message: Throw exception for recursive CTEs using UNION semantics for now
diff: @@ -68,6 +68,11 @@ void Transformer::TransformCTE(PGWithClause *de_with_clause, SelectStatement &se
  unique_ptr<QueryNode> Transformer::TransformRecursiveCTE(PGCommonTableExpr *cte) {
  auto stmt = (PGSelectStmt *)cte->ctequery;
  +
  + if(!stmt->all) {
  + throw Exception("UNION semantics for recursive CTEs is not implemented.");
  + }
  +
  unique_ptr<QueryNode> node;
  switch (stmt->op) {
  case PG_SETOP_UNION:
  @@ -79,6 +84,7 @@ unique_ptr<QueryNode> Transformer::TransformRecursiveCTE(PGCommonTableExpr *cte)
  result->union_all = stmt->all;
  result->left = TransformSelectNode(stmt->larg);
  result->right = TransformSelectNode(stmt->rarg);
  +
  if (!result->left || !result->right) {
  throw Exception("Failed to transform setop children.");
  }
  