objectstack-ai
diff --git a/‎.changeset/21485-date-bucket-calendar-day.md‎
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diff --git a/‎packages/drivers/driver-sql/src/sql-driver-21485-date-bucket-calendar-day.test.ts‎
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diff --git a/‎packages/drivers/driver-sql/src/sql-driver-temporal-dialect.test.ts‎
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@@ -0,0 +1,11 @@
+---
+'@objectstack/driver-sql': patch
+---
+
+A `Field.date` grouped by `day`, `week`, `month`, `quarter` or `year` buckets as its own calendar day on PostgreSQL and MySQL, whatever zone the server or the session is in (#21485).
+
+Clause-②: no
+
+- **What was wrong.** The PostgreSQL bucket cast every column to `timestamptz` and the MySQL bucket passed every column through `convert_tz`. A `date` has no instant, so both invented midnight in the session's zone, and on a session east of UTC the conversion to UTC read the previous day. On PostgreSQL with the server at `Asia/Shanghai`, `2026-06-01` grouped into month `2026-05`, and `2026-01-01` into year `2025`. MySQL did the same once the session zone was `+08:00`; the driver pins its own sessions to UTC, so there it took a host `pool.afterCreate` that sets the session zone.
+- **What it does now.** A declared `Field.date` buckets its calendar day with no zone conversion. A `Field.datetime`, and a column with no declaration, keep the UTC-instant expression, byte for byte. SQLite already bucketed a `date` as its calendar day and is unchanged.
+- **Where it shows.** `aggregate()` with a `dateGranularity` group, and the expression `SqlDriver.dateBucketSql()` renders for the analytics SQL echo, which reads the same expression.
@@ -0,0 +1,272 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * [#21485] A `Field.date` buckets as its own calendar day, whatever zone the
+ * server or the session is in. A `Field.datetime` buckets as its UTC instant.
+ *
+ * ## The defect this pins closed
+ *
+ * `buildDateBucketExpr` used one expression per dialect for every column it
+ * bucketed, the instant one: `to_char((col)::timestamptz AT TIME ZONE 'UTC', …)`
+ * on PostgreSQL and `date_format(convert_tz(col, @@session.time_zone, '+00:00'), …)`
+ * on MySQL. A `date` has no instant, so the cast INVENTED one: midnight in the
+ * session's zone. On a session east of UTC that midnight is the previous UTC
+ * day, and the UTC conversion then read the day before. Measured on
+ * PostgreSQL 16.14 with the server's `TimeZone` at `Asia/Shanghai`, and on
+ * MySQL 8.0.46 with the session at `+08:00`, both before the fix:
+ *
+ * | `Field.date` value | day          | week       | month     | quarter   | year   |
+ * |:--|:--|:--|:--|:--|:--|
+ * | `2026-06-01`       | `2026-05-31` | `2026-W22` | `2026-05` | `2026-Q2` | `2026` |
+ * | `2026-01-01`       | `2025-12-31` | `2026-W01` | `2025-12` | `2025-Q4` | `2025` |
+ * | `2024-12-30`       | `2024-12-29` | `2024-W52` | `2024-12` | `2024-Q4` | `2024` |
+ *
+ * At a UTC session every one of those is the value's own calendar day, which
+ * is why the UTC cells stayed green: the zone decided the answer.
+ *
+ * ## The cells
+ *
+ *  - **sqlite**, every run. A `date` is TEXT there and `strftime` reads it with
+ *    no zone, so this cell is the control the live cells must agree with.
+ *  - **live postgres** / **live mysql**, where `OS_TEST_POSTGRES_URL` /
+ *    `OS_TEST_MYSQL_URL` are provisioned (the `Temporal Conformance (live PG +
+ *    MySQL)` CI job, step "Run driver-sql suite against both live servers"),
+ *    and a named skip (red under `OS_EXPECT_LIVE_DIALECT_MATRIX=1`) otherwise.
+ *    Each runs twice:
+ *     1. **as provisioned** — the session the driver leaves in place. On
+ *        PostgreSQL that is the server's `TimeZone` (`Asia/Shanghai` in CI),
+ *        which is this card's reproduction. On MySQL the driver pins its own
+ *        session to `+00:00` (#3942), so this run cannot see the defect there.
+ *        Both axes are asserted, and the three-way zone skew is asserted first.
