bson.D{{"qty", bson.D{{"$lt", 30}}}},
          bson.D{{"item", primitive.Regex{Pattern: "^p", Options: ""}}},
        }},
      },
    )
    length := 0
    for cursor.Next(context.TODO()) {
      length++
    }
    // 2
    fmt.Printf("length: %+v\n", length)
  }
}

实例五 查询嵌套的字段

func main() {
  db := db()
  coll := db.Collection("inventory_query_embedded")
  err := coll.Drop(context.TODO())
  if err != nil {
    panic(err)
  }
  {
    // Start Example 14
    docs := []interface{}{
      bson.D{
        {"item", "journal"},
        {"qty", 25},
        {"size", bson.D{
          {"h", 14},
          {"w", 21},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
      bson.D{
        {"item", "notebook"},
        {"qty", 50},
        {"size", bson.D{
          {"h", 8.5},
          {"w", 11},
          {"uom", "in"},
        }},
        {"status", "A"},
      },
      bson.D{
        {"item", "paper"},
        {"qty", 100},
        {"size", bson.D{
          {"h", 8.5},
          {"w", 11},
          {"uom", "in"},
        }},
        {"status", "D"},
      },
      bson.D{
        {"item", "planner"},
        {"qty", 75},
        {"size", bson.D{
          {"h", 22.85},
          {"w", 30},
          {"uom", "cm"},
        }},
        {"status", "D"},
      },
      bson.D{
        {"item", "postcard"},
        {"qty", 45},
        {"size", bson.D{
          {"h", 10},
          {"w", 15.25},
          {"uom", "cm"},
        }},
      },
    }
    result, _ := coll.InsertMany(context.Background(), docs)
    fmt.Printf("InsertedIDs: %+v\n", result.InsertedIDs)
  }
  {
    // Start Example 15
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"size", bson.D{
          {"h", 14},
          {"w", 21},
          {"uom", "cm"},
        }},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 16
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"size", bson.D{
          {"w", 21},
          {"h", 14},
          {"uom", "cm"},
        }},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 17
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{{"size.uom", "in"}},
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 18
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"size.h", bson.D{
          {"$lt", 15},
        }},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 19
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"size.h", bson.D{
          {"$lt", 15},
        }},
        {"size.uom", "in"},
        {"status", "D"},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
}

实例六 查询数组

func main() {
  db := db()
  coll := db.Collection("inventory_query_array")
  err := coll.Drop(context.TODO())
  if err != nil {
    panic(err)
  }
  {
    // Start Example 20
    docs := []interface{}{
      bson.D{
        {"item", "journal"},
        {"qty", 25},
        {"tags", bson.A{"blank", "red"}},
        {"dim_cm", bson.A{14, 21}},
      },
      bson.D{
        {"item", "notebook"},
        {"qty", 50},
        {"tags", bson.A{"red", "blank"}},
        {"dim_cm", bson.A{14, 21}},
      },
      bson.D{
        {"item", "paper"},
        {"qty", 100},
        {"tags", bson.A{"red", "blank", "plain"}},
        {"dim_cm", bson.A{14, 21}},
      },
      bson.D{
        {"item", "planner"},
        {"qty", 75},
        {"tags", bson.A{"blank", "red"}},
        {"dim_cm", bson.A{22.85, 30}},
      },
      bson.D{
        {"item", "postcard"},
        {"qty", 45},
        {"tags", bson.A{"blue"}},
        {"dim_cm", bson.A{10, 15.25}},
      },
    }
    result, _ := coll.InsertMany(context.Background(), docs)
    fmt.Printf("InsertedIDs: %+v\n", result.InsertedIDs)
  }
  {
    // Start Example 21
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{{"tags", bson.A{"red", "blank"}}},
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 22
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"tags", bson.D{{"$all", bson.A{"red", "blank"}}}},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 23
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"tags", "red"},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 24
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"dim_cm", bson.D{
          {"$gt", 25},
        }},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 25
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"dim_cm", bson.D{
          {"$gt", 15},
          {"$lt", 20},
        }},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 26
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"dim_cm", bson.D{
          {"$elemMatch", bson.D{
            {"$gt", 22},
            {"$lt", 30},
          }},
        }},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 27
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"dim_cm.1", bson.D{
          {"$gt", 25},
        }},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 28
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"tags", bson.D{
          {"$size", 3},
        }},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
}

