CE419 Session 26: NoSQL Databases Web Programming The Relational - - PowerPoint PPT Presentation

CE419 Web Programming

Session 26: NoSQL Databases

The Relational Model

• Relational database management systems require

defined and clearly set schemas.

• Use SQL to query for data.
• Despite their strict nature of forming and handling data,

relational databases can become extremely flexible and

• ffer a lot, granted with a little bit of effort.

NoSQL

• A NoSQL database provides a

mechanism for storage and retrieval of data that is modeled in means other than the tabular relations used in relational databases.

• NoSQL database systems do

not come with a model as used (or needed) with structured relational solutions.

• NoSQL databases do not have

a common way to query the data and each solution provides its own query system.

SQL vs. NoSQL

• Structure and type of data being kept
• Querying
• Scaling
• Reliability
• Support
• Complex data keeping and querying needs

NoSQL (cont'd)

• Types
• Key-Value stores
• Graph
• Column-oriented
• Document
• Multi-model

Key-Value Stores

• A key-value store, or key-value database, is a computer

program designed for storing, retrieving, and managing associative arrays (dictionaries).

• Redis: SHOWTIME.
• Example usages?

Graph Databases

• A graph database is a database that uses graph

structures for semantic queries with nodes, edges and properties to represent and store data.

• Examples:
• Neo4j
• FlockDB

Column-oriented Databases

SNO STATUS CITY SNAME

• -- ------ ---- -----

S1 20 London Smith S2 10 Paris Jones S3 30 Paris Blake S4 20 London Clark S5 30 Athens Adams S120LondonSmith;S210Paris Jones;S330ParisBlake;S420 LondonClark;S530AthensAda ms S1S2S3S4S5;2010302030;Lon donParisParisLondonAthens ;SmithJonesBlakeClarkAdam s

Column-oriented Databases (cont'd)

Document Databases

• Sometimes data is not easy to describe with relational

databases.

• Example: a product search engine.

{ name: "Peugeot 206", price: 36000000, hp: 105, top_speed: 180, gearbox: "manual", color: "White" } { name: "Seagate HDD", price: 210000, capacity: "500GB", rpm: 7200, ports: ["SATA", "USB"], color: "Red" }

Document Databases (cont'd)

• Documents may be addressed in the database via a

unique key that represents that document.

• Auto-increment integer?
• UUID, ObjectId

UUID

• Universally Unique Identifier
• A UUID is simply a 128-bit value. The meaning of each bit

is defined by any of several variants.

• Human readable display
• The intent of UUIDs is to enable distributed systems to

uniquely identify information without significant central coordination.

de305d54-75b4-431b-adb2-eb6b9e546014

UUID Variants

• Version 1 (MAC Address & date-time)
• Single point in time & space
• Version 4 (Random)
• udid library in Python.

MongoDB

• MongoDB is the most popular NoSQL, document based,

database system.

• MongoDB can still hold various databases of different

names within one installation package.

• But inside databases are collections, not tables.
• A collection may be considered a table except there

are no aligned columns.

What does it mean?

• Consider a collection of users.
• Now each of these entries or rows inside a collection is

called a document.

• They are basically JSON data blocks.

Querying MongoDB

• mongo command opens MongoDB shell.
• It's a JavaScript shell!

Querying MongoDB (cont'd)

• db.collection.find()
• db.collection.insert()
• db.collection.update()
• etc…
• Let's see something in action!

CAP Theorem

• CAP theorem states that there are three basic

requirements which exist in a special relation when designing applications for a distributed architecture:

• Consistency, Availability, Partition Tolerance