refactor(measurements): drop the write-only aggregation columns (migration 0272)

Migration 0263 added three columns beside the Apple Health `stats:*`
authority ladder. Only `aggregation_provenance` is ever read back: the
external-measurement reconciler selects it and refuses a lower-authority write
against a higher-authority canonical row, and the cumulative drain reads it
too. That column stays.

`aggregation_contributor_count` and `aggregation_selected_source_hash` are
written by three call sites and read by none. No select, no raw SQL, no export,
no backup, no API contract, no repair path. The import-time selection keeps its
deterministic tiebreak, which compares an in-memory map key computed per flush
rather than a value read back from the table.

Both are plain nullable scalars with no index, unique, check or foreign key, so
the drop is a catalog-only operation that touches no measured value.

prisma/migrations/0272_drop_write_only_aggregation_columns/migration.sql

@@ -0,0 +1,36 @@
+-- v1.32.35 — drop the two write-only aggregation columns on `measurements`.
+--
+-- Migration 0263 added three columns alongside the Apple Health `stats:*`
+-- authority ladder. Only one of them was ever read back:
+--
+--   * `aggregation_provenance` is load-bearing and STAYS. The external
+--     measurement reconciler selects it and refuses a lower-authority write
+--     against a higher-authority canonical row, which is what keeps an
+--     export.xml source-day estimate from clobbering a native HealthKit
+--     statistic. The cumulative drain reads it too.
+--   * `aggregation_contributor_count` and `aggregation_selected_source_hash`
+--     are written and never read. Three call sites write them (the batch
+--     ingest and the cumulative drain write explicit NULLs, the export.xml
+--     import writes real values); nothing selects them, no raw SQL names
+--     them, they reach no export, no backup, no API contract and no repair
+--     path. Verified by a repo-wide search over every tracked file for both
+--     the Prisma field names and the column names.
+--
+-- The import-time selection algorithm keeps its deterministic tiebreak: the
+-- source hash it compares is an in-memory map key computed per flush, not a
+-- value read back from this table. Only the persisted copies go.
+--
+-- DATA BOUNDARY — read before editing.
+--
+-- Both columns are plain nullable scalars added by 0263 with no index, no
+-- unique, no check and no foreign key, so `DROP COLUMN` rewrites the tuples of
+-- `measurements` and stops there. `DROP COLUMN` never cascades into another
+-- table on its own, and there is no CASCADE keyword here. No measured value,
+-- timestamp, unit, note or identity field is touched, and the documented
+-- LEGACY_UNKNOWN repair path operates on `aggregation_provenance`, which
+-- survives. In Postgres this is a catalog-only operation, so it is cheap even
+-- on the largest table in the schema.
+
+ALTER TABLE "measurements"
+  DROP COLUMN IF EXISTS "aggregation_contributor_count",
+  DROP COLUMN IF EXISTS "aggregation_selected_source_hash";

prisma/schema.prisma

@@ -1636,13 +1636,7 @@ model Measurement {
   // source-day estimate derived from export.xml; migrated ambiguous rows are
   // explicitly LEGACY_UNKNOWN until a native sync or archive reprocess repairs
   // them.
-  aggregationProvenance         MeasurementAggregationProvenance? @map("aggregation_provenance")
-  // Distinct source identities contributing to an export.xml source-day
-  // estimate. Source labels themselves are never persisted.
-  aggregationContributorCount   Int?                             @map("aggregation_contributor_count")
-  // SHA-256 of the deterministically selected source identity. Non-identifying
-  // provenance for repeatability without retaining device/source labels.
-  aggregationSelectedSourceHash String?                          @map("aggregation_selected_source_hash")
+  aggregationProvenance MeasurementAggregationProvenance? @map("aggregation_provenance")
   // Only set for BLOOD_GLUCOSE measurements. NULL for all others.
   glucoseContext        GlucoseContext?       @map("glucose_context")
   // v1.4.23 — per-stage sleep label. NULL for non-sleep rows; non-NULL

src/app/api/measurements/batch/route.ts

@@ -544,8 +544,6 @@ async function postBatch(request: NextRequest): Promise<Response> {
               .rhythmClassification as Prisma.MeasurementUncheckedCreateInput["rhythmClassification"],
             deviceType: p.row.deviceType as string | null,
             aggregationProvenance: statsRow ? "HEALTHKIT_STATISTICS" : null,
-            aggregationContributorCount: null,
-            aggregationSelectedSourceHash: null,
           },
           { exactExternalMatch: statsRow ? "update" : "duplicate" },
         ),

src/lib/measurements/__tests__/import-apple-health-export.test.ts

@@ -652,11 +652,7 @@ describe("streamParseExportXml — cumulative source-day estimates", () => {
     expect(prisma._measurements[0]).toMatchObject({
       value: 8_526,
       aggregationProvenance: "EXPORT_XML_SOURCE_MAX",
-      aggregationContributorCount: 2,
     });
-    expect(prisma._measurements[0]?.aggregationSelectedSourceHash).toMatch(
-      /^[a-f0-9]{64}$/,
-    );
     expect(result.cumulativeEstimates).toEqual({ days: 1, rows: 1 });
   });
 