实例七 查询嵌套文档

func main() {
  db := db()
  coll := db.Collection("inventory_query_embedded")
  err := coll.Drop(context.TODO())
  if err != nil {
    panic(err)
  }
  {
    // Start Example 29
    docs := []interface{}{
      bson.D{
        {"item", "journal"},
        {"instock", bson.A{
          bson.D{
            {"warehouse", "A"},
            {"qty", 5},
          },
          bson.D{
            {"warehourse", "C"},
            {"qty", 15},
          },
        }},
      },
      bson.D{
        {"item", "notebook"},
        {"instock", bson.A{
          bson.D{
            {"warehouse", "C"},
            {"qty", 5},
          },
        }},
      },
      bson.D{
        {"item", "paper"},
        {"instock", bson.A{
          bson.D{
            {"warehouse", "A"},
            {"qty", 60},
          },
          bson.D{
            {"warehouse", "B"},
            {"qty", 15},
          },
        }},
      },
      bson.D{
        {"item", "planner"},
        {"instock", bson.A{
          bson.D{
            {"warehouse", "A"},
            {"qty", 40},
          },
          bson.D{
            {"warehouse", "B"},
            {"qty", 5},
          },
        }},
      },
      bson.D{
        {"item", "postcard"},
        {"instock", bson.A{
          bson.D{
            {"warehouse", "B"},
            {"qty", 15},
          },
          bson.D{
            {"warehouse", "C"},
            {"qty", 35},
          },
        }},
      },
    }
    result, _ := coll.InsertMany(context.Background(), docs)
    fmt.Printf("InsertedIDs: %+v\n", result.InsertedIDs)
  }
  {
    // Start Example 30
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"instock", bson.D{
          {"warehouse", "A"},
          {"qty", 5},
        }},
      })
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length) // 1
  }
  {
    // Start Example 31
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"instock", bson.D{
          {"qty", 5},
          {"warehouse", "A"},
        }},
      })
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length) // 0
  }
  {
    // Start Example 32
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"instock.0.qty", bson.D{
          {"$lte", 20},
        }},
      })
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length) // 3
  }
  {
    // Start Example 33
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"instock.qty", bson.D{
          {"$lte", 20},
        }},
      })
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length) // 5
  }
  {
    // Start Example 34
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"instock", bson.D{
          {"$elemMatch", bson.D{
            {"qty", 5},
            {"warehouse", "A"},
          }},
        }},
      })
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length) // 1
  }
  {
    // Start Example 35
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"instock", bson.D{
          {"$elemMatch", bson.D{
            {"qty", bson.D{
              {"$gt", 10},
              {"$lte", 20},
            }},
          }},
        }},
      })
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length) // 3
  }
  {
    // Start Example 36
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"instock.qty", bson.D{
          {"$gt", 10},
          {"$lte", 20},
        }},
      })
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length) // 4
  }
  {
    // Start Example 37
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"instock.qty", 5},
        {"instock.warehouse", "A"},
      })
    type Stock struct {
      Warehouse string
      Qty       int
    }
    type Data struct {
      Item    string
      Instock []Stock
    }
    length := 0
    for cursor.Next(context.Background()) {
      length++
      var d Data
      cursor.Decode(&d)
      // {Item:journal Instock:[{Warehouse:A Qty:5} {Warehouse: Qty:15}]}
      // {Item:planner Instock:[{Warehouse:A Qty:40} {Warehouse:B Qty:5}]}
      fmt.Printf("%+v\n", d)
    }
    fmt.Printf("length: %v\n", length) // 2
  }
}

实例八 查询为 null 或缺失的字段

func main() {
  db := db()
  coll := db.Collection("inventory_query_null_missing")
  err := coll.Drop(context.Background())
  if err != nil {
    panic(err)
  }
  {
    // Start Example 38
    docs := []interface{}{
      bson.D{
        {"_id", 1},
        {"item", nil},
      },
      bson.D{
        {"_id", 2},
      },
    }
    result, _ := coll.InsertMany(context.Background(), docs)
    fmt.Printf("InsertedIDs: %v\n", result.InsertedIDs)
  }
  {
    // Start Example 39
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"item", nil},
      })
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 40
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"item", bson.D{
          {"$type", 10}, // 10 等同于 "null", https://www.runoob.com/mongodb/mongodb-operators-type.html
        }},
      },
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
  {
    // Start Example 41
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"item", bson.D{
          {"$exists", false},
        }},
      })
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %v\n", length)
  }
}

