MongoDB未插入全部文档：插入8条仅显示5条的问题

我尝试向MongoDB的mycollection集合插入8个文档，插入操作的确认消息显示已成功插入8个文档，但执行db.mycollection.countDocuments()仅返回5，使用MongoDB Compass GUI查看也得到同样结果。

插入代码 #

db.mycollection.insertMany(
   [  {
    "_id": "e89c4c7a-bfdc-4433-bf68-2b3ea4deaad6",
    "name": "Dunn England",
    "isActive": false,
    "balance": "1,505.70",
    "picture": "http://placehold.it/32x32",
    "age": 25,
    "eyeColor": "brown",
    "gender": "male"
  },
  {
    "_id": "4b5cc8e8-6683-4dd9-a0c3-dd683c41c32f",
    "name": "Elizabeth Cunning",
    "isActive": false,
    "balance": "505.70",
    "picture": "http://placehold.it/32x32",
    "age": 19,
    "eyeColor": "brown",
    "gender": "female"
  },
  {
    "_id": "808259cb-0ea3-4424-b626-c147655625fc",
    "name": "Gabrielle Dane",
    "isActive": true,
    "balance": "5505.70",
    "picture": "http://placehold.da/32x32",
    "age": 38,
    "eyeColor": "blue",
    "gender": "female"
  },
  {
    "_id": "26a0278a-d825-42f9-a697-47a53f69e0c5",
    "name": "Renee Morrow",
    "isActive": true,
    "balance": "2,022.81",
    "picture": "http://placehold.it/32x32",
    "age": 24,
    "eyeColor": "green",
    "gender": "female"
  },
  {
    "_id": "d631ff57-c77c-4447-bad9-37b2147ed18f",
    "name": "Jake Roberts",
    "isActive": false,
    "balance": "6022.81",
    "picture": "http://placehold.it/32x32",
    "age": 24,
    "eyeColor": "green",
    "gender": "male"
  },
  {
    "_id": "48b7a108-07c9-4107-aed8-637756caa430",
    "name": "Urmina Roberts",
    "isActive": true,
    "balance": "7,6022.81",
    "picture": "http://placehold.it/32x32",
    "age": 24,
    "eyeColor": "green",
    "gender": "female"
  },
  {
    "_id": "3a75d9dc-ef66-452b-9e12-9dcda2a33977",
    "name": "Emily Waters",
    "isActive": false,
    "balance": "76022.81",
    "picture": "http://placehold.ww/34x34",
    "age": 44,
    "eyeColor": "brown",
    "gender": "female"
  },
  {
    "_id": "b01a9244-28b5-4c89-90d5-70fb1ec573e2",
    "name": "Scott Turner",
    "isActive": true,
    "balance": "1,894.19",
    "picture": "http://placehold.dk/32x32",
    "age": 88,
    "eyeColor": "green",
    "gender": "male"
  }]
)

插入确认与计数结果 #

acknowledged: true,
  insertedIds: {
    '0': 'e89c4c7a-bfdc-4433-bf68-2b3ea4deaad6',
    '1': '4b5cc8e8-6683-4dd9-a0c3-dd683c41c32f',
    '2': '808259cb-0ea3-4424-b626-c147655625fc',
    '3': '26a0278a-d825-42f9-a697-47a53f69e0c5',
    '4': 'd631ff57-c77c-4447-bad9-37b2147ed18f',
    '5': '48b7a108-07c9-4107-aed8-637756caa430',
    '6': '3a75d9dc-ef66-452b-9e12-9dcda2a33977',
    '7': 'b01a9244-28b5-4c89-90d5-70fb1ec573e2'
}

local> db.mycollection.countDocuments()
5

问题原因与解决方法 #

核心原因 #

你执行计数命令时的命令行前缀是local>，说明当前操作的是local数据库，但插入文档时大概率是在其他数据库（比如默认的test数据库）下执行的。MongoDB的集合属于特定数据库，跨数据库查询自然无法看到目标数据。

解决步骤 #

1. 切换回插入文档时使用的数据库（以默认的test为例）：

use test

2. 再次执行计数命令：

db.mycollection.countDocuments()

3. 规范操作：后续插入或查询时，先明确切换到目标数据库，避免跨库操作混淆。

额外检查 #

在MongoDB Compass中，确认当前连接的数据库与插入文档时的数据库一致，重新查询集合即可看到全部8个文档。

内容的提问来源于stack exchange，提问作者codingjoe