chore: import upstream snapshot with attribution

server/ast/group_by.go

@@ -0,0 +1,52 @@
+// 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/dolthub/go-mysql-server/sql/expression"
+	vitess "github.com/dolthub/vitess/go/vt/sqlparser"
+
+	pgexprs "github.com/dolthub/doltgresql/server/expression"
+
+	"github.com/dolthub/doltgresql/postgres/parser/sem/tree"
+)
+
+// nodeGroupBy handles tree.GroupBy nodes.
+func nodeGroupBy(ctx *Context, node tree.GroupBy) (vitess.GroupBy, error) {
+	if len(node) == 0 {
+		return nil, nil
+	}
+
+	groupBys := make(vitess.GroupBy, len(node))
+	var err error
+	for i, expr := range node {
+		groupBys[i], err = nodeExpr(ctx, expr)
+		if err != nil {
+			return nil, err
+		}
+
+		// GMS order by is hardcoded to expect vitess.SQLVal for expressions such as `ORDER BY 1`.
+		// In addition, there is the requirement that columns in the order by also need to be referenced somewhere in
+		// the query, which is not a requirement for Postgres. Whenever we add that functionality, we also need to
+		// remove the dependency on vitess.SQLVal. For now, we'll just convert our literals to a vitess.SQLVal.
+		if injectedExpr, ok := groupBys[i].(vitess.InjectedExpr); ok {
+			if literal, ok := injectedExpr.Expression.(*expression.Literal); ok {
+				groupBys[i] = pgexprs.ToVitessLiteral(literal)
+			}
+		}
+	}
+
+	return groupBys, nil
+}