refactor(db): move the heard-IATA lookup into sqlc

db/sqlc/mock/querier.go

@@ -1316,6 +1316,21 @@ func (mr *MockQuerierMockRecorder) ListDirtyRollupHours(ctx, limit any) *gomock.
 	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ListDirtyRollupHours", reflect.TypeOf((*MockQuerier)(nil).ListDirtyRollupHours), ctx, limit)
 }
 
+// ListHeardIATAs mocks base method.
+func (m *MockQuerier) ListHeardIATAs(ctx context.Context) ([]string, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "ListHeardIATAs", ctx)
+	ret0, _ := ret[0].([]string)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// ListHeardIATAs indicates an expected call of ListHeardIATAs.
+func (mr *MockQuerierMockRecorder) ListHeardIATAs(ctx any) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "ListHeardIATAs", reflect.TypeOf((*MockQuerier)(nil).ListHeardIATAs), ctx)
+}
+
 // ListIATAs mocks base method.
 func (m *MockQuerier) ListIATAs(ctx context.Context) ([]db.IataCode, error) {
 	m.ctrl.T.Helper()

db/sqlc/querier.go

@@ -200,6 +200,7 @@ type Querier interface {
 	// Only complete hours whose raw rows are still intact can be re-rolled. Queued missing hours
 	// wait: their first roll consumes the entry only if the entry predates its snapshot.
 	ListDirtyRollupHours(ctx context.Context, limit int32) ([]pgtype.Timestamptz, error)
+	ListHeardIATAs(ctx context.Context) ([]string, error)
 	ListIATAs(ctx context.Context) ([]IataCode, error)
 	// Only one branch runs. Keep the IATA range ordered by the composite index:
 	// generic plans can otherwise prefer scanning the global timestamp index.

db/sqlc/queries.sql.go

@@ -2912,6 +2912,30 @@ func (q *Queries) ListChannelsAfter(ctx context.Context, arg ListChannelsAfterPa
 	return items, nil
 }
 
+const listHeardIATAs = `-- name: ListHeardIATAs :many
+SELECT DISTINCT last_iata::text AS iata FROM observers WHERE last_iata IS NOT NULL ORDER BY 1
+`
+
+func (q *Queries) ListHeardIATAs(ctx context.Context) ([]string, error) {
+	rows, err := q.db.Query(ctx, listHeardIATAs)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	items := []string{}
+	for rows.Next() {
+		var iata string
+		if err := rows.Scan(&iata); err != nil {
+			return nil, err
+		}
+		items = append(items, iata)
+	}
+	if err := rows.Err(); err != nil {
+		return nil, err
+	}
+	return items, nil
+}
+
 const listIATAs = `-- name: ListIATAs :many
 SELECT iata, display_name, approx_lat, approx_lng, added_at, border FROM iata_codes ORDER BY iata
 `