No sql databases

NoSql Databases
By Ankit Dubey

Introduction
• Non Relational Databases
• Not only SQL
• Doesn't require fixed schema
• Easy to scale & avoids join
• Used for Big Data & real time web app.

Brief History of NoSQL Databases
• 1998- Carlo Strozzi use the term NoSQL for his
lightweight, open-source relational database
• 2000- Graph database Neo4j is launched
• 2004- Google BigTable is launched
• 2005- CouchDB is launched
• 2007- The research paper on Amazon Dynamo is
released
• 2008- Facebooks open sources the Cassandra project
• 2009- The term NoSQL was reintroduced

Features of NoSQL
• Non Relational
• Schema free
• Simple API
• Distributed

Types of NoSQL Databases
• Key-value Pair Based
• Column-oriented
• Graphs based
• Document-oriented

Key Value Pair Based:
1. Data is stored in
Key/value pair
2. Store data as a hash
table
3. Key=Unique,Value=JSON
,BLOB,String etc

Column Based
1. works on column
2. every column is treated
as separatly
3. values of each column
are stored contiguously

Document Oriented
1. Stores & retrieves data as
a key value pair
2. But the value is stored as
a Document

Graph Based
1. Stores entities as well as
relations between them
2. Entity=node,Relation=Ed
ges
3. Each node & edge has
unique identifier
4. Traversing is fast

The CAP Theorem
 The limitations of distributed databases can be
described in the so called the CAP theorem
 Consistency: every node always sees the same data at
any given instance (i.e., strict consistency)
 Availability: the system continues to operate, even if
nodes in a cluster crash, or some hardware or software
parts are down due to upgrades
 Partition Tolerance: the system continues to operate in
the presence of network partitions
CAP theorem: any distributed database with shared data, can have at
most two of the three desirable properties, C, A or P

The CAP Theorem (Cont’d)
 Let us assume two nodes on opposite sides of a
network partition:
 Availability + Partition Tolerance forfeit Consistency
 Consistency + Partition Tolerance entails that one side
of the partition must act as if it is unavailable, thus
forfeiting Availability
 Consistency + Availability is only possible if there is no
network partition, thereby forfeiting Partition Tolerance

Large-Scale Databases
 When companies such as Google and Amazon were
designing large-scale databases, 24/7 Availability was
a key
 A few minutes of downtime means lost revenue
 When horizontally scaling databases to 1000s of
machines, the likelihood of a node or a network failure
increases tremendously
 Therefore, in order to have strong guarantees on
Availability and Partition Tolerance, they had to
sacrifice “strict” Consistency (implied by the CAP
theorem)

Trading-Off Consistency
 Maintaining consistency should balance between the
strictness of consistency versus availability/scalability
 Good-enough consistency depends on your application

Trading-Off Consistency
 Maintaining consistency should balance between the
strictness of consistency versus availability/scalability
 Good-enough consistency depends on your application
Strict Consistency
Generally hard to implement,
and is inefficient
Loose Consistency
Easier to implement,
and is efficient

The BASE Properties
 The CAP theorem proves that it is impossible to guarantee
strict Consistency and Availability while being able to
tolerate network partitions
 This resulted in databases with relaxed ACID guarantees
 In particular, such databases apply the BASE properties:
 Basically Available: the system guarantees Availability
 Soft-State: the state of the system may change over time
 Eventual Consistency: the system will eventually
become consistent

Eventual Consistency
 A database is termed as Eventually Consistent if:
 All replicas will gradually become consistent in the
absence of updates

Eventual Consistency
 A database is termed as Eventually Consistent if:
 All replicas will gradually become consistent in the
absence of updates
Webpage-A
Event: Update
Webpage-AWebpage-A
Webpage-A
Webpage-A
Webpage-A
Webpage-A
Webpage-A
Webpage-A
Webpage-A
Webpage-A
Webpage-A
Webpage-A

Advantages of NoSql
• It can serve as the primary data source for online
applications.
• Handles big data which manages data velocity, variety,
volume, and complexity
• Excels at distributed database and multi-data center
operations
• Eliminates the need for a specific caching layer to store
data
• Offers a flexible schema design which can easily be
altered without downtime or service disruption

• Object-oriented programming which is easy to use and
flexible
• NoSQL databases don't need a dedicated high-
performance server
• Support Key Developer Languages and Platforms
• Simple to implement than using RDBMS
• No Single Point of Failure
• Easy Replication

• It provides fast performance and horizontal scalability.
• Can handle structured, semi-structured, and unstructured
data with equal effect

No sql databases

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