Serializable isolation in PostgreSQL - Mini Project: Build & Apply

Understanding Serializable Isolation in PostgreSQL

📖 Scenario: You are managing a small online bookstore database. Multiple users can place orders and update inventory at the same time. To avoid conflicts and ensure data consistency, you want to use the serializable isolation level in PostgreSQL transactions.

🎯 Goal: Build a set of SQL commands that demonstrate how to set up a table, configure the transaction isolation level to serializable, perform a transaction that updates inventory safely, and commit the transaction.

📋 What You'll Learn

Create a table named books with columns id (integer primary key), title (text), and stock (integer).

Set the transaction isolation level to serializable before starting a transaction.

Begin a transaction and update the stock of a specific book by decreasing it by 1.

Commit the transaction to save changes.

💡 Why This Matters

🌍 Real World

Online stores and banking systems use serializable isolation to prevent data conflicts when many users update data at the same time.

💼 Career

Understanding transaction isolation levels is important for database administrators and backend developers to ensure data integrity and avoid errors in multi-user environments.

1

Create the books table

Write a SQL statement to create a table called books with columns id as an integer primary key, title as text, and stock as integer.

PostgreSQL

-- Create the books table with id, title, and stock columns
-- Your code here

Need a hint?

Use CREATE TABLE with the specified columns and types.

2

Set transaction isolation level to serializable

Write a SQL statement to set the transaction isolation level to serializable before starting a transaction.

PostgreSQL

CREATE TABLE books (
    id INTEGER PRIMARY KEY,
    title TEXT,
    stock INTEGER
);

-- Set the transaction isolation level to serializable
-- Your code here

Need a hint?

Use SET TRANSACTION ISOLATION LEVEL SERIALIZABLE; to set the isolation level before starting a transaction.

3

Begin transaction and update stock

Write SQL statements to begin a transaction, then update the stock of the book with id = 1 by decreasing it by 1.

PostgreSQL

CREATE TABLE books (
    id INTEGER PRIMARY KEY,
    title TEXT,
    stock INTEGER
);

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;

-- Begin transaction and update stock of book with id 1
-- Your code here

Need a hint?

Use BEGIN; to start the transaction and UPDATE to change the stock.

4

Commit the transaction

Write a SQL statement to commit the transaction and save the changes.

PostgreSQL

CREATE TABLE books (
    id INTEGER PRIMARY KEY,
    title TEXT,
    stock INTEGER
);

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE;

BEGIN;
UPDATE books SET stock = stock - 1 WHERE id = 1;

-- Commit the transaction
-- Your code here

Need a hint?

Use COMMIT; to save the transaction changes.