Are Relational Databases the Only Type of Databases?

A Brief DB History

Early 1970s Many database systems Incompatible, exposing many implementation

details Then Ted Codd came along

Relational model Structured Query Language (SQL) Implementation differences became irrelevant A few major DB systems dominated the market

Then Web 2.0 & 3.0, Big Data Happen

What do you think happen? Semi-structured data happen.

•A lot of it and in many forms…

Some Facts about Web x.0 and Big Data Twitter: 255 million monthly active users and

500 million Tweets are sent per day, Facebook: over 1 billion monthly users and

faces 3 million message per 20 minute Instagram: 200 Million Monthly Active Users

and 1.6 Billion Likes and 60 Million Photos shared every day

Database Systems Landscape Nowadays

Somebody, Please, Bring Some Order to This Madness – Cont’d

Somebody, Please, Bring Some Order to This Madness – Cont’d

NoSQL Databases

Somebody, Please, Bring Some Order to This Madness

Different Interfaces Different hardware

support Different application

support Lack of Uniformity

Source: http://www.infoq.com/articles/State-of-NoSQL

Database Evolution Timeline

Additional Resources

Tutorial by C. Mohan, An In-Depth Look at Modern Database Systems

https://docs.google.com/file/d/0B7lNUaak0bK1encwYnBVUWZSWjA/edit

Key-Value Store

Implemented as an associative array, map, symbol table, or dictionary abstract data type composed of a collection of (key, value) pairs such that each possible key appears at most once in the collection.

A simple put/get interface Great properties: scalability, availability,

reliability

Key-Value Store Usage Scenarios Increasingly popular within data centers and in

P2P

Data center P2P

Dynamo

amazon.com

Voldemort

LinkedIn

Cassandra

Facebook

Vuze DHT

Vuze

uTorrent DHT

uTorrent

Row Store and Column Store

In row store data are stored in the disk tuple by tuple. Where in column store data are stored in the disk

column by column. Column-stores are more I/O efficient for read-only

queries as they read, only those attributes which are accessed by a query.

Source: Column-Oriented Database Systems, VLDB 2009. Tutorial; S. Harizopoulos, D. Abadi, P. Boncz

Row Store and Column Store

So column stores are suitable for read-mostly, read-intensive, large data repositories

Row Store Column Store

(+) Easy to add/modify a record

(+) Only need to read in relevant data

(-) Might read in unnecessary data

(-) Tuple writes require multiple accesses

Database Management Systems 3ed, R. Ramakrishnan and J. Gehrke 16

Program Flow

Ecological Network

Biological Network

Social Network

Chemical Network Web Graph

Graph Databases

Graph Databases: Query

Find all the restaurants my friends (in Facebook) like

So, What Does CS Curricula Cover?

Undergrad Database Courses Introduction to Relational Databases

Grad Database Courses Advanced Relational Databases in IS&T Principles of Data Management in CS

• Still relational DBMS. How about the rest of database system types?

Good question… Where is most of the research activity going on

nowadays? Good question again…

So, Why Do We Emphasize Relational DBs?

Jack Clark, The Register, 30 August 2013: “The tech world is turning back toward SQL, bringing to a close a possibly misspent half-decade in which startups courted developers with promises of infinite scalability and the finest imitation-Google tools available, and companies found themselves exposed to unstable data and poor guarantees.”

Google Spanner paper, October 2012: “We believe it is better to have application programmers deal with performance problems due to overuse of transactions as bottlenecks arise, rather than always coding around the lack of transactions.”

Sean Doherty in Wired, September 2013: “But don’t become unnecessarily distracted by the shiny, new-fangled, NoSQL red buttons just yet. Relational databases may not be hot or sexy but for your important data there is no substitute.”

And, The Key Reason of All

Gartner estimates RDBMS market at $26B with about 9% annual growth, whereas Market Research Media Ltd expects NoSQL market to be at $3.5B by 2018. Source: C Mohan’s tutorial

Databases make these folks happy ... End users and DBMS vendors DB application programmers

E.g., smart webmasters Database administrator (DBA)

Designs logical /physical schemas Handles security and authorization Data availability, crash recovery Database tuning as needs evolve

Must understand how a DBMS works!

Summary DBMS used to maintain, query large datasets. Benefits include recovery from system

crashes, concurrent access, quick application development, data integrity and security.

Levels of abstraction give data independence. A DBMS typically has a layered architecture. DBAs hold responsible jobs

and are well-paid! DBMS R&D is one of the broadest,

most exciting areas in CS.

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