实例九 Projection

func containsKey(doc bson.Raw, key ...string) bool {
  _, err := doc.LookupErr(key...)
  if err != nil {
    return false
  }
  return true
}
func main() {
  db := db()
  coll := db.Collection("inventory_project")
  err := coll.Drop(context.Background())
  if err != nil {
    panic(err)
  }
  {
    // Start Example 42
    docs := []interface{}{
      bson.D{
        {"item", "journal"},
        {"status", "A"},
        {"size", bson.D{
          {"h", 14},
          {"w", 21},
          {"uom", "cm"},
        }},
        {"instock", bson.A{
          bson.D{
            {"warehouse", "A"},
            {"qty", 5},
          },
        }},
      },
      bson.D{
        {"item", "notebook"},
        {"status", "A"},
        {"size", bson.D{
          {"h", 8.5},
          {"w", 11},
          {"uom", "in"},
        }},
        {"instock", bson.A{
          bson.D{
            {"warehouse", "EC"},
            {"qty", 5},
          },
        }},
      },
      bson.D{
        {"item", "paper"},
        {"status", "D"},
        {"size", bson.D{
          {"h", 8.5},
          {"w", 11},
          {"uom", "in"},
        }},
        {"instock", bson.A{
          bson.D{
            {"warehouse", "A"},
            {"qty", 60},
          },
        }},
      },
      bson.D{
        {"item", "postcard"},
        {"status", "A"},
        {"size", bson.D{
          {"h", 10},
          {"w", 15.25},
          {"uom", "cm"},
        }},
        {"instock", bson.A{
          bson.D{
            {"warehouse", "B"},
            {"qty", 15},
          },
          bson.D{
            {"warehouse", "EC"},
            {"qty", 35},
          },
        }},
      },
    }
    result, _ := coll.InsertMany(context.Background(), docs)
    fmt.Printf("InsertedIDs: %+v\n", result.InsertedIDs)
  }
  {
    // Start Example 43
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{{"status", "A"}},
    )
    length := 0
    for cursor.Next(context.Background()) {
      length++
    }
    fmt.Printf("length: %+v\n", length)
  }
  {
    // Start Example 44
    projection := bson.D{
      {"item", 1},
      {"status", 1},
    }
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"status", "A"},
      },
      options.Find().SetProjection(projection),
    )
    for cursor.Next(context.Background()) {
      doc := cursor.Current
      fmt.Printf("contain _id: %v\n", containsKey(doc, "_id"))
      fmt.Printf("contain item: %v\n", containsKey(doc, "item"))
      fmt.Printf("contain status: %v\n", containsKey(doc, "status"))
      fmt.Printf("contain size: %v\n", containsKey(doc, "size"))
      fmt.Printf("contain instock: %v\n", containsKey(doc, "instock"))
      break
    }
  }
  {
    // Start Example 45
    projection := bson.D{
      {"item", 1},
      {"status", 1},
      {"_id", 0},
    }
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"status", "A"},
      },
      options.Find().SetProjection(projection),
    )
    for cursor.Next(context.Background()) {
      doc := cursor.Current
      fmt.Printf("contain _id: %v\n", containsKey(doc, "_id"))
      fmt.Printf("contain item: %v\n", containsKey(doc, "item"))
      fmt.Printf("contain status: %v\n", containsKey(doc, "status"))
      fmt.Printf("contain size: %v\n", containsKey(doc, "size"))
      fmt.Printf("contain instock: %v\n", containsKey(doc, "instock"))
      break
    }
  }
  {
    // Start Example 46
    projection := bson.D{
      {"status", 0},
      {"instock", 0},
    }
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"status", "A"},
      },
      options.Find().SetProjection(projection),
    )
    for cursor.Next(context.Background()) {
      doc := cursor.Current
      fmt.Printf("contain _id: %v\n", containsKey(doc, "_id"))
