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fix(db): store rollup cost columns as double precision #3715

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fix(db): store rollup cost columns as double precision #3715

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2f7b632
refactor(db): store rollup cost columns as double precision
pacocartones Aug 20, 2026
5e986f1
test(db): assert rollup cost columns are double precision
pacocartones Aug 20, 2026
1a67d50
chore(db): migration widening rollup cost columns to double precision
pacocartones Aug 23, 2026
29a76dd
test(admin): expect exact sums now costs are double precision
pacocartones Aug 23, 2026
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26 changes: 12 additions & 14 deletions apps/api/src/routes/admin-global-stats.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -60,10 +60,9 @@ const BUCKETS: Bucket[] = [
];

// The per-bucket fixture above also lands in the window every query covers.
const BASE_FIXTURE_COST = BUCKETS.reduce(
(sum, bucket) => sum + Math.fround(bucket.cost),
0,
);
// The cost columns are double precision, so these literals round-trip exactly
// and the expectation is simply their sum.
const BASE_FIXTURE_COST = BUCKETS.reduce((sum, bucket) => sum + bucket.cost, 0);

interface GlobalStatsResponse {
totals: {
Expand Down Expand Up @@ -244,12 +243,11 @@ describe("admin — global stats mode/kind dimensions", () => {
).toBe("default");
});

// Costs are stored in float4 columns. Summing them *as* float4 (Postgres'
// default for SUM(real)) runs out of significant digits well before the
// all-time totals this page shows, and the error depends on how the rows were
// grouped — so the headline stopped matching the slices underneath it. A
// handful of rows never showed it; the drift only appears at production
// magnitude, hence the bulk fixture.
// Costs are stored in double precision columns and summed in NUMERIC, so the
// all-time totals this page shows are exact however the rows were grouped.
// Under the previous float4 storage the headline stopped matching the slices
// underneath it. A handful of rows never showed it; the drift only appears at
// production magnitude, hence the bulk fixture.
test("large all-time sums stay exact and grouping-independent", async () => {
const DAYS = 700;
const PER_ROW_COST = 4321.1234;
Expand Down Expand Up @@ -293,11 +291,11 @@ describe("admin — global stats mode/kind dimensions", () => {
expect(byKind).toBeCloseTo(body.totals.cost, 2);
expect(timeseriesTotal).toBeCloseTo(body.totals.cost, 2);

// float4 rounds PER_ROW_COST on the way in, so compare against the value
// the column actually holds rather than the literal above.
const stored = Math.fround(PER_ROW_COST);
// Double precision holds PER_ROW_COST exactly, so the total must match the
// literal rather than a storage-rounded stand-in. The same fixture drifted
// by ~0.38 under float4 storage, far beyond a cent.
expect(body.totals.cost).toBeCloseTo(
stored * DAYS * BUCKETS.length + BASE_FIXTURE_COST, // eslint-disable-line no-mixed-operators
PER_ROW_COST * DAYS * BUCKETS.length + BASE_FIXTURE_COST, // eslint-disable-line no-mixed-operators
2,
);
});
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