MongoDB Learning Notes < six >

Continue the learning of MongoDB

--Detailed index

--Index management

--Spatial Index

1. Create a simple index

(1) Prepare 200,000 data first

for (var i = 0;i< 200000;i++) {

Db.books.insert ("number": I, "name": i+ "book")

}

(2) Check the query performance

var start = new Date ()

Db.books.find ({"Number": 123456})

var end = new Date ();

End-start

(3) Create an index for number

Db.books.ensureIndex ({"Number":1}) Here 1 stands for Positive order, 1 for reverse

2. Places to be aware of

-index creation can affect insert performance while improving query performance

-for documents that are frequently queried for less insertions, consider using an index

-Indexing each key does not necessarily improve performance

-When doing sort work, the index can also be considered if it is a large amount of data

3. You can specify the name of the index at the same time when creating an index

Db.books.ensureIndex ({"Name": 1},{name: "BookName"})

4. Unique index

How to troubleshoot a collection books cannot insert duplicate documents

Create a unique index: Db.books.ensureIndex ({"Name": 1},{unique:true})

5. Remove duplicate values

What if you already have duplicate documents before creating a unique index?

Db.books.ensureIndex ({"Name": 1},{unique:true,dropdups:true})

6.hint

How to force a query to use the specified index

Db.books.find ({"Name": "Obook"}). Hint ({"name": 1})

The specified index must be a well-created index

7.explain

How to see in detail which index to use for this query and the status information for querying data

Db.books.find ({"Name": "0book"}). Explain ()

8. The creation process of the index is performed in the background

Db.books.ensureIndex ({"Name": "0book"},{bookground:true})

9. Deleting an index

Db.runcommand ({dropindexes: "Books", Index: "Name_1"}) exact deletion

Db.runcommand ({dropindexes: "Books", Index: "*"}) all deleted

MongoDB Learning Notes < six >