A Study on Mongodb Database

IJSRD - International Journal for Scientific Research & Development| Vol. 3, Issue 10, 2015 | ISSN (online): 2321-0613
All rights reserved by www.ijsrd.com 832
A Study on Mongodb Database
Kavya. S
M Tech. Student
Department of Computer Science
Mount Zion College of Engineering, A. P. J. Abdul Kalam Technological University, Kadammanitta
P.O, Pathanamthitta, Kerala, India
Abstract— This paper trying to focus on main features,
advantages and applications of non-relational database
namely Mongo DB and thus justifying why MongoDB is
more suitable than relational databases in big data
applications. The database used here for comparison with
MongoDB is MySQL. The main features of MongoDB are
flexibility, scalability, auto sharding and replication.
MongoDB is used in big data and real time web applications
since it is a leading database technology.
Key words: NoSQL, MongoDB, auto sharding, aggregation
I. INTRODUCTION
Relational database management systems came into
existence since 1980’s.They are a common choice of storage
of information in new databases used for financial records,
manufacturing and logistical information personnel data and
other applications. They work efficiently when they handle a
limited amount of data. Due to the emergence of
applications that support millions of users simultaneously an
appropriate database is required. To handle huge volume of
data traditional relational database is inefficient. To
overcome the difficulty in handling huge volume of data ,the
term NoSQL was introduced by Crlo Strozzi in 1998.It
refers to non-relational databases. More recently,the term
has received another meaning namely Not Only SQL.The
main advantage of NoSQL database is that it can handle
both unstructured(e-mail,multimedia,social media) and semi
structured data very efficiently. Mainly there are four
categories of databases namely Key –value store, document
store, column oriented and graph database. MongoDB is a
cross platform document oriented database, first developed
by the software company MongoDB Inc., in October 2007
as a component of planned platform as a service product.
The company shifted to an open source development model
in 2009.Since, then MongoDB has been adopted as a
backend software by a number of major websites and
services. These include Craigslist, eBay, Foursquare and
Newyork Times. MongoDB is written in c++ and provides
high availability, easy scalability and better performance.
MongoDB works on the concept of collection and
document. A database is a physical container for collections.
Collection is a group of MongoDB documents. It is
equivalent to RDBMS table. MongoDB database contain
multiple collections. A document is a set of key-value pairs.
Documents have dynamic schema. That means, documents
in the same collection do not need to have the same structure
and common fields. MongoDB supports dynamic queries on
documents using a document based query language that is
nearly as powerful as SQL.It stores the data in the form of
JSON documents. Auto sharding, replication and high
availability are the main features of MongoDB.It is
commonly used in big data, content management and
delivery, mobile and social infrastructure, user data
management and data hub. MongoDB supports different
data types such as String, Integer, Boolean,
Double,Min/Max keys, Arrays, Timestamp, Oject, Null,
Symbol, date, Object ID, Binary data, code and regular
expressions.
II. MONGODB DATA MODEL
MongoDB stores data as documents which are in the BSON
format. BSON is binary representation of JSON document.
Documents having similar structure are organized as
collections. Collection is analogous to a table in relational
database. Documents and fields in MongoDB are
represented using the terms row and columns respectively in
MySQL. The difference between the relational database,
MySQL and non-relational database ,MongoDB is that in
relational database information for a given record is usually
spread across many tables, whereas in MongoDB the
documents tend to have all data for a given record in a
single document.
MySQL MongoDB
Table Collection
Row BSON document
Column BSON field
JOIN Embedded documents and Linking
GROUP BY Aggregation
Primary key Primary key
Table 1:
III. FEATURES OF MONGODB
MongoDB has a flexible data model. That means data can
be stored in any structure. This feature also allows
modification of data in an easy way. Another main feature is
elastic scalability. All NoSQL databases contain some form
of sharding or partitioning.This allows the database to scale
out on hardware. Thereby allowing almost unlimited
growth. MongoDB provides high performance than
traditional relational databases. The performance of
MongoDB is measured in terms of both throughput and
latency at any scale. MongoDB does not use join operation,
instead they use embedding of documents and linking.
Because the data in MongoDB is more localized.This
localization dramatically reduces the need to join separate
tables. Each document structure in MongoDB database can
vary from one another. If there is a need to create a new
field in any one of the document, then the field can be
created without affecting a central system catalog and
without taking the system offline. In MongoDB, field
updates can be done easily. It provides rich data model. Data
locality and dynamic schema are other main features of
MongoDB. The main feature of MongoDB includes
querying, aggregation, indexing and auto sharding.
Indexes play a major role in providing efficient
access to data,for both read and write operations,which are

