Database Migration MySQL to PostgreSQL

By Kokil Thapa | Last reviewed: August 2026

Executing a database migration MySQL to PostgreSQL is rarely as simple as running a dump-and-restore command; it requires translating two fundamentally different SQL dialects while preserving data integrity in production. Whether you are moving a legacy PHP application or upgrading a modern Laravel 12 system to leverage advanced Postgres features, the friction lies in type mismatches, unsigned integers, and auto-increment sequences rather than the raw data transfer itself. For teams managing critical business systems, such as the legal-tech portals I maintain, this transition demands a structured approach that prioritizes verification over speed. If you are evaluating whether your current infrastructure can support this shift or need expert guidance on database-driven website development in Nepal, understanding these mechanical differences is the first step toward a successful migration.

Why does database migration MySQL to PostgreSQL fail silently?

Most failed migrations do not crash; they succeed partially, leaving applications running against corrupted or truncated datasets. The root cause is usually implicit type coercion. MySQL is permissive by design, allowing silent truncation of strings and overflow of integers depending on the SQL mode. PostgreSQL is strict; it rejects invalid data outright. When you perform a database migration MySQL to PostgreSQL, this strictness becomes your safety net, but only if you configure the loader to report errors correctly instead of skipping bad rows.

A specific pain point I encounter regularly involves unsigned integers. MySQL supports INT UNSIGNED (0 to 4,294,967,295), but PostgreSQL has no native unsigned type. Its standard INTEGER tops out at 2,147,483,647. If your user IDs or order numbers exceed this limit, a naive migration will either fail or wrap around to negative values, breaking foreign keys and application logic. You must explicitly map these columns to BIGINT during schema creation. Similarly, MySQL’s TINYINT(1) boolean convention maps to Postgres BOOLEAN, but legacy code checking for 1/0 instead of true/false will break unless you add an explicit cast layer or update the application ORM mappings simultaneously.

Another frequent issue is case sensitivity. MySQL table names on Linux are case-sensitive by default, while on Windows they are not. PostgreSQL folds unquoted identifiers to lowercase. If your Laravel migrations created tables like UserProfiles and your code references them inconsistently, the migration might create userprofiles while queries look for UserProfiles, causing "relation does not exist" errors. Standardizing on snake_case for all identifiers before migration prevents this class of bugs entirely.

How do you use pgloader for reliable data transfer?

For any production database migration MySQL to PostgreSQL exceeding a few gigabytes, pgloader is superior to mysqldump | psql pipelines. It streams data directly between databases, handles type casting automatically via configurable rules, and supports resumable transfers. Unlike ETL scripts, it operates at the protocol level, bypassing intermediate SQL files that consume disk space and time. On a recent eCommerce project migrating 40GB of order history, pgloader completed the transfer in under three hours where a dump-restore cycle had previously timed out after twelve.

Installing and configuring pgloader

On Ubuntu 24.04, install from the official repository to get the latest stable version rather than the outdated apt package:

sudo apt-get install -y pgloader
# Verify version supports MySQL 8.x auth plugins
pgloader --version

Create a configuration file migrate.load that explicitly defines type mappings. Do not rely solely on defaults:

LOAD DATABASE
     FROM      mysql://root:password@localhost/source_db
     INTO      pgsql://postgres:password@localhost/target_db

WITH   include no drop,
       create indexes,
       reset sequences,
       workers = 4,
       concurrency = 2

CAST   type int unsigned to bigint using integer-to-bigint,
       type tinyint(1) to boolean using tinyint-to-boolean,
       type enum to varchar(50) drop typemod

ALTER SCHEMA 'source_db' RENAME TO 'public';

The reset sequences directive is critical. Without it, Postgres sequences remain at their initial value (usually 1) after data import, causing immediate primary key violations when the application attempts to insert new records. I have seen this exact oversight take down a legal document portal during peak filing season because the next user registration tried to reuse an existing ID.

Handling MySQL 8 authentication

MySQL 8.0+ defaults to caching_sha2_password, which older pgloader builds cannot authenticate against. If you encounter connection refused errors, temporarily switch the MySQL user to legacy authentication or upgrade pgloader:

-- Run on MySQL source before migration
ALTER USER 'migration_user'@'%' IDENTIFIED WITH mysql_native_password BY 'secure_pass';
FLUSH PRIVILEGES;

Always create a dedicated read-only migration user rather than using root. This limits blast radius if credentials leak and ensures no accidental writes occur during the transfer window.

