Migrating databases of different schema versions automagically using Flyway

Question

I think the documentation (http://flywaydb.org/getstarted/existingDatabaseSetup.html) is not clear enough and would like the description to be illustrated with an example. I have one for you:

Let's say we have two different versions (1 and 2) of the production database whose schema version is implicit but deterministic by querying the existing tables. How will we then achieve what is described in the documentation?

In my example the two versions both have a script attached: Version 1: Create table A Version 2: Create table B

I have created java migration files matching the scripts for versions 1 and 2 but since the flyway metadata is missing I need to query the database whether the scripts have been run and skip them in that case. The problem is that the application crashes since Flyway has not been initialised.

I don't want to initialise Flyway from the commandline since I want this to be done automatically upon deployment (Flyway in embedded mode). From what I've seen this only works with empty databases. Is there a simple solution to this problem?

Answer 1

For single PROD databases, you can use flyway.initOnMigrate

In your case you would have to wrap Flyway and recreate this manually by inspecting your tables and calling either init with flyway.initialVersion=1 or with flyway.initialVersion=2, followed by a call to migrate.