Add nullable customer-ID references to dependent tables
Case rows need the new relationship without requiring a single locking rewrite of the entire dataset.
- Focused work estimate
- 1h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Schema evolution · Foreign keys
Estimated field mix
- Database engineering100%
Field percentages are editorial estimates of the ticket's engineering focus. They total 100%; they are not measured time, proficiency scores, or ownership evidence.
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Project context
A fictional support platform stores a mutable external account code as its primary relationship key. Renames and imports now break references in several tables.
Setup prerequisites
- Create a disposable database with synthetic customers and dependent records.
- Apply real migration files; never use production db push.
Preceding work
Complete these dependencies, or supply their agreed outputs before taking this ticket.
Acceptance criteria
- Add the new foreign-key columns without changing current reads.
- Index the intended lookup boundary where needed.
- Document the later validation and non-null steps.
Implementation constraints
- Keep migration operations explicit and bounded to the selected tables.
Verification to include
- Insert an old-client case after the additive migration.
- Insert an invalid non-null customer ID and verify the intended foreign-key behavior.
Deliverables
- Dependent-table expansion migration
Rollout and recovery
Deploy schema before bridge writers; remove unused new columns only before any consumer relies on them.
Value of the work
For the engineer: Practice migration ordering, compatibility and referential integrity.
For the team: Review a reversible schema transition with measurable completeness checks.
Evidence boundaries
Outcome Evidence: Tests, patches, and runbooks are requested deliverables. They become Outcome Evidence only through a qualified Mission and immutable Evidence IDs.
Ownership Evidence: Independent adaptation must be observed under a declared verification policy and cite immutable Evidence IDs. Completing a planning ticket establishes no Ownership Evidence.