Logical Replication from MySQL, SQL Server and Oracle to PostgreSQL?

Introduction

PostgreSQL has become a go-to database for analytics, reporting, and modern application development, thanks to its extensibility, powerful indexing, and advanced features like JSONB, GIS, and vector processing. However, many organizations still rely on traditional relational databases like MySQL, SQL Server, and Oracle for their operational workloads. The need to replicate real-time data from these heterogeneous databases into PostgreSQL has grown significantly for reporting, analytics, and data warehousing purposes.

Logical replication enables real-time data streaming between different databases without requiring a complete migration. Unlike physical replication, logical replication allows selective data synchronization at the table or row level, making it ideal for cross-platform data movement. In this blog, we will explore the challenges, solutions, and best practices for setting up logical replication from MySQL, SQL Server, and Oracle to PostgreSQL.

Challenges in Cross-Database Replication

Replicating data across different database vendors comes with several challenges:

1. Schema Differences: Each database has its own data types, indexing mechanisms, and schema structures, which require careful mapping when replicating data.
2. Change Data Capture (CDC) Mechanisms: MySQL, SQL Server, and Oracle each have different CDC approaches, such as binary logs, transaction logs, and LogMiner, making unified replication complex.
3. Performance Overhead: Real-time replication needs to be efficient and lightweight to avoid degrading source database performance.
4. Data Consistency and Conflict Handling: Ensuring data integrity across distributed systems requires conflict resolution strategies, especially when dealing with high-throughput transactional databases.
5. Tooling and Complexity: Many existing replication solutions require complex setups, additional middleware, or specialized configurations. Debezium and Oracle Golden Gate are 2 examples.

Approaches for Logical Replication to PostgreSQL

1. Using Debezium for CDC-Based Replication

Debezium is an open-source CDC platform that captures real-time changes from MySQL, SQL Server, and Oracle (and several other source databases) and streams them to PostgreSQL (and several other destination databases). It integrates with Apache Kafka, providing a scalable solution for event-driven replication.

• MySQL: Uses binary logs (binlog) to capture row-level changes.
• SQL Server: Uses transaction log-based CDC or Change Tracking.
• Oracle: Utilizes LogMiner to capture committed transactions.
• PostgreSQL Integration: Streams CDC events via Kafka Connect or Debezium embedded mode to PostgreSQL tables.

2. Using Foreign Data Wrappers (FDWs)

PostgreSQL supports Foreign Data Wrappers (FDWs) for integrating external databases:

• mysql_fdw for MySQL
• tds_fdw for SQL Server
• oracle_fdw for Oracle

FDWs allow querying and joining data from remote databases directly within PostgreSQL. However, they do not support real-time replication and are best suited for federated queries.

3. Using Custom Scripting and ETL Pipelines

For some use cases, custom scripts using Python, SQL, or ETL tools like Apache NiFi, Talend, or AWS DMS (Database Migration Service) can be an effective way to synchronize data between databases. These approaches provide flexibility but often require additional monitoring and maintenance.

4. Using SynchDB for Seamless Logical Replication

SynchDB is a PostgreSQL extension designed to enable real-time logical replication from heterogeneous databases. Unlike traditional CDC tools, SynchDB provides:

• Direct integration with PostgreSQL
• Flexible data transformation for mapping schema differences
• Efficient transaction streaming with low overhead
• Simplified setup without external middleware

By leveraging SynchDB, organizations can achieve seamless logical replication from MySQL, SQL Server, and Oracle into PostgreSQL with minimal configuration or environment setup efforts.

Best Practices for Cross-Database Logical Replication

1. Ensure Schema Compatibility: Use tools like pgloader, ora2pg, or schema conversion tools to map data types and indexes correctly.
2. Monitor Replication Performance: Use PostgreSQL’s pg_stat_subscription and other monitoring tools to track replication latency.
3. Optimize Network Throughput: Ensure that network bandwidth is sufficient for high-volume transaction replication.
4. Handle Data Conflicts Gracefully: Implement conflict resolution strategies, such as last-write-wins or timestamp-based merging.
5. Test Before Deployment: Validate replication on a staging environment before applying it to production.

How SynchDB Can Help?

SynchDB is a new and emerging ETL solution designed as a PostgreSQL-native extension to streamline logical replication from MySQL, SQL Server, and Oracle directly into PostgreSQL. Unlike external CDC tools that require additional infrastructure (e.g., Kafka or third-party middleware), SynchDB operates inside PostgreSQL, making it:

• Lightweight: No need for external services like Kafka or middleware.
• Real-time: Captures and applies changes directly within PostgreSQL.
• Schema-Aware: Automatically handles data type conversion and schema changes with rules file for user to define custom type mappings.
• Flexible: Supports table-level replication, filtering, and transformation.
• Easy to Integrate: Works as a PostgreSQL extension, requiring minimal configuration.

Key Features of SynchDB

1. Real-time Change Capture – Uses Debezium-based CDC to track inserts, updates, and deletes and DDL changes.
2. Direct PostgreSQL Integration – Runs as a native extension, reducing latency and complex infrastructure setup.
3. Data Type Compatibility – Automatically maps MySQL, SQL Server, and Oracle types to PostgreSQL equivalents.
4. Schema Evolution Support – Detects and adjusts for table structure changes dynamically.
5. Error Handling & Logging – Provides detailed logs and strategies for handling replication failures.

With SynchDB, organizations can seamlessly transition to PostgreSQL while ensuring data consistency and integrity across databases. It is an open-source and on-going project and you can learn more about it here.

Conclusion

Logical replication from MySQL, SQL Server, and Oracle to PostgreSQL enables organizations to unify their data infrastructure, improve analytics, and modernize their database stack. Whether using Debezium, FDWs, custom ETL pipelines, or the SynchDB extension, choosing the right approach depends on factors like replication latency, complexity, and transformation needs.

With the right tools and best practices, PostgreSQL can become the central hub for data integration, providing a scalable and flexible solution for heterogeneous database environments.