H2 in Oracle compatibility mode is validated as H2, not oracle - oracle

Question

In production I'm using Oracle and all my changelogs have been written with Oracle in mind.
In my development environment I'm trying to generate the changelogs on an H2 instance in Oracle compatibility mode.
This is to improve integration test speed.
My problem is that Liquibase is validating my changelogs against H2, not Oracle.
Is there a way of forcing Liquibase to validate against Oracle even though my db url looks like an H2 one?
My biggest headaches are regarding sequences and dropNotNullConstraint validations.
Liquibase version: 2.0.5 (I also tried with 3.1.1, same issue)
H2 connection url: jdbc:h2:tcp://localhost:9092/test;MODE=Oracle;AUTO_SERVER=TRUE;DB_CLOSE_DELAY=-1
I'm pretty sure this is a common scenario so I guess I'm probably doing something wrong?
any help would be greatly appreciated

Answer 1

Since Liquibase is implemented in Java and relies on JDBC I'll use Java for explanation.
Liquibase has a list of implemented databases. It depends how you call it from Java code but let's say you either use liquibase.database.DatabaseFactory, extend it or implement something similar. Usually your code would look something like this (example in Scala):
def createLiquibase(dbConnection: Connection, diffFilePath: String): Liquibase = {
val database = DatabaseFactory.getInstance.findCorrectDatabaseImplementation(new JdbcConnection(dbConnection))
val classLoader = classOf[SchemaMigration].getClassLoader
val resourceAccessor = new ClassLoaderResourceAccessor(classLoader)
new Liquibase(diffFilePath, resourceAccessor, database)
}
def updateDb(db: DbConnectionProvider, diffFilePath: String): Unit = {
val dbConnection = db.getConnection
val liquibase = createLiquibase(dbConnection, diffFilePath)
try {
liquibase.update(null)
} catch {
case e: Throwable => throw e
} finally {
liquibase.forceReleaseLocks()
dbConnection.rollback()
dbConnection.close()
}
}
Notice this part DatabaseFactory.getInstance.findCorrectDatabaseImplementation(new JdbcConnection(dbConnection)) where we pass in java.sql.Connection and Liquibase finds appropriate Database implementation for it. You can override findCorrectDatabaseImplementation or even create your own Database subclass altogether. Whatever you prefer.
The method in DatabaseFactory is public Database findCorrectDatabaseImplementation(DatabaseConnection connection) throws DatabaseException. From there you can learn more about what Database type is. You can inherit it from H2 or Oracle and override some parts.
If you use Liquibase cmd client you could do what I described above, build a jar file or such and then run from command line making sure your new classes on the classpath.
Compatibilty mode in H2 does not guarantee complete support of Oracle, Postgres, etc, so it's a bit dubious idea to test Oracle DML on it. It will probably work until you find when it doesn't.