6.5830 Lecture 1 (WIP)

What is a database

collection of structured data
organized as records + relationships between them

The modern cloud data architecture

AWS Aurora (OLTP DBMS)
OLTP - online transaction processing, and typically the ones you use to build applications

Presentation Tier <-> Logic Tier <-> Client Tier

Quiz 1

Data modeling / layout
Declarative querying
- Query processing
- Algorithms for accessing and manipulating data

Why should we care?

Real world impact

Concepts

Data modeling & layout

Systematic approach to structuring / representing data
Constistency, sharing, efficiency of access to persistent data

Declarative Querying and Query Processing

Ask for data
Compiler finds optimal plan
Low-level techniques

Consistency / Transactions + Concurrency Control

Basically, ACID:

Atomicity: Operations are all-or-nothing
Consistency: Semantics are well-defined, invariants are respected
Isolation: Concurrent transactions are isolated from each other
Durability: 🤞 Hope our data doesn’t get lost

Example - Zoo

A zoo website might have:

admin interface that allows adding and editing animals
public interface for viewing pictures and maps
zookeeper interface for finding hungry animals

1k animals, 5k URLs, 10 admins, 200 keepers

Zoo Data Model

Animal entity, Cage entity, Keeper entity

What info might we want to keep about an animal? Name, species, who is the keeper, which cage is it in, etc.?

Animals have names, ages, species Keepers have names Cages have feeding times, buildings Animals are in 1 cage; cages have multiple animals Keepers keep multiple cages, cages kept by multiple keepers

Our Zoo

Mike the Moose
Tim the Giraffe
Sally the student

Operations

move all snakes to new building
- need to change many files
multiple admins editing page at the same time
- need concurrency control
system may crash mid-update
- need all-or-nothing operations
need to find animal that was fed the longest ago
- need efficient plan from database

Databases address all these issues and more

Date: August 27, 2024

Tags: lecture