      fmt.Printf("contain item: %v\n", containsKey(doc, "item"))
      fmt.Printf("contain status: %v\n", containsKey(doc, "status"))
      fmt.Printf("contain size: %v\n", containsKey(doc, "size"))
      fmt.Printf("contain instock: %v\n", containsKey(doc, "instock"))
      break
    }
  }
  {
    // Start Example 47
    projection := bson.D{
      {"item", 1},
      {"status", 1},
      {"size.uom", 1},
    }
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"status", "A"},
      },
      options.Find().SetProjection(projection),
    )
    for cursor.Next(context.Background()) {
      doc := cursor.Current
      fmt.Printf("contain _id: %v\n", containsKey(doc, "_id"))
      fmt.Printf("contain item: %v\n", containsKey(doc, "item"))
      fmt.Printf("contain status: %v\n", containsKey(doc, "status"))
      fmt.Printf("contain size: %v\n", containsKey(doc, "size"))
      fmt.Printf("contain instock: %v\n", containsKey(doc, "instock"))
      fmt.Printf("contain size.uom: %v\n", containsKey(doc, "size", "uom"))
      fmt.Printf("contain size.h: %v\n", containsKey(doc, "size", "h"))
      fmt.Printf("contain size.w: %v\n", containsKey(doc, "size", "w"))
      break
    }
  }
  {
    // Start Example 48
    projection := bson.D{
      {"size.uom", 0},
    }
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"status", "A"},
      },
      options.Find().SetProjection(projection),
    )
    for cursor.Next(context.Background()) {
      doc := cursor.Current
      fmt.Printf("contain _id: %v\n", containsKey(doc, "_id"))
      fmt.Printf("contain item: %v\n", containsKey(doc, "item"))
      fmt.Printf("contain status: %v\n", containsKey(doc, "status"))
      fmt.Printf("contain size: %v\n", containsKey(doc, "size"))
      fmt.Printf("contain instock: %v\n", containsKey(doc, "instock"))
      fmt.Printf("contain size.uom: %v\n", containsKey(doc, "size", "uom"))
      fmt.Printf("contain size.h: %v\n", containsKey(doc, "size", "h"))
      fmt.Printf("contain size.w: %v\n", containsKey(doc, "size", "w"))
      break
    }
  }
  {
    // Start Example 49
    projection := bson.D{
      {"item", 1},
      {"status", 1},
      {"instock.qty", 1},
    }
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"status", "A"},
      },
      options.Find().SetProjection(projection),
    )
    for cursor.Next(context.Background()) {
      doc := cursor.Current
      fmt.Printf("contain _id: %v\n", containsKey(doc, "_id"))
      fmt.Printf("contain item: %v\n", containsKey(doc, "item"))
      fmt.Printf("contain status: %v\n", containsKey(doc, "status"))
      fmt.Printf("contain size: %v\n", containsKey(doc, "size"))
      fmt.Printf("contain instock: %v\n", containsKey(doc, "instock"))
      instock, _ := doc.LookupErr("instock")
      vals, _ := instock.Array().Values()
      for _, val := range vals {
        subdoc := val.Document()
        elems, _ := subdoc.Elements()
        fmt.Printf("length of elems: %+v\n", len(elems))
      }
      break
    }
  }
  {
    // Start Example 50
    projection := bson.D{
      {"item", 1},
      {"status", 1},
      {"instock", bson.D{
        {"$slice", -1},
      }},
    }
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"status", "A"},
      },
      options.Find().SetProjection(projection),
    )
    for cursor.Next(context.Background()) {
      doc := cursor.Current
      fmt.Printf("contain _id: %v\n", containsKey(doc, "_id"))
      fmt.Printf("contain item: %v\n", containsKey(doc, "item"))
      fmt.Printf("contain status: %v\n", containsKey(doc, "status"))
      fmt.Printf("contain size: %v\n", containsKey(doc, "size"))
      fmt.Printf("contain instock: %v\n", containsKey(doc, "instock"))
      break
    }
  }
}

