Mongodb create index

grammar ：

db.collection.createIndex(keys, options)

Key: The value is the index field that you want to create

1: Specifies that the index is created in ascending order

-1: Index is created in descending order

Example ：

db.col.createIndex({"title":1})

Create composite index ：

Set to use multiple fields to create an index （ A relational database is called a composite index ）

Example ：

>db.test.createIndex({"title":1,"description":-1})

createIndex() Receive optional parameters , The list of optional parameters is as follows ：

Parameter	Type	Description
background	Boolean	The indexing process blocks other database operations ,background You can specify backchannel mode to create indexes , That is, increase "background" Optional parameters . "background" The default value is false.
unique	Boolean	Is the index created unique . Designated as true Create unique index . The default value is false.
name	string	Name of index . If not specified ,MongoDB Generates an index name by concatenating the field name of the index and the sort order .
dropDups	Boolean	3.0+ Version obsolete . Whether to delete duplicate records when establishing a unique index , Appoint true Create unique index . The default value is  false.
sparse	Boolean	Indexes are not enabled for field data that does not exist in the document ; This parameter requires special attention , If set to true Words , Documents that do not contain corresponding fields are not queried in index fields .. The default value is  false.
expireAfterSeconds	integer	Specifies a value in seconds , complete TTL Set up , Sets the lifetime of the collection .
v	index version	The version number of the index . The default index version depends on mongod The version that runs when the index is created .
weights	document	Index weight , Values in 1 To 99,999 Between , Represents the score weight of the index relative to other index fields .
default_language	string	For text index , This parameter determines the list of stop words and the rules for the word stem and lexicon . Default to English
language_override	string	For text index , This parameter specifies the name of the field to be included in the document , The language overrides the default language, The default value is language.

Creating indexes in the background ：

By adding when the index is created background:true The option to , Let the creation work execute in the background

Example ：

db.values.createIndex({open: 1, close: 1}, {background: true})