@@ -675,7 +671,6 @@ describe("streamParseExportXml — cumulative source-day estimates", () => {
         type: mapping.measurementType,
         value: 30,
         aggregationProvenance: "EXPORT_XML_SOURCE_MAX",
-        aggregationContributorCount: 2,
       });
     },
   );
@@ -694,7 +689,6 @@ describe("streamParseExportXml — cumulative source-day estimates", () => {
       expect(prisma._measurements[0]).toMatchObject({
         type: mapping.measurementType,
         value: 50,
-        aggregationContributorCount: 1,
       });
     },
   );
@@ -712,7 +706,6 @@ describe("streamParseExportXml — cumulative source-day estimates", () => {
     expect(prisma._measurements).toHaveLength(1);
     expect(prisma._measurements[0]).toMatchObject({
       value: 100,
-      aggregationContributorCount: 1,
     });
   });
 
@@ -1171,7 +1164,6 @@ describe("streamParseExportXml — memory ceiling", () => {
     expect(prisma._measurements).toHaveLength(1);
     expect(prisma._measurements[0]).toMatchObject({
       value: 10_000,
-      aggregationContributorCount: 1,
     });
 
     // Heap delta should be modest — we tolerate a generous 100 MB so a

src/lib/measurements/__tests__/reconcile-external-measurement.test.ts

@@ -40,8 +40,6 @@ function row(overrides: Record<string, unknown> = {}): Record<string, unknown> {
     externalId: "sleep:new",
     externalSourceVersion: null,
     aggregationProvenance: null,
-    aggregationContributorCount: null,
-    aggregationSelectedSourceHash: null,
     glucoseContext: null,
     sleepStage: "DEEP",
     rhythmClassification: null,
@@ -224,8 +222,6 @@ describe("reconcileExternalMeasurement", () => {
       sleepStage: null,
       externalId: "stats:HKQuantityTypeIdentifierStepCount:2026-07-20",
       aggregationProvenance: "HEALTHKIT_STATISTICS",
-      aggregationContributorCount: null,
-      aggregationSelectedSourceHash: null,
     });
     const { tx, measurement } = transaction([native]);
 
@@ -240,8 +236,6 @@ describe("reconcileExternalMeasurement", () => {
         sleepStage: null,
         externalId: "stats:HKQuantityTypeIdentifierStepCount:2026-07-20",
         aggregationProvenance: "EXPORT_XML_SOURCE_MAX",
-        aggregationContributorCount: 2,
-        aggregationSelectedSourceHash: "source-hash",
       }),
       { exactExternalMatch: "update" },
     );
@@ -350,8 +344,6 @@ describe("reconcileExternalMeasurement", () => {
         sleepStage: null,
         externalId: "stats:HKQuantityTypeIdentifierStepCount:2026-07-20",
         aggregationProvenance: "HEALTHKIT_STATISTICS",
-        aggregationContributorCount: null,
-        aggregationSelectedSourceHash: null,
       }),
       { exactExternalMatch: "update" },
     );
@@ -366,8 +358,6 @@ describe("reconcileExternalMeasurement", () => {
         data: expect.objectContaining({
           value: 8_600,
           aggregationProvenance: "HEALTHKIT_STATISTICS",
-          aggregationContributorCount: null,
-          aggregationSelectedSourceHash: null,
           syncVersion: { increment: 1 },
         }),
       }),

src/lib/measurements/drain-per-sample-cumulative.ts

@@ -352,8 +352,6 @@ export async function drainPerSampleCumulative(
                   externalId,
                   deletedAt: null,
                   aggregationProvenance: "LEGACY_UNKNOWN",
-                  aggregationContributorCount: null,
-                  aggregationSelectedSourceHash: null,
                   syncVersion: { increment: 1 },
                   ...(slotIsFreeForTarget
                     ? { measuredAt: canonicalTimestamp }