实例十 更新

func main() {
  db := db()
  coll := db.Collection("inventory_update")
  err := coll.Drop(context.Background())
  if err != nil {
    panic(err)
  }
  {
    // Start Example 51
    docs := []interface{}{
      bson.D{
        {"item", "canvas"},
        {"qty", 100},
        {"size", bson.D{
          {"h", 28},
          {"w", 35.5},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
      bson.D{
        {"item", "journal"},
        {"qty", 25},
        {"size", bson.D{
          {"h", 14},
          {"w", 21},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
      bson.D{
        {"item", "mat"},
        {"qty", 85},
        {"size", bson.D{
          {"h", 27.9},
          {"w", 35.5},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
      bson.D{
        {"item", "mousepad"},
        {"qty", 25},
        {"size", bson.D{
          {"h", 19},
          {"w", 22.85},
          {"uom", "in"},
        }},
        {"status", "P"},
      },
      bson.D{
        {"item", "notebook"},
        {"qty", 50},
        {"size", bson.D{
          {"h", 8.5},
          {"w", 11},
          {"uom", "in"},
        }},
        {"status", "P"},
      },
      bson.D{
        {"item", "paper"},
        {"qty", 100},
        {"size", bson.D{
          {"h", 8.5},
          {"w", 11},
          {"uom", "in"},
        }},
        {"status", "D"},
      },
      bson.D{
        {"item", "planner"},
        {"qty", 75},
        {"size", bson.D{
          {"h", 22.85},
          {"w", 30},
          {"uom", "cm"},
        }},
        {"status", "D"},
      },
      bson.D{
        {"item", "postcard"},
        {"qty", 45},
        {"size", bson.D{
          {"h", 10},
          {"w", 15.25},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
      bson.D{
        {"item", "sketchbook"},
        {"qty", 80},
        {"size", bson.D{
          {"h", 14},
          {"w", 21},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
      bson.D{
        {"item", "sketch pad"},
        {"qty", 95},
        {"size", bson.D{
          {"h", 22.85},
          {"w", 30.5},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
    }
    result, _ := coll.InsertMany(context.Background(), docs)
    fmt.Printf("InsertedIDs: %+v\n", result.InsertedIDs)
  }
  {
    // Start Example 52
    result, _ := coll.UpdateOne(
      context.Background(),
      bson.D{
        {"item", "paper"},
      },
      bson.D{
        {"$set", bson.D{
          {"size.uom", "cm"},
          {"status", "{"},
        }},
        {"$currentDate", bson.D{
          {"lastModified", true},
        }},
      },
    )
    fmt.Printf("result.MatchedCount: %+v\n", result.MatchedCount)
    fmt.Printf("result.ModifiedCount: %+v\n", result.ModifiedCount)
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"item", "paper"},
      },
    )
    for cursor.Next(context.Background()) {
      doc := cursor.Current
      uom, _ := doc.LookupErr("size", "uom")
      fmt.Printf("uom.StringValue() = %+v\n", uom.StringValue())
      status, _ := doc.LookupErr("status")
      fmt.Printf("status.StringValue() = %+v\n", status.StringValue())
      fmt.Printf("contain lastModified: %+v\n", containsKey(doc, "lastModified"))
    }
  }
  {
    // Start Example 53
    result, _ := coll.UpdateMany(
      context.Background(),
      bson.D{
        {"qty", bson.D{
          {"$lt", 50},
        }},
      },
      bson.D{
        {"$set", bson.D{
          {"size.uom", "cm"},
          {"status", "P"},
        }},
        {"$currentDate", bson.D{
          {"lastModified", true},
        }},
      },
    )
    fmt.Printf("result.MatchedCount: %+v\n", result.MatchedCount)
    fmt.Printf("result.ModifiedCount: %+v\n", result.ModifiedCount)
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"qty", bson.D{
          {"$lt", 50},
        }},
      },
    )
    for cursor.Next(context.Background()) {
      doc := cursor.Current
      uom, _ := doc.LookupErr("size", "uom")
      fmt.Printf("uom.StringValue(): %+v\n", uom.StringValue())
      status, _ := doc.LookupErr("status")
      fmt.Printf("status.StringValue(): %+v\n", status.StringValue())
      fmt.Printf("contain lastModified: %+v\n", containsKey(doc, "lastModified"))
    }
  }
  {
    // Start Example 54
    result, _ := coll.ReplaceOne(
      context.Background(),
      bson.D{
        {"item", "paper"},
      },
      bson.D{
        {"item", "paper"},
        {"instock", bson.A{
          bson.D{
            {"warehouse", "A"},
            {"qty", 60},
          },
          bson.D{
            {"warehouse", "B"},
            {"qty", 40},
          },
        }},
      },
    )
    fmt.Printf("MatchedCount: %+v\n", result.MatchedCount)
    fmt.Printf("ModifiedCount: %+v\n", result.ModifiedCount)
    cursor, _ := coll.Find(
      context.Background(),
      bson.D{
        {"item", "paper"},
      },
      )
    for cursor.Next(context.Background()) {
      doc := cursor.Current
      fmt.Printf("contains _id: %+v\n", containsKey(doc, "_id"))
      fmt.Printf("contains item: %+v\n", containsKey(doc, "item"))
      fmt.Printf("contain instock: %+v\n", containsKey(doc, "instock"))
      instock, _ := doc.LookupErr("instock")
      vals, _ := instock.Array().Values()
      fmt.Printf("length of vals is: %+v\n", vals)
    }
  }
}

