Capped Collection in MongoDB

Capped collections
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-> Capped collections are fixed-size circular collections that follow the insertion order to support high performance for create, read, and delete operations.

-> By circular, it means that when the fixed size allocated to the collection is exhausted, it will start deleting the oldest document in the collection without providing any explicit commands.


Creation:
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db.createCollection( "log", { capped: true, size: 100000 } )


Specify a maximum number of documents for the collection using the max field:
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db.createCollection("log", { capped : true, size : 5242880, max : 5000 } )


-> ordering of results is the same as the insertion order.

To retrieve documents in reverse insertion order - $natural parameter set to -1
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db.cappedCollection.find().sort( { $natural: -1 } )


Check if a Collection is Capped:
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db.collection.isCapped()


Convert a Collection to Capped
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db.runCommand({"convertToCapped": "mycoll", size: 100000});

-> TTL Collections are not compatible with capped collections.