ADR-0022: Quantity-Tracked Items & Asset Sets

• Status: Proposed
• Date: 2026-09-24
• Related: ADR-0006, ADR-0013, ADR-0014

Context

Not everything is a uniquely identifiable asset. Clubs own "40 caps size M", "25 music stands", "a box of lyres (marching music holders)". A drum kit is several pieces sharing one purchase and sometimes one serial. Forcing one row per item makes data entry painful and imports messy.

Decision

• assets.tracking = individual (default, one physical item) | quantity (a stock line).
• Quantity assets have quantity_total. Assignments of quantity assets carry quantity (≥ 1). The partial unique index "one open assignment per asset" applies only to individual assets. For quantity assets, a check ensures the sum of open assignment quantities ≤ quantity_total (enforced in a transaction with SELECT … FOR UPDATE on the asset row).
• Forecasting: purchase price and insured value are per unit for quantity assets and are multiplied by quantity_total. Partial replacement isn't modelled in v1.
• Sets: assets.parent_asset_id (nullable, same tenant) groups components (drum kit → snare, toms, cymbals). Checking out the parent checks out all components that aren't individually assigned. Each component keeps its own serial/value when known.
• Import (ADR-0014) maps an "Aantal/Quantity" column to quantity tracking.

Consequences

• Clothing and accessories become practical to manage. Uniform sizes use custom fields (ADR-0013), one stock line per size.
• The assignment and forecast logic gains one branch each, covered by table-driven tests.