cursor.count()

发布于 2015-09-14 14:47:17 | 163 次阅读 | 评论: 0 | 来源: 网络整理

cursor.count()¶

The count() method counts the number of documents referenced by a cursor. Append the count() method to a find() query to return the number of matching documents, as in the following prototype:

db.collection.find().count()

This operation does not actually perform the find(); instead, the operation counts the results that would be returned by the find().

The count() can accept the following argument:

参数:	applySkipLimit (boolean) – Optional. Specifies whether to consider the effects of the `cursor.skip()` and `cursor.limit()` methods in the count. By default, the `count()` method ignores the effects of the `cursor.skip()` and `cursor.limit()`. Set `applySkipLimit` to `true` to consider the effect of these methods. 也可以参考 `cursor.size()`

MongoDB also provides the shell wrapper db.collection.count() for the db.collection.find().count() construct.

Consider the following examples of the count() method:

Count the number of all documents in the orders collection:
```
db.orders.find().count()
```
Count the number of the documents in the orders collection with the field ord_dt greater than new Date('01/01/2012'):
```
db.orders.find( { ord_dt: { $gt: new Date('01/01/2012') } } ).count()
```
Count the number of the documents in the orders collection with the field ord_dt greater than new Date('01/01/2012') taking into account the effect of the limit(5):
```
db.orders.find( { ord_dt: { $gt: new Date('01/01/2012') } } ).limit(5).count(true)
```

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