Siksha Sarovar

Siksha Sarovar (sikshasarovar.com) is a free educational web application that helps students in India learn programming and prepare for academic and competitive exams. The platform offers structured coding courses (C, C++, Python, Java, HTML, CSS, PHP, Power BI, AI, Machine Learning, Data Science), complete university curriculum notes for BCA/MCA students with previous year question papers, Class 10 and Class 12 CBSE/HBSE school notes, and dedicated preparation material for SSC, UPSC, Banking, Railway and other government exams. Browsing the site is completely free and requires no account. Users may optionally sign in with Google solely to save their learning progress, quiz scores and personal preferences across devices.

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Siksha Sarovar is a free e-learning platform for coding courses, BCA university notes and competitive exam preparation. Optional Google sign-in saves your learning progress across devices.

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2.1 Introduction to NoSQL & Aggregate Data Models

Lesson 10 of 36 in the free Big Data-1 notes on Siksha Sarovar, written by Rohit Jangra.

2.1.1 The Rise of NoSQL

For decades, Relational Database Management Systems (RDBMS) like MySQL and Oracle were the only choice for data storage. However, the Big Data explosion exposed their limitations in Scalability and Flexibility. NoSQL (Not Only SQL) emerged as a solution.

Why NoSQL?

  1. Impedance Mismatch: The gap between the object-oriented models used in code and the relational (table) models used in databases.
  2. Scalability: RDBMS are designed for "Scaling Up" (bigger servers), which is expensive. NoSQL is designed for "Scaling Out" (clusters of small servers).
  3. Dynamic Schemas: Changing a table structure in a giant RDBMS requires downtime. NoSQL allows adding fields on the fly.

2.1.2 The Aggregate Data Model

In traditional RDBMS, data is "Normalized"—split across many tables to avoid redundancy. This makes sense for storage but requires complex "Joins" to retrieve full information.

Aggregates take the opposite approach. An aggregate is a collection of related objects that we wish to treat as a unit.

FeatureRelational (Normalized)NoSQL (Aggregate-Oriented)
LogicData is atomic (single facts).Data is naturally grouped.
JoinsNecessary and expensive.Minimized; data is pre-joined.
TransactionsACID across many tables.Usually atomic within a single aggregate.
ExampleCustomer, Order, and Item tables.A single Order Document containing customer and item info.

Benefits of Aggregates:

  • Easier Distribution: It's easy to store an entire aggregate on a single server, making sharding much simpler.
  • Performance: One disk read can often retrieve the entire unit of interest.