使用mgo按id查找

huangapple
go评论120阅读模式
英文:

Find by id with mgo

问题

我想通过_id查找数据。我知道这个数据存在，而且这个_id也存在（我已经用pymongo测试过）。

但是下面的代码找不到它：

  1. type id_cookie struct {
  2.     IdCookie int
  3. }
  5. func get_id_mongo() int {
  6.     session, err := mgo.Dial("127.0.0.1")
  7.     if err != nil {
  8.         panic(err)
  9.     }
  10.     defer session.Close()
  12.     // Optional. Switch the session to a monotonic behavior.
  13.     session.SetMode(mgo.Monotonic, true)
  15.     c := session.DB("id_bag").C("id_cookie")
  16.     data := id_cookie{}
  17.     err2 := c.FindId(bson.M{"_id": bson.ObjectIdHex("58593d1d6aace357b32bb3a1")}).One(&data)
  18.     if (err2 != nil){
  19.         Info.Println("error")
  20.         Info.Println(err2)
  21.     }
  22.     Info.Println(data)
  23.     return data.IdCookie
  24. }

它只返回一个0。

但是我可以使用pytmongo和Python找到它。

  1. import requests
  2. import pymongo 
  3. from pymongo import MongoClient
  4. from bson.objectid import ObjectId
  5. from pprint import pprint
  6. client = MongoClient('127.0.0.1', 27017)
  8. import base64
  12. db = client.id_bag
  13. pprint(db.collection_names())
  14. result = db.id_cookie.insert_one(
  15.     { 'IdCookie': 1
  16.     })
  17. print(result.inserted_id)
  19. data = db.id_cookie.find_one({"_id": ObjectId("58593d1d6aace357b32bb3a1")})
  20. print(data)

以下是结果：

  1. ['id_cookie', 'system.indexes']
  2. 58593d2d6aace357b32bb3a3
  3. {'IdCookie': 1, '_id': ObjectId('58593d1d6aace357b32bb3a1')}

有人有任何想法吗？

编辑：
我尝试了以下代码：

  1. err2 := c.FindId(bson.ObjectIdHex("58593d1d6aace357b32bb3a1")).One(&data)

但是我仍然得到0：

  1. INFO: 2016/12/20 15:42:08 Cookie_Id.go:147: 1
  2. INFO: 2016/12/20 15:42:08 Cookie_Id.go:149: 2
  3. INFO: 2016/12/20 15:42:18 Cookie_Id.go:87: data
  4. INFO: 2016/12/20 15:42:18 Cookie_Id.go:88: {0}
  5. INFO: 2016/12/20 15:42:18 Cookie_Id.go:89: 0
  6. INFO: 2016/12/20 15:42:18 Cookie_Id.go:118: 0
  7. INFO: 2016/12/20 15:42:18 Cookie_Id.go:128: OK
英文:

I would like to find a data by _id. I know that this data exists and that this _id exist (I've tested it with pymongo).

But the code below doesn't find it:

  1. type id_cookie struct {
  2. 	IdCookie int
  3. }
  5. func get_id_mongo() int {
  6. 	session, err := mgo.Dial("127.0.0.1")
  7. 	if err != nil {
  8. 		panic(err)
  9. 	}
  10. 	defer session.Close()
  12. 	// Optional. Switch the session to a monotonic behavior.
  13. 	session.SetMode(mgo.Monotonic, true)
  15. 	c := session.DB("id_bag").C("id_cookie")
  16. 	data := id_cookie{}
  17. 	err2 := c.FindId(bson.M{"_id": bson.ObjectIdHex("58593d1d6aace357b32bb3a1")}).One(&data)
  18. 	if (err2 != nil){
  19. 		Info.Println("error")
  20. 		Info.Println(err2)
  21. 	}
  22. 	Info.Println(data)
  23. 	return data.IdCookie
  24. }

It just returns me a 0.

But I can find it using pytmongo and python.

