使用条件获取MongoDB中集合的大小？
首先让我们创建一个包含文档的集合-
> dbmongoDBCollectionSizeDemoinsertOne({"Name":"John", "Age":23});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cf23e3db64a577be5a2bc16")
}
> dbmongoDBCollectionSizeDemoinsertOne({"Name":"Chris", "Age":24});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cf23e45b64a577be5a2bc17")
}
> dbmongoDBCollectionSizeDemoinsertOne({"Name":"Robert", "Age":26});
{
"acknowledged" : true,
"insertedId" : ObjectId("5cf23e4db64a577be5a2bc18")
}以下是在find()方法的帮助下显示集合中所有文档的查询-
> dbmongoDBCollectionSizeDemofind();
这将产生以下文件-
{ "_id" : ObjectId("5cf23e3db64a577be5a2bc16"), "Name" : "John", "Age" : 23 }
{ "_id" : ObjectId("5cf23e45b64a577be5a2bc17"), "Name" : "Chris", "Age" : 24 }
{ "_id" : ObjectId("5cf23e4db64a577be5a2bc18"), "Name" : "Robert", "Age" : 26 }以下是使用条件获取集合大小的查询-
> var collectionsize = 0;
> dbmongoDBCollectionSizeDemofind({Name:'Robert'})forEach(function(d) {
var s = Objectbsonsize(d);
collectionsize=collectionsize +s;
})
> print(collectionsize);这将产生以下文件-
52