chore: import upstream snapshot with attribution

server/ast/union_clause.go

@@ -0,0 +1,69 @@
+// Copyright 2023 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package ast
+
+import (
+	"github.com/cockroachdb/errors"
+
+	vitess "github.com/dolthub/vitess/go/vt/sqlparser"
+
+	"github.com/dolthub/doltgresql/postgres/parser/sem/tree"
+)
+
+// nodeUnionClause handles tree.UnionClause nodes.
+func nodeUnionClause(ctx *Context, node *tree.UnionClause) (*vitess.SetOp, error) {
+	if node == nil {
+		return nil, nil
+	}
+	left, err := nodeSelect(ctx, node.Left)
+	if err != nil {
+		return nil, err
+	}
+	right, err := nodeSelect(ctx, node.Right)
+	if err != nil {
+		return nil, err
+	}
+	var unionType string
+	switch node.Type {
+	case tree.UnionOp:
+		if node.All {
+			unionType = vitess.UnionAllStr
+		} else {
+			unionType = vitess.UnionStr
+		}
+	case tree.IntersectOp:
+		if node.All {
+			unionType = vitess.IntersectAllStr
+		} else {
+			unionType = vitess.IntersectStr
+		}
+	case tree.ExceptOp:
+		if node.All {
+			unionType = vitess.ExceptAllStr
+		} else {
+			unionType = vitess.ExceptStr
+		}
+	default:
+		return nil, errors.Errorf("unknown type of UNION operator: `%s`", node.Type.String())
+	}
+
+	// TODO next: the types here are incorrect for parenthetical table statements
+	// Need to compare with the vitess result to see what the correct type is here
+	return &vitess.SetOp{
+		Type:  unionType,
+		Left:  left,
+		Right: right,
+	}, nil
+}