(IJSRD/Vol. 3/Issue 10/2015/182)
supported natively by the database rather than maintained in
application code. MongoDB supports many queries, mainly
for highly scalable operational applications. The result of
query execution can be a document or subset of specific
fields within the document.
Different types of query provided by MongoDB
include key value queries, range queries, geo spatial queries,
search queries, text search queries, aggregation framework
queries and map reduce queries. Replica sets are another
feature of MongoDB which is a fail over mechanism. Only
the primary database allows write operation. Multiple
secondary servers are used for read operation. For a replica
set, minimum three servers is required. Of the three servers,
one is primary server, other is secondary server and the
remaining one is arbiter server. Arbiter server is not used for
storing data. They are used only during failover time to
determine which server will be the next primary server.
Another feature is auto sharding. This feature is used to
overcome the hardware limitations. Hardware limitations
means bottleneck in RAM/disk I/O. This feature of
MongoDB helps to distribute data across physical partitions.
These physical partitions are called as shards. Thus data is
automatically balanced in the clusters as the data grows. In
relational database sharding is not built into the database.
An aggregate is a group of related entities and value object.
Maximum document size in MongoDB is 16 MB and large
documents are handled with Grid FS.MongoDB runs on OSs
such as Windows, Linux, Mac and Solaris.
IV. COMPARISON OF MONGODB VS MYSQL
MongoDB Commands
SELECT * FROM table db.collection.find()
SELECT * FROM table
WHERE user=’Akshay’
db.collection.find({user=”Akshay”})
SELECT * FROM table
ORDER BY Age
Db.collection.find.
DISTINCT .distinct()
GROUP .group()
Table 2: Fig (a) Retrieval of data in MySQL and MongoDB
Modeling of data in MongoDB database differs from
relational database. Different modeling styles can be applied
depending on the requirement of the application. Most
common modeling styles are embedding of documents and
normalization on collections. The embedding feature has a
disadvantage. That is, it may cause the situation that
documents grow in size after creation which may degrade
the performance of database.
Col 1
Col 2
Col 3
Table 3: Fig(b)Data modeling by embedding of documents
Example of Embedded documents having one to
one relationship is shown below.
{_id:1,Name:”Akshay Anand”,Address :{
City”:”Kochi”,Country:”India”}}
Example of Embedded documents having one to many
relationship is shown below
{_id:1,Name: “Akshay Anand”,Children
:[{Name:”Aravind”,Age:2},{Name:”Anupama”,Age:4}]
This shows that array of values can be stored easily in
MongoDB.
MongoDB supports denormalization.It is a process
of reducing number of physical tables which are accessed
more frequently to reduce the query processing time.This
process reduces number of joins required to design the query
to get desired output.
Col-1 Col-2
Table 4: Norm.
Col 1 Col 3
Table 5: Fig(c) Normalization.
Col 1 Col 2 Col 3
Table 6: Fig (d)D normalization.
In MySQL,the concept of normalization is used.
This concept was first introduced by E.F.Codd. The
objectives of normalization process include well
organization of data, minimizing update anomalies and
maximizing data accessibility. In ©,a common key is used
to refer the tables Table1_Norm and Table2_Norm.In the
next figure, the tables are merged together. Embedding is
similar to denormalizationbut still little variation is there.
Embedding of documents give better performance than
normalization on collections.
V. ADVANTAGES OF MONGODB
It is schema less. MongoDB database belongs to document
store category in which one collection holds different
different documents. Number of fields, content and size of
the document can be different in each document. The main
advantage of MongoDB database is that structure of a single
object is clear. It does not contain complex joins.It has deep
query ability. Easy of scale out is another major advantage.
In this type of database, conversion/mapping of application
objects to database objects not needed. MongoDB uses the
internal memory for storing the work set there by enabling
faster access of data. It provides index on any attribute. The
secondary indexes supported by the MongoDB database
make them transparent to developers.
VI. APPLICATIONS OF MONGODB
They are widely used in big data and real time web
applications such as Facebook, Yahoo, Google and Amazon.
It is also used in content management and delivery. It can be
used in mobile and social infrastructure. For user data

(IJSRD/Vol. 3/Issue 10/2015/182)
management the best choice among NoSQL database is
MongoDB. It finds application in data hub also.It is the best
choice for a small or medium sized non –critical sensor
applications, especially when write performance is
important.
VII. CONCLUSION
As NoSQL trend is relatively new, many researchers are
attracted to this category of databases. NoSQL databases
such as MongoDB and its key-value stores provide an
efficient framework to aggregate large volumes of data.
MongoDB can store complex data like array,object or
reference into one field. Mapping of objects is very easy in
this type of database. The features of MongoDB like auto
sharding and replication of data make the development
faster than MySQL. MongoDB provides flexibility,
horizontal scalability, auto sharding and replication.
MongoDB is a better choice for big data applications than
MySQL database. It gives better performance than relational
database. Depending on the requirements of application, we
can choose the suitable NoSQL database.
REFERENCES
[1] Mrs.Anuradha Kanade, Dr.Arpita Gopal,Mr.Shanthanu
Kanade“A Study of Normalization and Embedding in
MongoDB”Advance Computing Conference (IACC),
2014 IEEE International
[2] Cornelia GYORODI,Robert GYORODI,George
PECHERLE,Andrada OLAH “A comparative
study:MongoDB vs MySQL”Engineering of Modern
Electric Systems (EMES), 2015 13th International
Conference on11-12 June 2015.
[3] K.Sanobar,M.Vanita,”SQL Support over MongoDB
using Metadata”

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