indexes

Indexes:

createIndex -> db.collection.createIndex({a:1})

getIndex-> db.collection.getIndex(

dropIndex


1)default index

2)Unique:true

db.collection.ensureIndex(key#,<options>)}

eg:

db.foo.ensureIndex({empid:1},{unique:true})

3) sparse:true 

db.foo.ensureIndex({empid:1},{Special:true})

4)TTL - Time to live
db.eventlog.createIndex("lastModifiedDate":1},{expireAfterSeconds:3600})

5) Geo Spatial and 2d Indexes

db.places.ensureIndex({location:"2dsphere"})

- 2dsphere to mention the "Latitude & Longitude"

db.places.ensureIndex({location:"2d"})

- 2d refers x & y axis


Spatial query

db.places.find({loc:
{$near:{$geometry:
{type:"point", coordinates:[2,2,01]},
spherical:true
}
}
  }
)

--$near -> spatial operator
--$geometry:{type:"point", coordinates:[2,2,01]} -> parameters

6) Text indexes

db.sentences.ensureIndex({words:"text"})  - CREATING TEXT INDEX ON COLUMN WORDS

db.sentences.find({$text:{$search:"cat"}})

db.movies.find( { $text : {$search : "Big Lebowski" } } ) - it gives output of strings maches with "Big" or Lebowski" or both.

db.sentences.find({$text:{search:"Trees cat"}),{score:{$meta:"textScore"},_id:0}) - It gives search match ranking, _id:0 is for display subpression


db.sentences.ensureIndex({words:"text"},{default_language:"english"}) - text index language selection


******************NOTE**************************


Index can be created at the background so that read and write on the collection will not be impacted

- db.collection.createIndex({a:1}) => db.collection.createIndex({a:1},{background:true})

-However, background is applicable only for "primary" and secondary still uses foreground option

-Background uses RANDOM I/O, it takes extra time

-It will not return to prompt until background process is completed