Declare the subscription-movement grain before joining invoice lines
A report doubles subscription movement when a contract has two invoice lines in the same month.
- Focused work estimate
- 1h 30m + prerequisites
- Priority in the scenario
- Medium
- Engineering practice
- Dimensional modeling · SQL
Estimated field mix
- Data engineering70%
- Database engineering30%
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 SaaS analyst reports expansion revenue differently from finance because snapshots, refunds and contract changes are joined at incompatible grains.
Setup prerequisites
- Create a synthetic source schema and local transformation project.
- Use integer minor units and distinct reporting currencies.
Preceding work
No earlier ticket is required. Complete the project setup above.
Acceptance criteria
- Document one row per subscription, period and currency.
- Identify source keys and permitted multiplicity.
- Reject duplicate grain keys in a contract check.
Implementation constraints
- Create a small synthetic multi-line invoice example.
Verification to include
- Reconcile a two-line invoice to one movement row.
- Insert duplicate source identity and fail the grain check.
Deliverables
- Grain specification and executable uniqueness check
Rollout and recovery
Review the grain contract before enabling downstream joins.
Value of the work
For the engineer: Practice analytical modeling and explainable transformation contracts.
For the team: Review trustworthy reporting definitions and the cost of correcting historical reports.
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.