如何在MongoDB中显示集合的索引？
为了显示集合的索引，您可以使用getIndexes()。语法如下-
db.yourCollectionName.getIndexes();
为了理解这个概念，让我们用文档创建一个集合。使用文档创建集合的查询如下-
> db.indexDemo.insertOne({"StudentName":"Larry","StudentAge":21});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f7c4f2f684a30fbdfd599")
}
> db.indexDemo.insertOne({"StudentName":"Mike","StudentAge":24});
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f7c552f684a30fbdfd59a")
}在find()method的帮助下显示集合中的所有文档。查询如下-
> db.indexDemo.insertOne({"StudentName":"Carol","StudentAge":20});以下是输出-
{
"acknowledged" : true,
"insertedId" : ObjectId("5c8f7c5e2f684a30fbdfd59b")
}
> db.indexDemo.find().pretty();
{
"_id" : ObjectId("5c8f7c4f2f684a30fbdfd599"),
"StudentName" : "Larry",
"StudentAge" : 21
}
{
"_id" : ObjectId("5c8f7c552f684a30fbdfd59a"),
"StudentName" : "Mike",
"StudentAge" : 24
}
{
"_id" : ObjectId("5c8f7c5e2f684a30fbdfd59b"),
"StudentName" : "Carol",
"StudentAge" : 20
}这是创建索引的查询-
> db.indexDemo.createIndex({"StudentName":-1,"StudentAge":-1});以下是输出：
{
"createdCollectionAutomatically" : false,
"numIndexesBefore" : 2,
"numIndexesAfter" : 3,
"ok" : 1
}这是显示集合索引的查询。集合名称是“indexDemo”-
> db.indexDemo.getIndexes();
以下是输出-
[
{
"v" : 2,
"key" : {
"_id" : 1
},
"name" : "_id_",
"ns" : "test.indexDemo"
},
{
"v" : 2,
"key" : {
"StudentName" : -1
},
"name" : "StudentName_-1",
"ns" : "test.indexDemo"
},
{
"v" : 2,
"key" : {
"StudentName" : -1,
"StudentAge" : -1
},
"name" : "StudentName_-1_StudentAge_-1",
"ns" : "test.indexDemo"
}
]