在使用限制的同时，使用MongoDB获取总文档数吗？
您可以为此使用$facet运算符。为了理解这个概念，让我们创建一个带有文档的集合。创建带有文档的集合的查询如下-
> db.totalDocumentDemo.insertOne({"InstructorId":100,"InstructorName":"Larry","InstructorFav
ouriteSubject":["Java","MongoDB","Python"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c76e6701e9c5dd6f1f78274")
}
> db.totalDocumentDemo.insertOne({"InstructorId":200,"InstructorName":"Sam","InstructorFav
ouriteSubject":["SQL Server","C#","Javascript"]});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c76e69c1e9c5dd6f1f78275")
}在find()method的帮助下显示集合中的所有文档。查询如下-
> db.totalDocumentDemo.find().pretty();
输出结果
{
"_id" : ObjectId("5c76e6701e9c5dd6f1f78274"),
"InstructorId" : 100,
"InstructorName" : "Larry",
"InstructorFavouriteSubject" : [
"Java",
"MongoDB",
"Python"
]
}
{
"_id" : ObjectId("5c76e69c1e9c5dd6f1f78275"),
"InstructorId" : 200,
"InstructorName" : "Sam",
"InstructorFavouriteSubject" : [
"SQL Server",
"C#",
"Javascript"
]
}这是从集合中获取总文档数的查询-
> db.totalDocumentDemo.aggregate([
... {
... $facet:{
... Alldata:[{$match:{}}],
... totalDocument: [{ $count: 'totalDocument' }]
... }
... }
... ]).pretty();以下是显示文档数量的输出-
输出结果
{
"Alldata" : [
{
"_id" : ObjectId("5c76e6701e9c5dd6f1f78274"),
"InstructorId" : 100,
"InstructorName" : "Larry",
"InstructorFavouriteSubject" : [
"Java",
"MongoDB",
"Python"
]
},
{
"_id" : ObjectId("5c76e69c1e9c5dd6f1f78275"),
"InstructorId" : 200,
"InstructorName" : "Sam",
"InstructorFavouriteSubject" : [
"SQL Server",
"C#",
"Javascript"
]
}
],
"totalDocument" : [
{
"totalDocument" : 2
}
]
}