MySQL has been a reliable database platform for countless applications, but many UK businesses are now evaluating PostgreSQL for new development, modernization, cloud migration, scalability, and broader open-source database capabilities.
Moving from MySQL to PostgreSQL, however, is not simply a matter of exporting data from one database and importing it into another. The two platforms differ in SQL behavior, data types, indexing, functions, procedures, transaction handling, and operational tooling.
A successful migration therefore requires more than a database-copying tool. It requires assessment, schema conversion, data migration, application compatibility testing, validation, security planning, and a carefully managed cutover.
This guide explains the major considerations for UK businesses evaluating MySQL-to-PostgreSQL migration services.
Why Migrate from MySQL to PostgreSQL?
The business case for migration varies from organization to organization.
Common drivers include:
- Modernizing legacy applications
- Standardizing on PostgreSQL across projects
- Moving to cloud-managed PostgreSQL
- Reducing dependence on a particular database ecosystem
- Supporting more complex data models
- Improving application capabilities through PostgreSQL features
- Consolidating database platforms
- Preparing applications for future modernization
PostgreSQL supports a broad range of advanced relational capabilities and is available across major cloud platforms and managed database services.
However, migration should begin with the business and technical objective, not simply the assumption that PostgreSQL is automatically the better choice.
Ask:
What problem are we trying to solve by migrating?
If the objective is cloud modernization, cost optimization, application modernization, or database standardization, that objective should drive the migration architecture and success criteria.
MySQL to PostgreSQL Migration: What Actually Changes?
The most important point is that this is a heterogeneous database migration.
The source and target databases use different database engines, so schema and application compatibility must be evaluated.
Potential migration areas include:
- Tables and columns
- Primary and foreign keys
- Indexes
- Constraints
- Views
- Stored procedures
- Functions
- Triggers
- Auto-increment behavior
- Data types
- Character sets and collations
- SQL queries
- Application ORM mappings
- Database permissions
For example, MySQL's AUTO_INCREMENT behavior does not map directly to PostgreSQL in exactly the same way. PostgreSQL commonly uses identity columns or sequences.
Likewise, SQL syntax, functions, date handling, Boolean behavior, JSON functionality, and stored-program implementations may require changes.
This is why schema conversion and application compatibility are often more important than the physical data transfer itself.
A Practical MySQL to PostgreSQL Migration Process
A structured migration typically follows these stages.
1. Discovery and Assessment
Start by profiling the existing MySQL environment.
Review:
- Database size
- Number of tables
- Largest tables
- Indexes
- Foreign keys
- Views
- Stored procedures
- Triggers
- Functions
- Scheduled jobs
- Application dependencies
- Database versions
- Character sets
- Collations
- Replication
- Backup and recovery processes
The assessment should also identify objects that cannot be transferred directly and require manual conversion.
2. Schema Conversion
The next step is converting the MySQL schema into PostgreSQL-compatible definitions.
This can involve:
- Data-type mapping
- Primary-key conversion
- Identity/sequence configuration
- Index conversion
- Constraint conversion
- View conversion
- Trigger conversion
- Function conversion
- Stored procedure rewriting
Automated schema-conversion tools can accelerate this stage, but complex database logic should still be reviewed by experienced engineers.
AWS DMS Schema Conversion, for example, supports MySQL as a source and PostgreSQL as a target for converting database code objects.
3. Data Migration
Once the target schema is ready, the actual data can be transferred.
The appropriate method depends on the migration requirements.
Full-load migration
All required data is copied from MySQL to PostgreSQL.
This approach can work well when:
- The database is relatively small.
- Downtime is acceptable.
- The application can be stopped during migration.
Full load + Change Data Capture
For larger or business-critical systems, organizations may want to copy the existing data while continuing to capture changes made to the source.
This allows the target PostgreSQL database to catch up before the final cutover.
AWS Database Migration Service supports heterogeneous migrations and provides migration workflows for moving between different database platforms.
The exact CDC architecture depends on the MySQL environment, version, replication configuration, and target platform.
MySQL to PostgreSQL Migration Tools
There is no single migration tool that is ideal for every project.
AWS Database Migration Service
AWS DMS is useful when organizations need managed migration capabilities, particularly for cloud migration scenarios and environments requiring ongoing replication.
AWS provides migration workflows covering MySQL and PostgreSQL among other database platforms.