实例十一 删除

func main() {
  db := db()
  coll := db.Collection("inventory_delete")
  err := coll.Drop(context.Background())
  if err != nil {
    panic(err)
  }
  {
    // Start Example 55
    docs := []interface{}{
      bson.D{
        {"item", "journal"},
        {"qty", 25},
        {"size", bson.D{
          {"h", 14},
          {"w", 21},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
      bson.D{
        {"item", "notebook"},
        {"qty", 50},
        {"size", bson.D{
          {"h", 8.5},
          {"w", 11},
          {"uom", "in"},
        }},
        {"status", "P"},
      },
      bson.D{
        {"item", "paper"},
        {"qty", 100},
        {"size", bson.D{
          {"h", 8.5},
          {"w", 11},
          {"uom", "in"},
        }},
        {"status", "D"},
      },
      bson.D{
        {"item", "planner"},
        {"qty", 75},
        {"size", bson.D{
          {"h", 22.85},
          {"w", 30},
          {"uom", "cm"},
        }},
        {"status", "D"},
      },
      bson.D{
        {"item", "postcard"},
        {"qty", 45},
        {"size", bson.D{
          {"h", 10},
          {"w", 15.25},
          {"uom", "cm"},
        }},
        {"status", "A"},
      },
    }
    result, _ := coll.InsertMany(context.Background(), docs)
    fmt.Printf("InsertedIDs: %+v\n", result.InsertedIDs)
  }
  {
    // Start Example 57
    result, _ := coll.DeleteMany(
      context.Background(),
      bson.D{
        {"status", "A"},
      },
    )
    fmt.Printf("Deleted count: %+v\n", result.DeletedCount)
  }
  {
    // Start Example 58
    result, _ := coll.DeleteOne(
      context.Background(),
      bson.D{
        {"status", "D"},
      },
    )
    fmt.Printf("Deleted count: %+v\n", result.DeletedCount)
  }
  {
    // Start Example 59
    result, _ := coll.DeleteMany(context.Background(), bson.D{})
    fmt.Printf("Deleted count: %+v\n", result.DeletedCount)
  }
}

实例十二 事务

var log = logger.New(logger.DebugLevel)
func main() {
  db := db()
  coll := db.Collection("inventory_delete")
  err := coll.Drop(context.Background())
  if err != nil {
    panic(err)
  }
  clientOptions := options.Client().ApplyURI("mongodb://localhost:27017")
  client, err := mongo.Connect(context.TODO(), clientOptions)
  if err != nil {
    log.Fatal(err)
  }
  employees := client.Database("hr").Collection("employees")
  events := client.Database("reporting").Collection("events")
  err = client.UseSession(context.Background(), func(sctx mongo.SessionContext) error {
    err := sctx.StartTransaction(options.Transaction().
      SetReadConcern(readconcern.Snapshot()).
      SetWriteConcern(writeconcern.New(writeconcern.WMajority())),
      )
    if err != nil {
      return err
    }
    _, err = employees.UpdateOne(sctx, bson.D{{"employee", 3}}, bson.D{{"$set", bson.D{{"status", "Inactive"}}}})
    if err != nil {
      sctx.AbortTransaction(sctx)
      log.Printf("caught exception during transaction, aborting.")
      return err
    }
    _, err = events.InsertOne(sctx, bson.D{{"employee", 3}, {"status", bson.D{{"new", "Inactive"}, {"old", "active"}}}})
    if err != nil {
      sctx.AbortTransaction(sctx)
      log.Printf("caught exception during transaction, aborting")
      return err
    }
    
