Database migration from MySQL to PostgreSQL can be a complex but rewarding task for organizations and developers seeking the advanced features and benefits that PostgreSQL offers. While MySQL is a widely used relational database management system (RDBMS) known for its simplicity and speed, PostgreSQL has gained popularity due to its advanced features, such as better support for complex queries, data integrity, and scalability.

This guide will walk you through the steps required to migrate MySQL to PostgreSQL, as well as some tools that can assist with the process.

Why Migrate from MySQL to PostgreSQL?

There are several reasons why someone may decide to migrate MySQL to PostgreSQL:

  1. Advanced SQL Compliance: PostgreSQL adheres more closely to SQL standards and supports more advanced features such as full-text search, JSONB, and window functions.
  2. Better Performance with Complex Queries: PostgreSQL is often favored for complex queries and larger data sets. It supports full ACID compliance and sophisticated indexing methods, making it suitable for high-performance applications.
  3. PostgreSQL’s Extensibility: PostgreSQL supports custom extensions, allowing users to extend its functionality beyond its default offerings.
  4. Data Integrity: PostgreSQL has better support for data integrity and consistency, which can be crucial for applications that require high levels of reliability.
  5. Community and Ecosystem: PostgreSQL has a vibrant and active community, providing strong documentation and support. It is also backed by various cloud services and has better compatibility with modern development frameworks.

Pre-Migration Considerations

Before migrate MySQL to PostgreSQL, it’s important to assess the source database and ensure the migration will meet your needs. Consider the following points:

  • Size of the Database: The size of your MySQL database will impact how you approach the migration. Large databases may require more careful planning to minimize downtime and ensure a smooth transition.
  • Version Compatibility: Ensure that the PostgreSQL version you intend to migrate to supports all the features of MySQL that you’re currently using.
  • Application Impact: If your application is using MySQL-specific features like MySQL-specific functions or syntax, you may need to adjust queries or database logic during the migration.
  • Data Types: MySQL and PostgreSQL support different data types, so data type conversion will need to be handled carefully to avoid data loss or corruption. For example, MySQL uses TINYINT, while PostgreSQL uses SMALLINT. The mapping between the two systems must be accounted for in the migration.
  • Testing: A thorough testing process is crucial to ensure that the migration is successful and that no data is lost or corrupted. It’s a good idea to test the migration process in a staging environment before performing it in production.

Steps to Migrate MySQL to PostgreSQL

Step 1: Backup Your MySQL Database

Before you start the migration process, make sure you create a backup of your MySQL database. This will serve as a safety net in case anything goes wrong during the migration process.

mysqldump -u root -p –all-databases >mysql_backup.sql

This will create a backup file called mysql_backup.sql. It’s essential to validate the backup by restoring it in a separate MySQL instance before proceeding with migration.

Step 2: Set Up PostgreSQL

If you don’t already have PostgreSQL installed, you will need to install and configure it on your server. This includes setting up the PostgreSQL service and configuring user permissions.

  1. Install PostgreSQL: On a Linux-based system like Ubuntu, you can install PostgreSQL using the following commands:
  2. sudoaptupdate
  3. sudo apt install postgresqlpostgresql-contrib
  4. Create a Database: Create a new database in PostgreSQL where the MySQL data will be migrated:
  5. sudo -u postgrescreatedbnew_db_name
  6. Create a User: Create a PostgreSQL user and assign it appropriate privileges:
  7. sudo -u postgrescreateuser –interactive

Assign the user to the database:

sudo -u postgrespsql

ALTER ROLE username WITH LOGIN;

Step 3: Convert MySQL Schema to PostgreSQL

One of the most challenging aspects of MySQL to PostgreSQL migrationis converting the schema. MySQL and PostgreSQL have differences in terms of data types, indexes, and constraints. The schema must be adjusted to account for these differences.

Manually Converting Schema

You can manually convert the schema by inspecting your MySQL schema and making the necessary adjustments. Herearesomeofthekeyareas to consider:

  1. Data Types: Ensure that MySQL data types are converted to the appropriate PostgreSQL data types. Forexample:
    • TINYINT in MySQL becomes SMALLINT in PostgreSQL.
    • DATETIME in MySQL becomes TIMESTAMP in PostgreSQL.
  2. Auto-Increment Columns: MySQL uses the AUTO_INCREMENT keyword to create auto-incrementing primary keys. In PostgreSQL, the equivalent is the SERIAL data type or using the BIGSERIAL data type for larger sequences.
  3. Foreign Keys: Ensure foreign key constraints are properly handled, as PostgreSQL supports foreign keys with greater enforcement.
  4. Indexes and Constraints: Verify that all necessary indexes and constraints are created in PostgreSQL to optimize performance.