AWS DMS Schema Conversion
This can help convert database schema and code objects from MySQL to PostgreSQL.
pgloader
pgloader is an open-source migration tool frequently used for database migrations and can automate many aspects of data loading and transformation.
It can be useful when teams want greater control over the migration environment and command-line workflow.
Native export/import tools
For some migration scenarios, teams may use MySQL-native export mechanisms combined with transformation scripts and PostgreSQL loading tools.
This can provide control but may require more engineering effort for heterogeneous migrations.
Custom migration scripts
Custom scripts become useful when the source database contains unusual data transformations, legacy structures, business-specific conversions, or objects that automated tools cannot translate correctly.
In practice, larger migrations often use multiple tools rather than relying on one tool for everything.
How Much Does MySQL to PostgreSQL Migration Cost in the UK?
Migration costs vary considerably, so quoting a fixed price without assessing the database would be misleading.
The major cost drivers include:
Database size
A database containing a few gigabytes is fundamentally different from one containing several terabytes.
Application complexity
A simple CRUD application may require limited changes. An enterprise application with hundreds of queries, procedures, integrations, and background jobs can require substantial application remediation.
Database logic
Stored procedures, triggers, functions, and complex SQL can increase conversion effort.
Downtime requirements
If several hours of downtime are acceptable, a simpler migration approach may be possible.
If the business requires near-continuous availability, CDC and controlled cutover strategies may be required.
Testing requirements
Production migrations require more than checking whether row counts match.
Teams may need:
- Functional testing
- Data reconciliation
- Query-performance testing
- Integration testing
- Regression testing
- Security testing
- User acceptance testing
Cloud infrastructure
Moving to Amazon RDS, Aurora PostgreSQL, Azure Database for PostgreSQL, Google Cloud SQL, or another managed environment introduces infrastructure and operational costs.
Therefore, UK businesses should evaluate total migration cost, not simply the fee charged by a migration provider.
A Practical Migration Cost Model
A useful planning model is:
Migration Cost = Assessment + Schema Conversion + Data Migration + Application Remediation + Testing + Infrastructure + Cutover + Post-Migration Support
For a more realistic business case, also consider the cost of:
- Application downtime
- Engineering resources
- Performance issues
- Failed migration attempts
- Temporary infrastructure
- Data-quality remediation
- Rollback preparation
This is why a proper discovery phase is valuable before requesting a final migration quote.
Delivery Models for UK Businesses
Organizations generally have several options.
In-house migration
Suitable when the organization already has strong database, application, DevOps, and cloud expertise.
Specialist migration partner
Useful when the migration is complex or business-critical and the organization wants dedicated migration expertise.
Hybrid delivery
Internal teams retain application ownership while an external migration team handles database assessment, tooling, CDC, testing, and cutover support.
For many organizations, the hybrid model can provide a practical balance between internal knowledge and specialist migration experience.
How to Minimize Downtime
Downtime requirements should be defined at the beginning of the project.
A common low-downtime strategy is:
Assess → Convert Schema → Initial Load → Replicate Changes → Validate → Freeze Writes → Final Sync → Cut Over → Monitor
The migration team can continue synchronizing changes while the source application remains operational.
During the final cutover window, writes are paused, the remaining changes are synchronized, validation is completed, and application connections are switched to PostgreSQL.
The exact approach depends on the source architecture and CDC capabilities.
Data Validation: The Step You Should Not Skip
A migration is not successful simply because PostgreSQL contains the expected tables.
Validation should cover multiple levels.
Structural validation
Check:
- Tables
- Columns
- Constraints
- Indexes
- Views
- Functions
- Triggers
Data validation
Compare:
- Row counts
- Checksums where appropriate
- Aggregates
- Null values
- Key relationships
- Sample records
Application validation
Test:
- Login
- Transactions
- Reports
- Search
- APIs
- Background jobs
- Integrations
- Business workflows
Performance validation
Compare important queries and application workflows against agreed performance expectations.
Common MySQL to PostgreSQL Migration Challenges
SQL incompatibilities
Queries written specifically for MySQL may require modification.
Stored procedures
MySQL stored-program logic may require rewriting for PostgreSQL.
Data-type differences
Some MySQL types and behaviors require explicit mapping.
Collation differences
Sorting and comparison behavior can change after migration.
Application dependencies
ORMs and application code may contain database-specific assumptions.
Performance differences
A query that performs well on MySQL may require different indexing or query design on PostgreSQL.
