chore: import upstream snapshot with attribution

server/ast/begin_transaction.go

@@ -0,0 +1,56 @@
+// 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"
+)
+
+// nodeBeginTransaction handles *tree.BeginTransaction nodes.
+func nodeBeginTransaction(ctx *Context, node *tree.BeginTransaction) (*vitess.Begin, error) {
+	if node == nil {
+		return nil, nil
+	}
+	if node.Modes.Isolation != tree.UnspecifiedIsolation {
+		return nil, errors.Errorf("isolation levels are not yet supported")
+	}
+	if node.Modes.UserPriority != tree.UnspecifiedUserPriority {
+		return nil, errors.Errorf("user priority is not yet supported")
+	}
+	if node.Modes.AsOf.Expr != nil {
+		return nil, errors.Errorf("AS OF is not yet supported")
+	}
+	if node.Modes.Deferrable != tree.UnspecifiedDeferrableMode {
+		return nil, errors.Errorf("deferrability is not yet supported")
+	}
+	var characteristic string
+	switch node.Modes.ReadWriteMode {
+	case tree.UnspecifiedReadWriteMode:
+		characteristic = vitess.TxReadWrite
+	case tree.ReadOnly:
+		characteristic = vitess.TxReadOnly
+	case tree.ReadWrite:
+		characteristic = vitess.TxReadWrite
+	default:
+		return nil, errors.Errorf("unknown READ/WRITE setting")
+	}
+	return &vitess.Begin{
+		TransactionCharacteristic: characteristic,
+	}, nil
+}