MongoDB

Unique index

To prevent duplicated records when inserting new document into MongoDB collection with:

> db.neki_collection.insert({'var':'val'})

 

create unique index:

> db.neki_collection.createIndex({"page_url": 1}, {unique: true})

> db.content.createIndex({pageURL:1},{name:"pageURL", unique:true})

 

drop the index

>db.neki_collection.dropIndex({"page_url": 1})    - drop by index definition

>db.content.dropIndex("pageURL")    - drop by index name                

 

create index and name it:

>db.neki_collection.createIndex({"cid": -1, "title": 1}, {name: "myIndex"})

- cid has descending order (from greater to smaller value)

- title is ordered ascending (from smaller to greater, or from A to Z)

- index is named with "myIndex"

 

 

 

In the above example unique index is created for page_url field.

To check indexes use:

> db.neki_collection.getIndexes()

[
    {
        "v" : 1,
        "name" : "_id_",
        "key" : {
            "_id" : 1
        },
        "ns" : "crawler.ads"
    },
    {
        "v" : 1,
        "name" : "page_url_1",
        "key" : {
            "page_url" : 1
        },
        "unique" : true,
        "ns" : "crawler.ads"
    }
]