    for {
      err = sctx.CommitTransaction(sctx)
      switch e := err.(type) {
      case nil:
        return nil
      case mongo.CommandError:
        if e.HasErrorLabel("UnknownTransactionCommitResult") {
          log.Printf("UnknownTransactionCommitResult, retrying commit operation...")
          continue
        }
        log.Printf("Error during commit...")
        return e
      default:
        log.Printf("Error during commit...")
        return e
      }
    }
  })
}

实例十三 事务 commit 重试

// RunTransactionWithRetry is an example function demonstrating transaction retry logic.
func RunTransactionWithRetry(sctx mongo.SessionContext, txnFn func(sessionContext mongo.SessionContext) error) error {
  for {
    err := txnFn(sctx) // Performs transaction.
    if err == nil {
      return nil
    }
    log.Printf("Transaction aborted. Caught exception during transaction.\n")
    // If transient error, retry the whole transaction
    if cmdErr, ok := err.(mongo.CommandError); ok && cmdErr.HasErrorLabel("TransientTransactionError") {
      log.Printf("TransientTransactionError, retrying transaction....")
      continue
    }
    return err
  }
}
// CommitWithRetry is an example function demonstrating transaction commit with retry logic.
func CommitWithRetry(sctx mongo.SessionContext) error {
  for {
    err := sctx.CommitTransaction(sctx)
    switch e := err.(type) {
    case nil:
      log.Printf("Transaction committed.")
      return nil
    case mongo.CommandError:
      // Can retry commit
      if e.HasErrorLabel("UnknownTransactionCommitResult") {
        log.Printf("UnknownTransactionCommitResult, retrying commit operation...")
        continue
      }
      log.Printf("Error during commit...")
      return e
    default:
      log.Printf("Error during commit...")
      return e
    }
  }
}
// TransactionsExamples contains examples for transaction operations.
func TransactionsExamples(ctx context.Context, client *mongo.Client) error {
  _, err := client.Database("hr").Collection("employees").InsertOne(ctx, bson.D{{"pi", 3.14159}})
  if err != nil {
    return err
  }
  _, err = client.Database("hr").Collection("employees").DeleteOne(ctx, bson.D{{"pi", 3.14159}})
  if err != nil {
    return err
  }
  _, err = client.Database("reporting").Collection("events").InsertOne(ctx, bson.D{{"pi", 3.14159}})
  if err != nil {
    return err
  }
  _, err = client.Database("reporting").Collection("events").DeleteOne(ctx, bson.D{{"pi", 3.14159}})
  if err != nil {
    return err
  }
  // Start Transactions Retry Example 3
  runTransactionWithRetry := func(sctx mongo.SessionContext, txnFn func(mongo.SessionContext) error) error {
    for {
      err := txnFn(sctx) // Performs transactions.
      if err == nil {
        return nil
      }
      log.Printf("Transaction aborted. Caught exception during transaction.")
      // If transient error, retry the whole transaction
      if cmdErr, ok := err.(mongo.CommandError); ok && cmdErr.HasErrorLabel("TransientTransactionError") {
        log.Printf("TransientTransactionError, retrying transaction...")
        continue
      }
      return err
    }
  }
  commitWithRetry := func(sctx mongo.SessionContext) error {
    for {
      err := sctx.CommitTransaction(sctx)
      switch e := err.(type) {
      case nil:
        log.Printf("Transaction committed.")
        return nil
      case mongo.CommandError:
        // Can retry commit
        if e.HasErrorLabel("UnknownTransactionCommitResult") {
          log.Printf("UnknownTransactionCommitResult, retrying commit operation...")
          continue
        }
        log.Printf("Error during commit...\n")
        return e
      default:
        log.Printf("Error during commit...\n")
        return e
      }
    }
  }
  // Updates two collections in a transaction.
  updateEmployeeInfo := func(sctx mongo.SessionContext) error {
    employees := client.Database("hr").Collection("employees")
    events := client.Database("reporting").Collection("events")
    err := sctx.StartTransaction(options.Transaction().
      SetReadConcern(readconcern.Snapshot()).
      SetWriteConcern(writeconcern.New(writeconcern.WMajority())),
    )
    if err != nil {
      return err
    }
    _, err = employees.UpdateOne(sctx, bson.D{{"employee", 3}}, bson.D{{"$set", bson.D{{"status", "Inactive"}}}})
    if err != nil {
      sctx.AbortTransaction(sctx)
      log.Printf("caught exception during transaction, aborting.")
      return err
    }
    _, err = events.InsertOne(sctx, bson.D{{"employee", 3}, {"status", bson.D{{"new", "Inactive"}, {"old", "Active"}}}})
    if err != nil {
      sctx.AbortTransaction(sctx)
      log.Printf("caught exception during transaction, aborting.")
      return err
    }
    return commitWithRetry(sctx)
  }
  return client.UseSessionWithOptions(
    ctx, options.Session().SetDefaultReadPreference(readpref.Primary()),
    func(sctx mongo.SessionContext) error {
      return runTransactionWithRetry(sctx, updateEmployeeInfo)
    },
  )
}

