BSON Types

痛定思痛。 2022-06-01 12:54 154阅读 0赞

# BSON Types #

On this page

*  [ObjectId][]
 *  [String][]
 *  [Timestamps][]
 *  [Date][]

[BSON][] 是一个二进制序列化格式，在MongoDB里面被用来做文档存储和远程程序调用。 BSON 规格说明位于 [bsonspec.org][].

每个BSON 类型都有数字和字符标识，如下表所列:

<table style="border-width:0px; margin-top:24px; margin-right:0px; margin-left:0px; font-size:14px; line-height:24px; color:rgb(73,71,71); font-family:Akzidenz,'Helvetica Neue',Helvetica,Arial,sans-serif">       
 <thead> 
  <tr> 
   <th style="text-align:left; padding:0px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Type</th> 
   <th style="text-align:left; padding:0px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Number</th> 
   <th style="text-align:left; padding:0px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Alias</th> 
   <th style="text-align:left; padding:0px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Notes</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Double</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 1</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “double”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> String</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 2</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “string”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Object</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 3</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “object”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Array</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 4</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “array”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Binary data</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 5</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “binData”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Undefined</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 6</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “undefined”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Deprecated.</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> ObjectId</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 7</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “objectId”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Boolean</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 8</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “bool”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Date</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 9</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “date”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Null</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 10</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “null”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Regular Expression</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 11</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “regex”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> DBPointer</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 12</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “dbPointer”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Deprecated.</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> JavaScript</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 13</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “javascript”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Symbol</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 14</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “symbol”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Deprecated.</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> JavaScript (with scope)</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 15</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “javascriptWithScope”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 32-bit integer</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 16</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “int”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Timestamp</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 17</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “timestamp”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 64-bit integer</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 18</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “long”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Decimal128</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 19</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “decimal”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> New in version 3.4.</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Min key</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> -1</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “minKey”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
  <tr> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> Max key</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> 127</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> “maxKey”</td> 
   <td style="padding:11px 5px 12px; border-top:0px rgb(235,235,237); border-right:0px rgb(235,235,237); border-left:0px rgb(235,235,237); border-bottom-color:rgb(235,235,237)"> &nbsp;</td> 
  </tr> 
 </tbody> 
</table>

你可以使用 [`$type`][type] 操作符和这些值根据BSON 类型来查询文档.  [`$type`][type 1]聚合操作符返回操作符表达式[operator expression][] 使用的 已有BSON 类型字符.

想要确定一个属性的类型，查看 [Check Types in the mongo Shell][].

如果你想从 BSON 转换成JSON, 查看[Extended JSON][] .

下列章节是特殊BSON 类型的注意事项.

## ObjectId ##

ObjectIds 很小, 几乎是唯一的, 可以快速创建而且有序的. ObjectId 的值由12 字节组成, 前4个字节是一个反映ObjectId 创建时间的时间戳. Specifically:

*  a 4-byte 从Unix 纪元开始的秒数,
 *  a 3-byte 机器ID标识,
 *  a 2-byte 进程ID, and
 *  a 3-byte 从一个随机数开始的计数器.

MongoDB中每个集合中的文档都需要一个唯一的 [\_id][id] 作为主键 [primary key][].如果插入的文档省略了 `_id` 属性, MongoDB 会 自动创建一个 值为[ObjectId][]的 \_id属性 .

这同样适用于设置属性 [upsert: true][upsert_ true]的更新操作.

MongoDB clients 应该为 `_id` 属性添加一个唯一的 ObjectId. 使用ObjectIds 作为 `_id` 属性有下列好处:

*  在 [`mongo`][mongo] shell中, 你可以使用 [`ObjectId.getTimestamp()`][ObjectId.getTimestamp] 方法获取ObjectId的创建时间.
 *  在使用`ObjectId` 的`_id` 属性上排序相当于在创建时间上排序 .
    
