Step-by-Step Migration Process

1. Database Schema Analysis

Begin by analyzing the MySQL database schema to understand its structure, including tables, columns, data types, constraints, and indexes. This analysis will help in mapping MySQL objects to their equivalent PostgreSQL counterparts.

2. Schema Conversion

Use a schema conversion tool like pgloader or AWS Schema Conversion Tool (SCT) to convert the MySQL schema definitions to PostgreSQL-compatible syntax. Address any syntax differences, data type conversions, and constraints unique to PostgreSQL during this process.

Example: Converting a MySQL Table to PostgreSQL

-- MySQL Table Definition
CREATE TABLE users (
    id INT AUTO_INCREMENT PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) UNIQUE
);

-- PostgreSQL Table Definition
CREATE TABLE users (
    id SERIAL PRIMARY KEY,
    username VARCHAR(50) NOT NULL,
    email VARCHAR(100) UNIQUE
);

3. Data Migration

Export data from MySQL using tools like mysqldump or a data migration tool. Import this data into PostgreSQL using the pg_restore command or a similar tool. Pay attention to data type compatibility, character encoding, and any potential data transformation required during migration.

Example: Export and Import Data

# Export MySQL data
mysqldump -u username -p dbname > data.sql

# Import data into PostgreSQL
pg_restore -U username -d dbname data.dump

4. Convert Stored Procedures and Functions

Convert MySQL stored procedures and functions to PostgreSQL-compatible syntax manually or using automated conversion tools. Consider syntax differences, data type compatibility, and procedural logic when migrating procedural code.

Example: Converting MySQL Function to PostgreSQL

-- MySQL Function
DELIMITER //
CREATE FUNCTION get_user(user_id INT) RETURNS VARCHAR(100)
BEGIN
    DECLARE user_name VARCHAR(100);
    SELECT username INTO user_name FROM users WHERE id = user_id;
    RETURN user_name;
END //
DELIMITER ;

-- PostgreSQL Function
CREATE FUNCTION get_user(user_id INT) RETURNS VARCHAR(100) AS $$
BEGIN
    RETURN (SELECT username FROM users WHERE id = user_id);
END;
$$ LANGUAGE plpgsql;

Migrating from one database management system to another can be a daunting task, but with careful planning and execution, it can be a smooth process. In this guide, we’ll walk through the steps involved in migrating from MySQL to PostgreSQL, covering key concepts, tools, and best practices.