Create capped collections

Capped collections: is a fixed-size collection.

It has high performance and queue expiration characteristics (expiration in order of insertion). Somewhat similar to the concept of "RRD".

The Capped collections is a high-performance automatic maintenance object Insertion Order. It is very suitable for similar logging functions and the standard collection differs, you must explicitly create a capped collection, specifying the size of a collection, in bytes. Collection data storage space values are allocated in advance. Note that the specified storage size contains the header information for the database.

If you create a normal collection:
> db.createcollection ("Mycollection01")

To create a capped collection:
> db.createcollection ("Mycoll", {capped:true, size:100000})

In capped collection, you can add new objects. Can be updated, however, objects do not increase storage space. If it increases, the update will fail. The database is not allowed to be deleted. Use the drop () method to delete all collection rows. Note: After deletion, you must explicitly recreate this collection. In a 32bit machine, the capped collection has a maximum storage of 1 billion bytes.

Create capped collections