4. Non-relational database (Nosql) MongoDB: Normal index, unique index



One: Normal index

1 to create a new database

> Use Toto;

Switched to DB Toto

> Show DBS;

Admin (empty)

Local 0.078GB

> Use Toto;

Switched to DB Toto

> DB

Toto

>

2 Create - million-piece data

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

... db.c3.insert ({name: "Zhangsan", age:i});

... }

>db.c3.count ();

3 No index lookup

>db.c3.find ({age:500000}). Explain ();

4 bit Age field to create an index

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

You can see the server side has the corresponding output

5 have index lookup

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

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Two: Unique index

1 To 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 in a Key The corresponding value must be unique after a unique index has been established on the Join not go back and forth.

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

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4 show Collections;

5 Db.system.indexes.find ();

4. Non-relational database (Nosql) MongoDB: Normal index, unique index