    IMPORTANT
    
    The relationship between the order of `ObjectId` values and generation time is not strict within a single second. If multiple systems, or multiple processes or threads on a single system generate values, within a single second; `ObjectId` values do not represent a strict insertion order. Clock skew between clients can also result in non-strict ordering even for values because client drivers generate `ObjectId` values.

SEE ALSO

[`ObjectId()`][ObjectId 1]

## String ##

BSON 字符编码是 UTF-8. 通常情况下， 每种语言的驱动在序列化和反序列化BSON时都会转换成UTF-8编码. 这样，BSON 可以轻松存储大多数国际化字符. [\[1\]][1] 另外，MongoDB [`$regex`][regex] 正则表达式查询中的正则字符串支持UTF-8.

## 时间戳 ##

BSON 有一个MongoDB内部使用的特殊时间戳类型 ，并且和常规的时间类型没关系[Date][Date 1]. 时间戳的值是一个 64 位值:

*  前32 位是 `time_t` (从Unix 纪元开始的秒数)
 *  后32 位是一个在某一秒内操作的可增长的序数.

在一个 [`mongod`][mongod] 实例中, 时间戳的值是唯一的.

在副本集中,  [oplog][] 有一个`ts` 属性. 这个属性的值是BSON 时间戳类型，表示操作的时间.

NOTE

BSON 时间戳类型是MongoDB 内部使用. 大多数情况下，你可以使用 BSON日期类型. 更多信息查看[Date][Date 1] .

I如果你插入一个在一级字段中包含空BSON时间戳的文档，MongoDB服务器将会使用当前的时间戳值替换空的时间戳。例如，如果你使用下面的操作插入一个包含时间戳值的文档:

var a = new Timestamp();
    
    db.test.insertOne( {
           ts: a } );

`然后，db.test.find()` 操作会返回一个类型下面的文档:

{
           "_id" : ObjectId("542c2b97bac0595474108b48"), "ts" : Timestamp(1412180887, 1) }

`如果ts` 是一个内嵌文档的属性,  服务器将会继续让其保持空的时间戳值.

*在 2.6改版以前: * 服务器只会替换插入文档内前两个字段中（包括\`\`\_id\`\`）的空时间戳值。现在，MongoDB将会对任何一级字段中的空时间戳进行替换.

## Date ##

BSON日期是一个64位整数，表示当前距离Unix新纪元（1970年1月1日）的毫秒数。这样就保证了过去和未来2.9亿年的可表示日期范围.

The [official BSON specification][] refers to the BSON Date type as the *UTC datetime*.

BSON 日期类型有符号. [\[2\]][2] 负值表示 1970前的日期.

EXAMPLE

Construct a Date using the `new Date()` constructor in the [`mongo`][mongo] shell:

var mydate1 = new Date()

EXAMPLE

Construct a Date using the `ISODate()` constructor in the [`mongo`][mongo] shell:

var mydate2 = ISODate()

EXAMPLE

Return the `Date` value as string:

mydate1.toString()

EXAMPLE

Return the month portion of the Date value; months are zero-indexed, so that January is month `0`:

mydate1.getMonth()

