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Document the nullable lodged_* migration for the FE/Drizzle owner

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Specifies the ALTER ... DROP NOT NULL on the four lodged_* columns (#1361) and
the ordering constraint: it must land before the backend writes NULL or runs the
backfill, else the predicted-Property INSERT aborts the batch.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
This commit is contained in:
Khalim Conn-Kowlessar 2026-06-30 22:19:54 +00:00
parent 7e06aa63c6
commit 09b3bc98ba
1 changed files with 19 additions and 4 deletions
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23
docs/migrations/property-baseline-performance-table.md
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@ -18,10 +18,10 @@ straight lift-and-shift of the columns below.
|---|---|---|
| `id` | serial PK | |
| `property_id` | int, FK → `property.id`, **unique** | one Baseline Performance per Property |
| `lodged_sap_score` | int | Lodged Performance — gov register, off the Effective EPC |
| `lodged_epc_band` | text | the `Epc` enum, stored as its string value (e.g. `"C"`) |
| `lodged_co2_emissions_t_per_yr` | float | tonnes CO₂/yr (whole dwelling) |
| `lodged_primary_energy_intensity_kwh_per_m2_yr` | int | PEUI (kWh/m²/yr); **not** "heat demand" — see CONTEXT.md |
| `lodged_sap_score` | int, **nullable** | Lodged Performance — gov register, off the Effective EPC. **NULL for a predicted Property** (no lodged cert — #1361, see below) |
| `lodged_epc_band` | text, **nullable** | the `Epc` enum, stored as its string value (e.g. `"C"`) |
| `lodged_co2_emissions_t_per_yr` | float, **nullable** | tonnes CO₂/yr (whole dwelling) |
| `lodged_primary_energy_intensity_kwh_per_m2_yr` | int, **nullable** | PEUI (kWh/m²/yr); **not** "heat demand" — see CONTEXT.md |
| `effective_sap_score` | int | Effective Performance — what modelling scored against |
| `effective_epc_band` | text | |
| `effective_co2_emissions_t_per_yr` | float | tonnes CO₂/yr (whole dwelling) |
@ -30,6 +30,21 @@ straight lift-and-shift of the columns below.
| `space_heating_kwh` | float | EPC `renewable_heat_incentive` recorded demand. **Superseded** by `heating_kwh` (delivered) when the bill block populates; kept until then to avoid an empty-kWh gap, dropped in the population slice. |
| `water_heating_kwh` | float | EPC `renewable_heat_incentive`; **superseded** by `hot_water_kwh`. |
### Lodged half is nullable (#1361 Class B, 2026-06-30)
The four `lodged_*` columns are **nullable**. A **predicted** Property (EPC Prediction, ADR-0029/0031:
no lodged cert, its `EpcPropertyData` synthesised from neighbours) has **no Lodged Performance** — the
backend now writes `lodged_* = NULL` for it and persists only the Effective half (ADR-0004 amendment).
Reading the synthesised EPC's recorded fields as a lodged figure had been manufacturing a phantom (a
neighbour's SAP), which the migration + a one-time backfill remove.
**FE-owned Drizzle migration required:** `ALTER TABLE property_baseline_performance ALTER COLUMN
lodged_sap_score DROP NOT NULL` (and the same for `lodged_epc_band`, `lodged_co2_emissions_t_per_yr`,
`lodged_primary_energy_intensity_kwh_per_m2_yr`). This **must land before** the backend deploys the
orchestrator change or runs `scripts/null_predicted_lodged_performance.py` — a `NULL` write against a
`NOT NULL` column aborts the batch (ADR-0012). The backfill NULLs the four columns on the ~12,236
existing predicted-source rows; Effective, the bill block, and `rebaseline_reason` are left intact.
### Bill block (ADR-0014) — the energy bill, composed per section
Produced by **Bill Derivation**: the calculator's **delivered** kWh per end use priced at current