实例十四 ChangeStream

// ChangeStreamExamples contains examples of changestream operations.
func ChangeStreamExamples(t *testing.T, db *mongo.Database) {
  ctx := context.Background()
  coll := db.Collection("inventory_changestream")
  coll.Drop(context.Background())
  coll.InsertOne(ctx, bson.D{{"x", int32(1)}})
  var stop int32
  doInserts := func(coll *mongo.Collection) {
    for atomic.LoadInt32(&stop) == 0 {
      coll.InsertOne(ctx, bson.D{{"x", 1}})
      time.Sleep(10 * time.Microsecond)
      coll.DeleteOne(ctx, bson.D{{"x", 1}})
    }
  }
  go doInserts(coll)
  {
    // Start Changestream Example 1
    cs, err := coll.Watch(ctx, mongo.Pipeline{})
    defer cs.Close(ctx)
    ok := cs.Next(ctx)
    next := cs.Current
    fmt.Printf("%+v\n", err)
    fmt.Printf("%+v\n", ok)
    fmt.Printf("%+v\n", len(next))
  }
  {
    // Start Changestream Example 2
    cs, err := coll.Watch(ctx, mongo.Pipeline{}, options.ChangeStream().SetFullDocument(options.UpdateLookup))
    defer cs.Close(ctx)
    ok := cs.Next(ctx)
    next := cs.Current
    fmt.Printf("%+v\n", err)
    fmt.Printf("%+v\n", ok)
    fmt.Printf("%+v\n", len(next))
  }
  {
    original, err := coll.Watch(ctx, mongo.Pipeline{})
    defer original.Close(ctx)
    ok := original.Next(ctx)
    fmt.Printf("%+v\n", err)
    fmt.Printf("%+v\n", ok)
    resumeToken := original.ResumeToken()
    cs, err := coll.Watch(ctx, mongo.Pipeline{}, options.ChangeStream().SetResumeAfter(resumeToken))
    defer cs.Close(ctx)
    ok = cs.Next(ctx)
    result := cs.Current
    fmt.Printf("%+v\n", err)
    fmt.Printf("%+v\n", ok)
    fmt.Printf("%+v\n", len(result))
  }
  {
    pipeline := mongo.Pipeline{bson.D{{"$match", bson.D{{"$or",
      bson.A{
        bson.D{{"fullDocument.username", "alice"}},
        bson.D{{"operationType", "delete"}}}}},
    }}}
    cs, err := coll.Watch(ctx, pipeline)
    defer cs.Close(ctx)
    fmt.Printf("%+v\n", err)
    ok := cs.Next(ctx)
    next := cs.Current
    fmt.Printf("%+v\n", err)
    fmt.Printf("%+v\n", ok)
    fmt.Printf("%+v\n", len(next))
  }
}


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