Round the Postgres clock down to the second, like SQLite

limit/store_postgres.go

@@ -6,15 +6,16 @@ import (
 	"heckel.io/ntfy/v2/db"
 )
 
-// Timestamps come from the database clock, never from a node's (see Store). The upsert is one
+// Timestamps come from the database clock, never from a node's (see Store), rounded down to the
+// second like SQLite's. The upsert is one
 // fixed statement per chunk (unnest), because SQL built per call bloats pgx's statement cache.
 // Same period: add; a newer one: replace; an older one (a leftover): add to the stored period.
 const (
-	postgresSelectClockQuery = `SELECT EXTRACT(EPOCH FROM now())::BIGINT`
+	postgresSelectClockQuery = `SELECT FLOOR(EXTRACT(EPOCH FROM now()))::BIGINT`
 	postgresSelectSinceQuery = `SELECT key, period_start, messages, emails, calls FROM usage WHERE updated_at >= $1`
 	postgresUpsertQuery      = `
 		INSERT INTO usage AS u (key, period_start, messages, emails, calls, updated_at)
-		SELECT key, ps, m, e, c, EXTRACT(EPOCH FROM now())::BIGINT
+		SELECT key, ps, m, e, c, FLOOR(EXTRACT(EPOCH FROM now()))::BIGINT
 		FROM unnest($1::TEXT[], $2::BIGINT[], $3::BIGINT[], $4::BIGINT[], $5::BIGINT[]) AS d(key, ps, m, e, c)
 		ON CONFLICT (key) DO UPDATE SET
 			messages = CASE WHEN u.period_start >= EXCLUDED.period_start THEN u.messages + EXCLUDED.messages ELSE EXCLUDED.messages END,

limit/store_test.go

@@ -212,3 +212,29 @@ func keysOf(rows map[string]usageRow) []string {
 	slices.Sort(keys)
 	return keys
 }
+
+func TestStore_ClockTruncatesToTheSecond(t *testing.T) {
+	// Database time is whole seconds, rounded down on both dialects, for the clock and for
+	// updated_at alike (the test database runs on this host's clock)
+	forEachBackend(t, func(t *testing.T, newStore func() *Store) {
+		s := newStore()
+		ctx := context.Background()
+		for i := 0; i < 20; i++ {
+			dbNow, err := s.clock(ctx)
+			require.Nil(t, err)
+			require.LessOrEqual(t, dbNow, time.Now().Unix())
+			_, err = s.write(ctx, []usageRow{
+				{
+					key:         "k",
+					periodStart: 1,
+					counts:      [numDaily]int64{1, 0, 0},
+				},
+			})
+			require.Nil(t, err)
+			var updatedAt int64
+			require.Nil(t, s.db.QueryRow(`SELECT updated_at FROM usage WHERE key = 'k'`).Scan(&updatedAt))
+			require.LessOrEqual(t, updatedAt, time.Now().Unix())
+			time.Sleep(37 * time.Millisecond)
+		}
+	})
+}