  1. import requests
  2. import pymongo 
  3. from pymongo import MongoClient
  4. from bson.objectid import ObjectId
  5. from pprint import pprint
  6. client = MongoClient('127.0.0.1', 27017)
  8. import base64
  12. db = client.id_bag
  13. pprint(db.collection_names())
  14. result = db.id_cookie.insert_one(
  15.     { 'IdCookie': 1
  16.     })
  17. print(result.inserted_id)
  19. data = db.id_cookie.find_one({"_id": ObjectId("58593d1d6aace357b32bb3a1")})
  20. print(data)

here are the result :

  1. ['id_cookie', 'system.indexes']
  2. 58593d2d6aace357b32bb3a3
  3. {'IdCookie': 1, '_id': ObjectId('58593d1d6aace357b32bb3a1')}

Does anyone have any idea?

Edit :
i've try with :

  1. err2 := c.FindId(bson.ObjectIdHex("58593d1d6aace357b32bb3a1")).One(&data)

but i still have 0 :

  1. INFO: 2016/12/20 15:42:08 Cookie_Id.go:147: 1
  2. INFO: 2016/12/20 15:42:08 Cookie_Id.go:149: 2
  3. INFO: 2016/12/20 15:42:18 Cookie_Id.go:87: data
  4. INFO: 2016/12/20 15:42:18 Cookie_Id.go:88: {0}
  5. INFO: 2016/12/20 15:42:18 Cookie_Id.go:89: 0
  6. INFO: 2016/12/20 15:42:18 Cookie_Id.go:118: 0
  7. INFO: 2016/12/20 15:42:18 Cookie_Id.go:128: OK

答案1

得分: 16

你可以使用Collection.FindId()，然后只传递id值，或者使用Collection.Find()，然后需要指定字段名和值：

  1. err2 := c.FindId(bson.ObjectIdHex("58593d1d6aace357b32bb3a1")).One(&data)
  3. // 或者
  4. err2 := c.Find(bson.M{"_id": bson.ObjectIdHex("58593d1d6aace357b32bb3a1")}).
  5.     One(&data)

如果没有错误，那就表示找到了文档。

如果你总是看到打印出来的值是0（作为id_cookie.IdCookie字段的值），那就表示文档中保存这个id的字段名不同。

使用结构体标签来告诉它在MongoDB中是如何存储的。例如，如果在你的MongoDB中它被称为"myid"，你可以这样映射它：

  1. type id_cookie struct {
  2.     IdCookie int `bson:"myid"`
  3. }

还要注意的是，你不应该每次查询数据时都连接到MongoDB服务器，而是连接一次，然后重复使用会话。详细信息请参考：链接

英文:

You either use Collection.FindId() and then you pass only the id value, or you use Collection.Find() and then you have to specify a value with the field name too:

  1. err2 := c.FindId(bson.ObjectIdHex("58593d1d6aace357b32bb3a1")).One(&data)
  3. // OR
  4. err2 := c.Find(bson.M{"_id": bson.ObjectIdHex("58593d1d6aace357b32bb3a1")}).
  5.     One(&data)

If you get no errors, that means the document is found.

If you always see 0 printed (as the value of the id_cookie.IdCookie field), that means the field in the document holding this id has a different name.

Use struct tags to tell how it is stored in your MongoDB. E.g. if in your MongoDB it is called "myid", you can map it like this:

  1. type id_cookie struct {
  2.     IdCookie int `bson:"myid"`
  3. }

Also note that you should not connect to the MongoDB server every time you want to query some data, instead connect once, and just reuse the session. for details see: https://stackoverflow.com/questions/40999637/mgo-query-performance-seems-consistently-slow-500-650ms/41000876#41000876

huangapple
  • 本文由 发表于 2016年12月20日 21:56:03
  • 转载请务必保留本文链接：https://go.coder-hub.com/41244024.html
  • go
  • mgo
  • mongodb
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