## Mongodb 字段类型对映表

| Type Name  |  Type Number |
| ------------ | ------------ |
| Double  |  1 |
| String  | 2  |
| Object | 3 |
| Array | 4 |
| Binary data | 5 |
| Object id | 7 |
| Boolean | 8 |
| Date | 9 |
| Null | 10 |
| Regular expression | 11 |
| JavaScript code | 13 |
| Symbol  | 14 |
| JavaScript code with scope | 15 |
| 32-bit integer | 16 | 
| Timestamp | 17 |
| 64-bit integer | 18 |
| Min key | 255 |
| Max key | 127 |

## 把 published_at 字段 str 类型从改为 Date 类型 

``` .shell
db.bitcoin.find( { 'published_at' : { $type : 2 } } ).forEach( function (x) {   
  x.published_at = new Date(x.published_at); // convert field to string
  db.bitcoin.save(x);
});
```

[参考链接](https://stackoverflow.com/questions/4973095/how-to-change-the-type-of-a-field "参考链接")

怎么修改 mongodb 字段类型

## MongoDB 一些比较烦人的警告信息

---

### 比如 /sys/kernel/mm/transparent_hugepage/defrag is 'always' ：
```.shell
CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
CONTROL  [initandlisten] **        We suggest setting it to 'never'
CONTROL  [initandlisten]
```

### 解决 ：
```.shell
sudo apt install sysfsutils

echo "kernel/mm/transparent_hugepage/enabled = never" >> /etc/sysfs.conf
echo "kernel/mm/transparent_hugepage/defrag = never" >> /etc/sysfs.conf

 /etc/init.d/sysfsutils restart
```

[参考链接](https://askubuntu.com/questions/597372/how-do-i-modify-sys-kernel-mm-transparent-hugepage-enabled "参考链接")

怎么修改 mongodb 字段类型

解决 MongoDB 一些的警告信息

GitHub