Database Vendors

IAM owns its schema via its own dedicated Flyway instance — history table iam_flyway_history, never your flyway_schema_history — and partitions migrations by vendor (one consolidated V1 per vendor since 2.0.0):

db/iam/migration/
├── postgresql/   V1__create_iam_schema.sql   (default)
└── mysql/        V1__create_iam_schema.sql

The active set is selected by one property: iam.database.vendor resolves classpath:db/iam/migration/<vendor>. Your spring.flyway.* configuration is never read or modified by IAM — hosts with their own migrations keep vanilla Spring Boot defaults. To take over IAM’s schema management entirely, set iam.database.migrations-enabled: false.

PostgreSQL (default)

Nothing to configure beyond your datasource:

spring:
  datasource:
    url: jdbc:postgresql://localhost:5432/myapp

runtimeOnly("org.postgresql:postgresql")
runtimeOnly("org.flywaydb:flyway-core")
runtimeOnly("org.flywaydb:flyway-database-postgresql")

Uses native UUID, JSONB, and TIMESTAMP types.

MySQL

iam:
  database:
    vendor: mysql
spring:
  datasource:
    url: jdbc:mysql://localhost:3306/myapp

runtimeOnly("com.mysql:mysql-connector-j")
runtimeOnly("org.flywaydb:flyway-core")
runtimeOnly("org.flywaydb:flyway-mysql")

Requires MySQL 8.0.13+ (expression defaults, functional indexes). The MySQL schema maps types deliberately:

PostgreSQL	MySQL	Why
UUID	BINARY(16)	Hibernate 6’s default UUID mapping on MySQL
JSONB	JSON	native JSON on both
TEXT[]	JSON array	MySQL has no arrays; entities map List<String> as JSON on every vendor
TIMESTAMP	DATETIME(6)	no 2038 limit, no TIMESTAMP auto-init quirk
gen_random_uuid() default	(UUID_TO_BIN(UUID()))	expression defaults

The entity mappings are vendor-neutral (@JdbcTypeCode(SqlTypes.JSON), no hardcoded dialect), and the schema is verified on every boot by ddl-auto: validate — a green start is the parity check. The repository ships a MySQL Testcontainers parity suite covering migrations, JSON/array round-trips, and end-to-end permission resolution.

One deliberate divergence

MySQL’s iam_user_roles junction table has no surrogate primary key: on MySQL any DB-side random UUID is unsafe under statement-based replication, and nothing in the application reads that column. Its functional unique index over (user, role, scope) is the row identity.

Don’t pin the dialect

Do not set hibernate.dialect yourself — Hibernate 6 auto-detects the right dialect from JDBC metadata. A pinned PostgreSQL dialect against MySQL fails at boot with sequence-discovery errors.

Adding another vendor

1. Author db/iam/migration/<vendor>/V1__create_iam_schema.sql translating the DDL (mind: UUID storage, JSON type, timestamp semantics, upsert syntax).
2. Set iam.database.vendor: <vendor> and add the driver + Flyway support module.
3. Boot with ddl-auto: validate against a real instance — validation failures are your parity TODO list, one column at a time.