Hidden dependencies
Scheduled scripts, reporting tools, ETL jobs, APIs, and third-party integrations can depend on the existing database.
A thorough discovery process helps expose these dependencies before cutover.
A Practical Decision Framework
Before approving a MySQL-to-PostgreSQL migration, decision-makers should answer seven questions:
- Why are we migrating?
- What applications depend on the database?
- How much downtime can the business tolerate?
- How much database-specific code exists?
- What PostgreSQL hosting model will we use?
- How will we validate the migration?
- What is the rollback strategy?
The migration plan should not be approved until these questions have clear answers.
How to Choose a MySQL to PostgreSQL Migration Partner
When evaluating migration providers, look beyond the ability to copy data.
Ask whether the provider can demonstrate experience with:
- MySQL and PostgreSQL
- Schema conversion
- Stored procedures and triggers
- CDC
- Cloud database migration
- Application remediation
- Performance optimization
- Data validation
- Backup and rollback
- Production cutover
- Post-migration support
Also ask for a clear explanation of the migration methodology.
A strong migration proposal should explain what will be migrated, how it will be validated, what risks have been identified, how downtime will be controlled, and what happens if the cutover needs to be rolled back.
Conclusion
A MySQL-to-PostgreSQL migration is more than a database export and import. It is a modernization project involving schema, data, application behavior, infrastructure, security, performance, and operational processes.
For UK businesses, the right migration strategy depends on database size, application complexity, downtime requirements, cloud architecture, compliance needs, and internal engineering capabilities.
The most reliable approach is to begin with a technical assessment, select tooling based on the actual migration requirements, automate where practical, manually review database-specific logic, validate the target thoroughly, and rehearse the production cutover before the final migration.
The goal should not simply be:
"Move the data from MySQL to PostgreSQL."
The real objective is:
"Move the business to PostgreSQL without compromising data integrity, application reliability, security, or operational continuity."
Frequently Asked Questions
1. Can MySQL be migrated directly to PostgreSQL?
Yes, but the migration is not always a direct one-to-one conversion. Data can be migrated using tools such as AWS DMS, pgloader, scripts, or other migration utilities, while schema, SQL, stored procedures, triggers, and application dependencies may require additional conversion.
2. Which tool is best for MySQL to PostgreSQL migration?
There is no universally best tool. AWS DMS can be useful for managed migrations and CDC scenarios, while pgloader and custom scripts may be appropriate for other environments. Tool selection should be based on database size, downtime requirements, transformations, infrastructure, and operational constraints.
3. How long does a MySQL to PostgreSQL migration take?
It depends on database size, schema complexity, application dependencies, testing requirements, and downtime constraints. A small database with a simple application may be migrated relatively quickly, while a large enterprise system can require a multi-stage project lasting several weeks or longer.
4. How much does MySQL to PostgreSQL migration cost in the UK?
There is no reliable fixed price without assessing the environment. Costs depend on database size, application complexity, conversion effort, downtime requirements, cloud infrastructure, testing, and post-migration support.
5. Can the migration be performed with zero downtime?
Near-zero-downtime migrations may be possible using replication or CDC-based approaches, but the exact achievable downtime depends on the source database, application architecture, migration tooling, and cutover strategy. It should be validated during a migration rehearsal.
6. What happens to MySQL stored procedures?
Stored procedures generally need to be reviewed and, depending on their implementation, rewritten or adapted for PostgreSQL. Automated conversion can assist with some transformations, but complex business logic should be manually tested.
7. Will application code need to change after migration?
Potentially. Applications may contain MySQL-specific SQL, functions, data-type assumptions, ORM configurations, connection settings, or transaction behavior that needs to be updated for PostgreSQL.
8. How do you validate data after migration?
Validation can include row-count comparisons, key and relationship checks, aggregate comparisons, checksums where appropriate, sample-record verification, application testing, integration testing, and performance testing.
9. What is CDC in database migration?
Change Data Capture (CDC) tracks changes occurring in the source database after the initial data load. Those changes can be replicated to the target, allowing the target database to catch up before the final application cutover.
10. Should a UK business migrate MySQL to PostgreSQL?
The decision should be based on the organization's objectives, application requirements, operational constraints, and expected benefits. PostgreSQL may be appropriate for modernization and standardization initiatives, but a migration should be justified through a technical and business assessment rather than technology preference alone.
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