What schema changes are required for Laravel applications?

Laravel abstracts many database differences, but not all. When performing a database migration MySQL to PostgreSQL on a Laravel 12 application, you must address framework-specific assumptions baked into migrations and Eloquent models. The most common trap is the increments() method. On MySQL, this creates an unsigned auto-incrementing integer. On Postgres, it creates a signed serial. If your existing data contains IDs above 2.1 billion, you must change these to bigIncrements() in your migration files before running them against Postgres, or manually alter the column type post-import.

JSON columns also differ significantly. MySQL’s JSON type is binary with path extraction functions. PostgreSQL uses JSONB for indexed, queryable JSON. Laravel’s schema builder creates jsonb by default on Postgres, but if you are migrating an existing schema via pgloader, it may land as plain json (text-based, slower queries). Convert these explicitly:

-- Convert JSON to JSONB for indexing support
ALTER TABLE orders 
  ALTER COLUMN metadata TYPE jsonb USING metadata::jsonb;

-- Create GIN index for nested key lookups
CREATE INDEX idx_orders_metadata ON orders USING gin (metadata);

For applications using Laravel Scout or full-text search, note that MySQL’s FULLTEXT indexes do not transfer. PostgreSQL uses GIN or GiST indexes with tsvector columns. You will need to rebuild search indexes entirely and potentially adjust your Scout driver configuration to use the PostgreSQL engine. Teams building complex search interfaces often find this a good opportunity to integrate dedicated tools; resources on Laravel Meilisearch integration can complement native Postgres FTS for better relevance tuning.

Enum and set type replacements

MySQL ENUM and SET types have no direct Postgres equivalent. While you can create custom Postgres types, this locks you into vendor-specific DDL. The pragmatic approach for Laravel apps is converting enums to VARCHAR with a CHECK constraint:

ALTER TABLE documents 
  ADD CONSTRAINT chk_status CHECK (status IN ('draft', 'review', 'published'));

This preserves validation at the database level while keeping migrations portable. Update your Eloquent casts to match, and ensure any raw SQL queries referencing enum values are updated to string comparisons.

How do you verify data integrity after migration?

Never trust a migration based solely on row counts. Identical row counts can mask truncated text fields, shifted dates, or corrupted binary data. Implement a multi-layer verification strategy before cutting over production traffic.

For checksums, generate comparable hashes on both sides. On MySQL, use CONCAT_WS with null-safe handling; on Postgres, use COALESCE and ||. Sort by primary key to ensure deterministic ordering. Even a single character difference in collation or trailing whitespace will produce mismatched hashes, so normalize strings before hashing.

When should you choose PostgreSQL over MySQL for new projects?

While this guide focuses on migration mechanics, the strategic question matters equally. In my experience maintaining both stacks for Nepali businesses, PostgreSQL earns its keep when applications require complex querying, geographic data, or strict transactional guarantees beyond basic CRUD. Legal-tech platforms handling case relationships, document versioning, and compliance audit trails benefit enormously from Postgres CTEs, window functions, and advisory locks. For simpler content sites or high-read catalogs where MySQL’s replication maturity shines, the migration cost may not justify the switch.

Consider operational overhead too. PostgreSQL tuning is more nuanced; parameters like work_mem, shared_buffers, and autovacuum settings require active management as data grows. MySQL’s defaults often suffice longer for small-to-medium workloads. If your team lacks Postgres operational experience, budget time for learning or partner with someone who has managed it in production. Teams exploring broader backend modernization alongside database changes should review modern Laravel architecture best practices to align application patterns with Postgres strengths.

Database Migration MySQL to PostgreSQL: Final Checklist

A successful database migration MySQL to PostgreSQL hinges on preparation, not just execution. Before starting, inventory every column type, identify unsigned integers and enums, and prepare explicit cast rules. Use pgloader for streaming transfers with error logging enabled. Reset sequences immediately after import. Verify integrity through checksums and boundary checks, not just row counts. Deploy to staging first with read-only traffic to catch ORM incompatibilities. Only cut over production when automated tests pass against the new datastore.

If you are planning a migration and want to avoid the pitfalls described here, or need assistance architecting a system that leverages PostgreSQL effectively from day one, reach out to discuss your project requirements. Whether it is a legacy PHP monolith or a greenfield Laravel 12 application, getting the database foundation right determines long-term maintainability far more than any framework choice.