Alternatively, there are tools that can assist with the automatic conversion of the schema.

Step 4: Migrate Data from MySQL to PostgreSQL

Once your schema is ready, you can start migrating data from MySQL to PostgreSQL. There are several ways to migrate the data, including using third-party tools or custom scripts.

Option 1: Use pgloader

pgloader is a powerful open-source migrationtool designed. Specifically to migrate data from MySQL (and other databases) to PostgreSQL. It automates the conversion of the schema, data types, and indexes, making the process significantly easier.

Here’s a basic example of how to use pgloader:

  1. Installpgloader:
  2. sudoaptinstallpgloader
  3. Runpgloader:

Create a configuration file to define your MySQL and PostgreSQL connections, then run the following command:

pgloader mysql://username:password@localhost/mysql_db_name postgresql://username:password@localhost/postgres_db_name

pgloader will handle the data transfer, including converting the schema and mapping data types between MySQL and PostgreSQL’s.

Option 2: Use MySQL-to-PostgreSQL

There are other commercial tools like MySQL-to-PostgreSQL, which can automate the data migration through easy-to-use graphical interface. MySQL-to-PostgreSQL’s provides all necessary features for smooth and safe migration:

  • Support all modern versions of MySQL and PostgreSQL including forks and cloud variations
  • The tool supports major database entries such as tables, data, indexes, constraints and views
  • Deep customization of the migration through numerous conversion settings
  • Option to edit table being migrated (change name, type, default values for every column)
  • Merge or synchronize existing Postgres database with MySQL data
  • Option to export MySQL data into SQL script containing Postgres to create objects and load the data (for those cases when connection to the target database is not available)

Step 5: Validate Data Integrity

Once the data has been migrated, it’s critical to verify that everything has been transferred correctly. Compare row counts, verify data accuracy, and ensure that all the indexes, foreign keys, and relationships are intact.

You can use simple queries like:

SELECT COUNT(*) FROM table_name;

Compare these counts between the MySQL and PostgreSQL’s databases to make sure the data is complete.

Step 6: Modify Application Code

Post-migration, you will likely need to adjust your application code to account for any differences between MySQL and PostgreSQL’s. Someaspects to considerinclude:

  • SQL Syntax Differences: Some SQL queries that work in MySQL’s may not be compatible with PostgreSQL. For example, MySQL has some proprietary functions or syntax (such as LIMIT vs. FETCH FIRST), which will need to be updated.
  • Connection Strings: Update your application’s database connection string to point to the new PostgreSQL database.
  • ORM Adjustments: If you’re using an ORM (like Django, Sequelize, or Hibernate), ensure that it is configured to work. With PostgreSQL and make any necessary adjustments in the ORM’s settings.

Step 7: Perform Final Testing

Finally, you should perform thorough testing to ensure that your application functions correctly with the PostgreSQL database. Test edge cases, query performance, and all aspects of data integrity.

MySQL to PostgreSQL
MySQL to PostgreSQL

Read: SQL Server Error 18456: How to Fix It

ToolsforMigration

There are multiple free open-source and commercial tools to migrate MySQL to PostgreSQL’s, providing different scope of automation and features:

  • pgloader: As mentioned, pgloader is a powerful open-source tool designed for migrating databases to PostgreSQL, including support for MySQL.
  • MySQL Workbench: MySQL Workbench has built-in tools for migrating data to other databases, including PostgreSQL, using its migration wizard.
  • AWS Database Migration Service (DMS): AWS DMS is a managed service from Amazon that can migrate databases, including MySQL to PostgreSQL, with minimal downtime.
  • MySQL-to-PostgreSQL is a commercial solution that provides an intuitivewizard-style GUI interface for database migrations, including from MySQL to PostgreSQL’s.

Conclusion

This is a strategic decision to migrate MySQL to PostgreSQL that can provide numerous benefits, such as improved performance, data integrity, and the ability to leverage PostgreSQL’s advanced features. While the migration process involves multiple steps, such as backing up the database, converting the schema, migrating data, and updating application code, there are various tools available to streamline the process and ensure a smooth transition. Whether you choose to use pgloader, AWS DMS, or other tools. The migration process can be accomplished with careful planning, testing, and validation.

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