How To move to Spring Boot 2 and Flyway 5 from Spring Boot 1.5 and Flyway 3

I had to figure this out the hard way, as soon as we upgraded our project from Spring Boot 1.5 to Spring Boot 2, all our existing migrations written using Flyway 3 started bombing.

After reading the docs I realised that the migration schema used by Flyway 3 isn't compatible with Flyway 5. What's more, there is not direct upgrade path from Flyway 3 to Flyway 5.

According to the official documentation we need to do the following:

• First upgrade your 1.5.x Spring Boot application to Flyway 4 (4.2.0 at the time of writing), see the instructions for Maven and Gradle. 

• Once your schema has been upgraded to Flyway 4, upgrade to Spring Boot 2 and run the migration again to port your application to Flyway 5.

This essentially means we will have to do two releases, which I didn't really want to do. Another approach to getting this fixed is described here. I haven't tried it but it should work.

For me, all I wanted was to get my project upgraded and working. I had a few migrations but I also had lots of DB snapshots which we could use to restore the old database. Hence, I decided to take the easy way out. I looked for ways to ignore the existing migrations, in the Flyway documentation we were able to find two settings that could be used. 

# Whether to automatically call baseline when migrate is executed against a non-empty schema with no schema history
# table. This schema will then be initialized with the baselineVersion before executing the migrations.
# Only migrations above baselineVersion will then be applied.
# This is useful for initial Flyway production deployments on projects with an existing DB.
# Be careful when enabling this as it removes the safety net that ensures
# Flyway does not migrate the wrong database in case of a configuration mistake! (default: false)
flyway.baselineOnMigrate=true

# The version to tag an existing schema with when executing baseline. (default: 1)
flyway.baselineVersion=20200131132000

As the documentation suggest, basically it will ignore all the migrations till the version 20200131132000 and thats exactly what we wanted to do.

When using these settings with Spring Boot you need to append "spring." to them hence, the final settings added in application.properites file are:

spring.flyway.baselineOnMigrate=true
spring.flyway.baselineVersion=20200131132000

That did it for us, the project was up and running with Spring Boot 2 and Flyway 5. After this point if we wrote new migrations those worked as well.