+ *     2. **session at +08:00** — a host `pool.afterCreate` sets the session
+ *        zone, which the driver chains after its own hook. This is the run that
+ *        is red-capable on any server, and the only one that is on MySQL. A
+ *        test asserts that the session really is at `+08:00`, so a hook that
+ *        stops taking effect is a red, not a quiet return to UTC.
+ *        Only the `date` axis is asserted here. A host-set MySQL session also
+ *        moves the `datetime` arm, whose `DATETIME(3)` holds the UTC wall
+ *        clock the driver wrote; that arm is outside this card's ruling, which
+ *        keeps it as it is, and it is recorded on the PR instead.
+ *
+ * Every cell checks both doors that render the expression: `aggregate()`'s
+ * GROUP BY, and `dateBucketSql()` — the text the analytics echo prints (#21441)
+ * — run as SQL against the same rows.
+ *
+ * ## Reverse verification
+ *
+ * Measured with all three cells provisioned (PostgreSQL 16.14 at
+ * `Asia/Shanghai`, MySQL 8.0.46 at a global `+08:00`, process
+ * `TZ=America/New_York`), this file beside `sql-driver-temporal-dialect.test.ts`:
+ *
+ * - fix in place: 61 of 61 green;
+ * - `sql-driver.ts` reverted to its pre-fix text: 16 red, 45 green. The red
+ *   ones are the `date` axis at all five granularities on live postgres as
+ *   provisioned, live postgres at `+08:00`, and live mysql at `+08:00` (15),
+ *   plus the no-server pin in the dialect-gating file. Live mysql as
+ *   provisioned stayed green, because the driver's UTC session pin hides the
+ *   defect there. Every `datetime` cell and the sqlite cell stayed green.
+ */
+
+import { afterAll, beforeAll, describe, expect, it } from 'vitest';
+import { SqlDriver, type SqlDriverConfig } from '../src/index.js';
+import {
+  DIALECT_CELLS,
+  assertThreeWayZoneSkew,
+  declareDialectCell,
+  readServerZone,
+  type DialectCell,
+  type DialectId,
+} from './live-dialect-matrix.testkit.js';
+
+const TABLE = 'os21485_bucket';
+
+type Granularity = 'day' | 'week' | 'month' | 'quarter' | 'year';
+type Axis = 'on' | 'at';
+
+const GRANULARITIES: readonly Granularity[] = ['day', 'week', 'month', 'quarter', 'year'];
+
+/**
+ * The granularities each dialect buckets in SQL. Declared rather than read off
+ * the driver, and checked against it below, so the set the tests iterate cannot
+ * shrink without a red. SQLite buckets `week` in memory (#21595 owns that).
+ */
+const BUCKETED_IN_SQL: Record<DialectId, readonly Granularity[]> = {
+  sqlite: ['day', 'month', 'quarter', 'year'],
+  pg: GRANULARITIES,
+  mysql: GRANULARITIES,
+};
+
+type Labels = Record<Granularity, string>;
+const labels = (day: string, week: string, month: string, quarter: string, year: string): Labels =>
+  ({ day, week, month, quarter, year });
+
+/**
+ * Every row, and the label each value buckets under.
+ *
+ * `on` is a calendar day whose midnight at `+08:00` falls on the PREVIOUS UTC
+ * day, at a month, a quarter, a year and an ISO-week boundary. `at` is an
+ * instant whose `+08:00` wall clock is on the NEXT day, across the same
+ * boundaries, so a fix that bucketed a `datetime` by its local day would be
+ * one bucket off too. The last row is the empty bucket.
