MongoDB Set index and ID

Ensureindex () method

To create an index, you need to use the Ensureindex () method of MongoDB.

Grammar:

The basic syntax for the Ensureindex () method is as follows yiibai.com

>db.  Collection_name.  Ensureindex({KEY:1          

The key here is to create an index in which 1 is the field name in ascending order. To create a descending index, you need to use-1.

Example

>db.  MyCol.  Ensureindex({"title":1})           

In the Ensureindex () method, you can create an index on multiple fields by multiple fields.

>db.  MyCol.  Ensureindex({"title":1,"description":-1})    

The Ensureindex () method can also accept a list of options (optional), with the list given below:

Example: DB. Custmessage.ensureindex ({"Custno": 1},{unique:true})

Parameters	type	Description
Background	Boolean	Indexing is established in the background so that indexing does not prevent other database activities. Specifies true to establish in the background. The default value is False.
Unique	Boolean	Create a unique index so that the collection does not accept the Insert index key or the key that matches the existing value stored in the index document. Specifies to create a unique index. The default value is False.
Name	String	The name of the index. If not specified, MongoDB generates an index name for the index field and the sort order concatenation.
Dropdups	Boolean	Create a unique indexed field that may have duplicates. MongoDB index only the first occurrence of a key, all files removed from the collection contain subsequent occurrences of that key. Specifies to create a unique index. The default value is False.
Sparse	Boolean	If true, the reference refers only to the field specified by the document. These indexes use less space, but in some cases, in particular, a variety of different manifestations. The default value is False.
Expireafterseconds	Integer	Specifies a value in seconds for the TTL control for how long the MongoDB document remains in this collection.
V	Index version	The index version number. The default index version depends on the version of MongoDB run when the index is created.
Weights	Document	Weights are numbers from 1 to 99999, representing the meaning of the field, relative to the other index field fractions.
Default_language	String	For text indexing, decide which language to stop the word and stemmers and the list of markup generation rules. The default value is 中文版.
Language_override	String	For text indexes, the specified name is included in the document that overrides the default language in the Language field. The default value is language.

MongoDB Set index and ID