src/lib/measurements/import-apple-health-export.ts

@@ -680,7 +680,10 @@ export async function streamParseExportXml(
           }
         }
         if (!selected) continue;
-        const [selectedSourceHash, selectedSubtotal] = selected;
+        // Only the subtotal is carried forward. The source hash stays an
+        // in-memory map key — it is what makes the max-subtotal selection
+        // above deterministic on a tie, and it is not persisted.
+        const [, selectedSubtotal] = selected;
         if (validateMeasurementRange(type, selectedSubtotal) !== null) {
           unknown[`${type}::aggregate_out_of_range`] =
             (unknown[`${type}::aggregate_out_of_range`] ?? 0) + 1;
@@ -704,8 +707,6 @@ export async function streamParseExportXml(
               sleepStage: null,
               deviceType: null,
               aggregationProvenance: "EXPORT_XML_SOURCE_MAX",
-              aggregationContributorCount: bySource.size,
-              aggregationSelectedSourceHash: selectedSourceHash,
             },
             { exactExternalMatch: "update" },
           ),

tests/integration/measurement-identity-reconcile.test.ts

@@ -114,8 +114,6 @@ describe("external measurement identity reconciliation (real Postgres)", () => {
             measuredAt: new Date("2026-07-20T09:00:00.000Z"),
             sleepStage: null,
             aggregationProvenance: "EXPORT_XML_SOURCE_MAX",
-            aggregationContributorCount: 2,
-            aggregationSelectedSourceHash: "xml-source-hash",
           },
         ),
       },
@@ -132,8 +130,6 @@ describe("external measurement identity reconciliation (real Postgres)", () => {
           externalSourceVersion: "native-v1",
           deviceType: "Apple Watch",
           aggregationProvenance: "HEALTHKIT_STATISTICS",
-          aggregationContributorCount: null,
-          aggregationSelectedSourceHash: null,
         }),
       },
     });
@@ -147,8 +143,6 @@ describe("external measurement identity reconciliation (real Postgres)", () => {
         measuredAt: nativeMeasuredAt,
         sleepStage: null,
         aggregationProvenance: "EXPORT_XML_SOURCE_MAX",
-        aggregationContributorCount: 2,
-        aggregationSelectedSourceHash: "xml-source-hash",
       }),
       { exactExternalMatch: "update" },
     );
@@ -171,8 +165,6 @@ describe("external measurement identity reconciliation (real Postgres)", () => {
       externalSourceVersion: "native-v1",
       deviceType: "Apple Watch",
       aggregationProvenance: "HEALTHKIT_STATISTICS",
-      aggregationContributorCount: null,
-      aggregationSelectedSourceHash: null,
     });
     expect(
       await prisma.measurement.findUniqueOrThrow({
@@ -194,8 +186,6 @@ describe("external measurement identity reconciliation (real Postgres)", () => {
         externalSourceVersion: "native-v2",
         deviceType: "Apple Watch",
         aggregationProvenance: "HEALTHKIT_STATISTICS",
-        aggregationContributorCount: null,
-        aggregationSelectedSourceHash: null,
       }),
       { exactExternalMatch: "update" },
     );

tests/integration/measurements-batch.test.ts

@@ -601,8 +601,6 @@ describe("POST /api/measurements/batch (real Postgres)", () => {
       expect(stored[0]!.value).toBeCloseTo(5200, 5);
       expect(stored[0]).toMatchObject({
         aggregationProvenance: "HEALTHKIT_STATISTICS",
-        aggregationContributorCount: null,
-        aggregationSelectedSourceHash: null,
         syncVersion: 2,
       });
     });
@@ -1217,7 +1215,6 @@ describe("POST /api/measurements/batch (real Postgres)", () => {
       expect(estimated[0]).toMatchObject({
         value: 8_526,
         aggregationProvenance: "EXPORT_XML_SOURCE_MAX",
-        aggregationContributorCount: 2,
         syncVersion: 1,
       });
 
@@ -1235,8 +1232,6 @@ describe("POST /api/measurements/batch (real Postgres)", () => {
       expect(canonical[0]).toMatchObject({
         value: 8_600,
         aggregationProvenance: "HEALTHKIT_STATISTICS",
-        aggregationContributorCount: null,
-        aggregationSelectedSourceHash: null,
         syncVersion: 2,
       });
     });
@@ -1297,7 +1292,6 @@ describe("POST /api/measurements/batch (real Postgres)", () => {
       expect(rows[0]).toMatchObject({
         value: 8_526,
         aggregationProvenance: "EXPORT_XML_SOURCE_MAX",
-        aggregationContributorCount: 2,
         syncVersion: 2,
       });
     });