Mongodb for non-relational databases (Nosql): Common Index, unique index

I. Create a new database usetoto; switchedtodbtotoshowdbs; admin (empty) local0.078GBusetoto; alias creates 1 million pieces of data for (vari1; i000000; I ++ ){... db. c3.insert ({name: zhangsan, age: I });...} db.

I. Create a new database use toto; switched to db toto show dbs; admin (empty) local0.078GB use toto; switched to db toto 2 create 1 million pieces of data for (var I = 1; I = 1000000; I ++ ){... db. c3.insert ({name: zhangsan, age: I });...} db.

I. Normal Indexes

1. Create a new database

> Use toto;

Switched to db toto

> Show dbs;

Admin (empty)

Local 0.078 GB

> Use toto;

Switched to db toto

> Db

Toto

>

2. Create 1 million data entries

> For (var I = 1; I <= 1000000; I ++ ){

... Db. c3.insert ({name: "zhangsan", age: I });

...}

> Db. c3.count ();

3 No index search

> Db. c3.find ({age: 500000}). explain ();

Create an index for the 4-digit age Field

Db. c3.ensureIndex ({age: 1 });

At this time, we can see that the server has the corresponding output

5. Search with indexes

Db. c3.find ({age: 500000}). explain ();

Ii. Unique Index

1. delete an index:

Db. c3.dropIndex ({age: 1 });

2. Create a unique index

Db. c3.ensureIndex ({age: 1 },{ unique: true });

Db. c3.find ({age: 500000}). explain ();

3. After a unique index is created on a key, the corresponding value must be unique and cannot be added.

Db. c3.insert ({name: "lisi", age: 100 });

4 show collections;

5 db. system. indexes. find ();