MongoDB can be used as a file system, taking advantage of load balancing and data replication features over multiple machines for storing files.
In this article we will learn about storing data in Mongo. Mongo
is a document database and a document can be structured pretty much anyway we want.
Mongo imposes no schema restrictions and does not demand that we declare a
Previous articles have provided an introduction to mongo dB and
the set up and installation, and few command line options.You can get them from
The objective of the article is to learn about Storing data in
We gonna take a look at storage engine, saving documents and updating
The storage engine overview will help us understand the internals of how mongo lays
out the information.
Saving documents and Updating documents will focus on the commands
in order to save our documents.
First let us talk about how data is stored by the engine…Now if
our application wants to interact with some information that information is a
memory in our application…It can talk to the server and the server has preeminence
storage named in the disk….
The Question is how does the engine store the data??
Mongo uses Memory mapped Files the server cannot store all its
information in memory.But it would like to think of information has just existing in being available to it at any given moment..so what it does is it creates a Mongo server and maps it using memory mapped files whenever it calls it into play a portion of that array the operating system takes care of loading it or saving it to the disk..When we wanna store a bit of information we handle it over the server,and the server scribbles it over a memory and that memory gets manged and serialized to disk.. The same process in reverse happens when we want to read data the server will attempt to access a portion of the large byte array which will be loaded as needed from the operating system..
so now byte arrays can be stored on disk...now the question arises here..how does our document which doesn't have schema that get saved and what format does it get saved??
The answer is BSON...The BSON specifications can be found on http://bsonspec.org/
The BSON data format has several advantages some key advantages are that there is very little marshaling necessary from BSON elementary datatypes into c datatypes that makes reading and writing very fast in any of the programming languages.we can learn more at http://bsonspec.org/.
Rules for saving data
Rule 1: A document must have an ID field.._id Every document in mongo must have an Id if we save one without an Id mongo will assign an id field,But every document we save must have an ID..
Rule 2: The size of the document in Mongo is currently limited to 16 Mega Bytes..if we need to store more than that
we will have to store across multiple documents.This is something that may evolve in future releases.But this is the current limitation...
In this article we have learn about storage internals in mongo db and about BSON..In coming articles we will see the practical example.