+ */
+const ROWS: ReadonlyArray<{ id: string; on: [string, Labels] | null; at: [string, Labels] | null }> = [
+  {
+    id: 'r1',
+    on: ['2026-06-01', labels('2026-06-01', '2026-W23', '2026-06', '2026-Q2', '2026')],
+    at: ['2026-05-31T20:00:00.000Z', labels('2026-05-31', '2026-W22', '2026-05', '2026-Q2', '2026')],
+  },
+  {
+    id: 'r2',
+    on: ['2026-04-01', labels('2026-04-01', '2026-W14', '2026-04', '2026-Q2', '2026')],
+    at: ['2026-03-31T18:30:00.000Z', labels('2026-03-31', '2026-W14', '2026-03', '2026-Q1', '2026')],
+  },
+  {
+    id: 'r3',
+    on: ['2026-01-01', labels('2026-01-01', '2026-W01', '2026-01', '2026-Q1', '2026')],
+    at: ['2025-12-31T20:00:00.000Z', labels('2025-12-31', '2026-W01', '2025-12', '2025-Q4', '2025')],
+  },
+  {
+    id: 'r4',
+    on: ['2024-12-30', labels('2024-12-30', '2025-W01', '2024-12', '2024-Q4', '2024')],
+    at: ['2024-12-29T18:00:00.000Z', labels('2024-12-29', '2024-W52', '2024-12', '2024-Q4', '2024')],
+  },
+  { id: 'r5', on: null, at: null },
+];
+
+/** The empty bucket, keyed out of band so it cannot collide with a real label. */
+const EMPTY = '(empty bucket)';
+const labelOf = (v: unknown): string => (v == null ? EMPTY : String(v));
+
+/** label -> row count: what `field` bucketed by `g` must answer. */
+function expectedBuckets(axis: Axis, g: Granularity): [string, number][] {
+  const counts = new Map<string, number>();
+  for (const row of ROWS) {
+    const key = row[axis] ? row[axis]![1][g] : EMPTY;
+    counts.set(key, (counts.get(key) ?? 0) + 1);
+  }
+  return [...counts].sort();
+}
+
+function bucketsOf(rows: readonly Record<string, unknown>[], labelColumn: string): [string, number][] {
+  return rows.map((r): [string, number] => [labelOf(r[labelColumn]), Number(r.n)]).sort();
+}
+
+/** Unwrap a raw result across knex's three dialect shapes. */
+function rowsOf(res: any): Record<string, unknown>[] {
+  if (Array.isArray(res) && Array.isArray(res[0])) return res[0]; // mysql2: [rows, fields]
+  if (Array.isArray(res)) return res; // better-sqlite3
+  return res?.rows ?? []; // pg
+}
+
+/** The statement that sets a session to `+08:00`, per live dialect. */
+const SET_SESSION_ZONE: Partial<Record<DialectId, string>> = {
+  pg: `SET TIME ZONE 'Asia/Shanghai'`,
+  mysql: `SET time_zone = '+08:00'`,
+};
+
+/** The session's own zone, read back through the driver. */
+const READ_SESSION_ZONE: Partial<Record<DialectId, string>> = {
+  pg: `select current_setting('TimeZone') as tz`,
+  mysql: `select @@session.time_zone as tz`,
+};
+
+interface SessionRun {
+  label: string;
+  /** Statement a host `pool.afterCreate` runs on each new connection, if any. */
+  hostSessionSql?: string;
+  /** The axes asserted in this run. */
+  axes: readonly Axis[];
+}
+
+function sessionRuns(cell: DialectCell): SessionRun[] {
+  if (!cell.live) return [{ label: 'in process', axes: ['on', 'at'] }];
+  return [
+    { label: 'session as provisioned', axes: ['on', 'at'] },
+    { label: 'session at +08:00 (host pool.afterCreate)', hostSessionSql: SET_SESSION_ZONE[cell.id], axes: ['on'] },
+  ];
+}
+
+function configFor(cell: DialectCell, run: SessionRun): SqlDriverConfig {
+  const base = cell.config();
+  const sql = run.hostSessionSql;
+  if (!sql) return base;
+  return {
+    ...base,
+    pool: {
+      afterCreate(connection: any, done: (err?: unknown, conn?: unknown) => void) {
+        connection.query(sql, (err: unknown) => done(err, connection));
+      },
+    },
+  };
+}
+
+function measure(cell: DialectCell): void {
+  for (const run of sessionRuns(cell)) {
+    describe(`[#21485] date buckets on ${cell.label}, ${run.label}`, () => {
+      let driver: SqlDriver;
+
+      beforeAll(async () => {
+        driver = new SqlDriver(configFor(cell, run));
+        await driver.execute(`drop table if exists ${TABLE}`).catch(() => {});
+        await driver.initObjects([{ name: TABLE, fields: { on: { type: 'date' }, at: { type: 'datetime' } } }]);
+        for (const row of ROWS) {
+          await driver.create(
+            TABLE,
+            { id: row.id, on: row.on ? row.on[0] : null, at: row.at ? row.at[0] : null },
+            { bypassTenantAudit: true },