<table style="background-color:transparent; border-width:0px; font-size:14px; line-height:24px; margin-top:24px; margin-right:0px; margin-left:0px">     
 <tbody> 
  <tr> 
   <td style="padding:11px 5px 12px; border-color:rgb(235,235,237); border-width:0px!important; border-style:!important"> <a href="https://docs.mongodb.com/manual/reference/bson-types/#id4" style="color:rgb(0,108,188)" rel="nofollow">[2]</a></td> 
   <td style="padding:11px 5px 12px; border-color:rgb(235,235,237); border-width:0px!important; border-style:!important"> <span style="color:rgb(73,71,71); font-family:Akzidenz,&quot;Helvetica Neue&quot;,Helvetica,Arial,sans-serif; font-size:14px; background-color:rgb(255,255,255)">在2.0版本之前，&nbsp;</span><span>日期</span><span style="color:rgb(73,71,71); font-family:Akzidenz,&quot;Helvetica Neue&quot;,Helvetica,Arial,sans-serif; font-size:14px; background-color:rgb(255,255,255)">&nbsp;值被错误地表示为&nbsp;</span><span style="color:rgb(73,71,71); font-family:Akzidenz,&quot;Helvetica Neue&quot;,Helvetica,Arial,sans-serif; font-size:14px; background-color:rgb(255,255,255)">无符号整数</span><span style="color:rgb(73,71,71); font-family:Akzidenz,&quot;Helvetica Neue&quot;,Helvetica,Arial,sans-serif; font-size:14px; background-color:rgb(255,255,255)">，大大地影响了&nbsp;</span><span>日期</span><span style="color:rgb(73,71,71); font-family:Akzidenz,&quot;Helvetica Neue&quot;,Helvetica,Arial,sans-serif; font-size:14px; background-color:rgb(255,255,255)">&nbsp;字段上的排序、范围查询以及索引。由于在升级过程中不会重建索引，所以如果您是在早期版本中在&nbsp;</span><span>日期</span><span style="color:rgb(73,71,71); font-family:Akzidenz,&quot;Helvetica Neue&quot;,Helvetica,Arial,sans-serif; font-size:14px; background-color:rgb(255,255,255)">&nbsp;字段上创建的索引，请对与应用相关的、1970年前的日期进行重新索引</span>.</td> 
  </tr> 
 </tbody> 
</table>

[ObjectId]: https://docs.mongodb.com/manual/reference/bson-types/#objectid
[String]: https://docs.mongodb.com/manual/reference/bson-types/#string
[Timestamps]: https://docs.mongodb.com/manual/reference/bson-types/#timestamps
[Date]: https://docs.mongodb.com/manual/reference/bson-types/#date
[BSON]: https://docs.mongodb.com/manual/reference/glossary/#term-bson
[bsonspec.org]: http://bsonspec.org/
[type]: https://docs.mongodb.com/manual/reference/operator/query/type/#op._S_type
[type 1]: https://docs.mongodb.com/manual/reference/operator/aggregation/type/#exp._S_type
[operator expression]: https://docs.mongodb.com/manual/meta/aggregation-quick-reference/#agg-quick-ref-operator-expressions
[Check Types in the mongo Shell]: https://docs.mongodb.com/manual/core/shell-types/#check-types-in-shell
[Extended JSON]: https://docs.mongodb.com/manual/reference/mongodb-extended-json/
[id]: https://docs.mongodb.com/manual/reference/glossary/#term-id
[primary key]: https://docs.mongodb.com/manual/reference/glossary/#term-primary-key
[upsert_ true]: https://docs.mongodb.com/manual/reference/method/db.collection.update/#upsert-parameter
[mongo]: https://docs.mongodb.com/manual/reference/program/mongo/#bin.mongo
[ObjectId.getTimestamp]: https://docs.mongodb.com/manual/reference/method/ObjectId.getTimestamp/#ObjectId.getTimestamp
[ObjectId 1]: https://docs.mongodb.com/manual/reference/method/ObjectId/#ObjectId
[1]: https://docs.mongodb.com/manual/reference/bson-types/#sort-string-internationalization
[regex]: https://docs.mongodb.com/manual/reference/operator/query/regex/#op._S_regex
[Date 1]: https://docs.mongodb.com/manual/reference/bson-types/#document-bson-type-date
[mongod]: https://docs.mongodb.com/manual/reference/program/mongod/#bin.mongod
[oplog]: https://docs.mongodb.com/manual/reference/glossary/#term-oplog
[official BSON specification]: http://bsonspec.org/#/specification
[2]: https://docs.mongodb.com/manual/reference/bson-types/#unsigned-date