Flyway vs Liquibase vs ReactiveMongo: What are the differences?

# Introduction

Key differences between Flyway, Liquibase, and ReactiveMongo are outlined below:

1. **Database Migration Approach**: Flyway uses a version control approach where each migration script is identified by a version number, while Liquibase uses a changeset-based approach where each change is identified by a changeset ID. In contrast, ReactiveMongo does not directly handle database migration as it is a reactive MongoDB driver for Scala.

2. **Supported Databases**: Flyway and Liquibase support various relational databases like MySQL, PostgreSQL, Oracle, etc., whereas ReactiveMongo is specifically designed for MongoDB, a NoSQL database. 

3. **Concurrency Handling**: Flyway handles concurrency by locking the schema history table during migrations, ensuring only one migration runs at a time. Liquibase also has concurrency control mechanisms, such as using a database locking system or checksums for changesets. On the other hand, ReactiveMongo leverages the asynchronous and non-blocking nature of MongoDB to handle concurrency effectively.

4. **Integration with Build Tools**: Flyway integrates seamlessly with popular build tools like Maven and Gradle, providing plugins for easy automation. Liquibase also offers plugins for Maven, Gradle, and Ant to integrate with the build process. In comparison, ReactiveMongo can be easily integrated into Scala-based projects using SBT (Simple Build Tool) for managing dependencies.

5. **Error Handling and Rollback**: Flyway provides automatic rollback functionality in case of errors during migration, reverting changes made by the failed script. Liquibase offers similar rollback capabilities along with extensive error reporting for each change. However, ReactiveMongo does not have built-in support for automated rollback mechanisms as MongoDB handles transactions differently.

6. **Community and Support**: Flyway has a strong community backing with regular updates and documentation, along with professional support options. Liquibase also enjoys a large user community and provides commercial support for enterprise users. In contrast, ReactiveMongo has a smaller user base but is actively developed and maintained by the community.

# Summary
In conclusion, Flyway and Liquibase are popular choices for managing database migrations in relational databases, offering different approaches and features, whereas ReactiveMongo stands out as a reactive MongoDB driver tailored for Scala applications.