在MongoDB中，可以使用db.collection.deleteMany()方法从集合中删除现有文档。此方法根据过滤器从集合中删除多个文档。
deleteMany()是一个mongo shell方法，可以删除多个文档。此方法可用于多文档交易中。如果在上限集合中使用此方法，则它将引发异常。
Syntax:
Parameters:
fileter: First parameter of this method. It specifies the selection criteria for the delete using query operators. The type of this parameter is document. If it contains empty document, i.e, {}, then this method will delete all the documents from the collection.
Optional Parameters:
- writeConcern: It is only used when you do not want to use the default write concern. The type of this parameter is document.
- collation: It specifies the use of the collation for operations. It allows users to specify the language-specific rules for string comparison like rules for lettercase and accent marks. The type of this parameter is document.
Return: This method will return a document that contains a boolean acknowledged as true (if the write concern is enabled) or false (if the write concern is disabled) and deletedCount that represents the total number of deleted documents.
例子：
在以下示例中，我们正在使用：
db.collection.deleteMany(
,
{
writeConcern: ,
collation:
}
) 
删除与过滤器匹配的文档：
在此示例中，我们将从与过滤器匹配的贡献者集合中删除多个文档，即语言：“ C＃”。换句话说，我们正在从数据库中删除那些使用C＃语言的贡献者。 
删除所有文件：
db.collection.deleteMany()方法中传递空文档来从贡献者集合中删除所有文档。
Database: GeeksforGeeks
Collection: contributor
Document: four documents that contain the details of the contributors in the form of field-value pairs.