MONGODB Basic Operations Data Creation Index

When the amount of data is low, the query is fast, but when the data is large, the query becomes very slow, in MongoDB

View Index

>  db.test_collection.getIndexes ()[    {        "V": 2,        "key" : {            "_id": 1         },        " Name ":" _id_ ",        " ns ":" Config.test_collection "    }]

Get indexed only _id

Create an index

> Db.test_collection.ensureIndex ({x:1}){    false,    " Numindexesbefore ": 1,    " Numindexesafter ": 2,    " OK ": 1}

If the number of documents, create an index, it takes a certain amount of time, if the system load is heavy, and there are many existing documents, you can not directly use this command to create, you need to use the database before the index is created, otherwise severely affect the database performance,

MONGODB Basic Operations Data Creation Index