PPalabas APIJava field course

World 2A / Quest 2A.1

Cinema and Screen Schema

Create the first Flyway migration for cinemas and screens before any JPA entity exists.

Concept

Phase 2A starts where most tutorials end: with the database saying what the system means. Cinemas and screens are small, but they already carry real invariants: zone IDs, source-aware identity, coordinates, ownership, and capacity.

Task

  1. Create the Flyway V1 migration with cinemas and screens.
  2. Add source-system-aware uniqueness for cinemas.
  3. Add check constraints for coordinates and screen capacity.
  4. Update the ERD and schema notes with each invariant.

Run

docker compose up -d postgres
./gradlew flywayMigrate
./gradlew test --tests "*Phase2ASchemaContractTest"

Expected Result

  • Flyway applies V1.
  • The schema contract test finds the cinema and screen constraints.

Common Traps

  • Using a fixed UTC offset instead of an IANA zone ID.
  • Making source_external_id unique without source_system.
  • Leaving capacity validation only in Java.

Hint Ladder

Hint 1

The timezone column is a string, but Java validates it with ZoneId.

Hint 2

Two providers can both call something 123. The source is part of the identity.

Hint 3

A screen cannot exist without a cinema, so make the FK non-null.

Solution

See palabas-api/src/main/resources/db/migration/V1__schema.sql.

Boot 3 to 4 Delta

Boot is not the main lesson here. The important delta is resisting ddl-auto and letting Flyway own schema history.