+          );
+        }
+      });
+
+      afterAll(async () => {
+        await driver?.execute(`drop table if exists ${TABLE}`).catch(() => {});
+        await driver?.disconnect();
+      });
+
+      if (cell.live && !run.hostSessionSql) {
+        it('runs where the server, the process and UTC are three different zones', async () => {
+          assertThreeWayZoneSkew(cell, await readServerZone(cell, driver));
+        });
+      }
+
+      if (run.hostSessionSql) {
+        it('the session really is at +08:00, so this run can see a zone leak', async () => {
+          const rows = rowsOf(await driver.execute(READ_SESSION_ZONE[cell.id]!));
+          expect(['Asia/Shanghai', '+08:00']).toContain(String(rows[0]?.tz));
+        });
+      }
+
+      it('buckets in SQL exactly the granularities this file iterates', () => {
+        const advertised = Object.entries(driver.supports.queryDateGranularity as Record<string, boolean>)
+          .filter(([, on]) => on)
+          .map(([g]) => g)
+          .sort();
+        expect(advertised).toEqual([...BUCKETED_IN_SQL[cell.id]].sort());
+      });
+
+      for (const axis of run.axes) {
+        const subject = axis === 'on' ? 'a Field.date buckets as its calendar day' : 'a Field.datetime buckets as its UTC instant';
+        it.each(BUCKETED_IN_SQL[cell.id])(`${subject}, by %s: aggregate() and the dateBucketSql echo`, async (g) => {
+          const want = expectedBuckets(axis, g);
+
+          const grouped = await driver.aggregate(TABLE, {
+            groupBy: [{ field: axis, dateGranularity: g }],
+            aggregations: [{ function: 'count', alias: 'n' }],
+          });
+          expect(bucketsOf(grouped as Record<string, unknown>[], axis), 'aggregate()').toEqual(want);
+
+          const expr = driver.dateBucketSql(TABLE, axis, g);
+          expect(expr, 'dateBucketSql renders an expression').toBeTypeOf('string');
+          const echoed = rowsOf(
+            await driver.execute(`select ${expr} as b, count(*) as n from ${TABLE} group by ${expr}`),
+          );
+          expect(bucketsOf(echoed, 'b'), 'the dateBucketSql echo, run').toEqual(want);
+        });
+      }
+    });
+  }
+}
+
+for (const cell of DIALECT_CELLS) {
+  declareDialectCell(cell, 'date-bucket calendar day', measure);
+}
@@ -215,6 +215,35 @@ describe('buildDateBucketExpr dialect gating (#3773)', () => {
     }
   });
 
+  /**
+   * [#21485] The no-server half of the live pins in
+   * `sql-driver-21485-date-bucket-calendar-day.test.ts`, so a regression is red
+   * in every job, including the ones with no PostgreSQL or MySQL attached. A
+   * `Field.date` is a calendar day: its bucket names no zone and converts none.
+   * Each spelling refused below read the session's zone, and on a session east
+   * of UTC moved the day into the previous bucket.
+   *
+   * On PostgreSQL the day must reach `to_char` as a `timestamp`. A bare `date`
+   * there resolves `to_char(timestamptz, text)` through the implicit cast, so a
+   * `timestamptz` is back without the text naming it.
+   */
+  it('Postgres and MySQL bucket a declared Field.date with no zone conversion (#21485)', () => {
+    for (const client of ['pg', 'mysql2']) {
+      const d = makeDriver(client);
+      d.seedDate('t', 'on');
+      for (const g of [...GRANULARITIES, 'week']) {
+        const sql = expr(d, 'on', g, 't')!.sql.toLowerCase();
+        for (const zoned of ['timestamptz', 'time zone', 'convert_tz', 'time_zone']) {
+          expect(sql, `${client} ${g}`).not.toContain(zoned);
+        }
+        if (client === 'pg') expect(sql, `${client} ${g}`).toContain('::date::timestamp,');
+        // The control: the same column with no declaration keeps the UTC-instant arm.
+        expect(expr(d, 'on', g)!.sql.toLowerCase(), `${client} ${g}, undeclared`)
+          .toContain(client === 'pg' ? `at time zone 'utc'` : 'convert_tz(');
+      }
+    }
+  });
+
   it('every emitted expression binds exactly as many identifiers as it references', () => {
     // The quarter expression references the column twice; an epoch-normalised
     // one references it six times. A mismatch here is knex silently shifting