chore: import upstream snapshot with attribution

server/ast/drop_index.go

@@ -0,0 +1,70 @@
+// 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"
+)
+
+// nodeDropIndex handles *tree.DropIndex nodes.
+func nodeDropIndex(ctx *Context, node *tree.DropIndex) (*vitess.AlterTable, error) {
+	if node == nil || len(node.IndexList) == 0 {
+		return nil, nil
+	}
+	switch node.DropBehavior {
+	case tree.DropDefault:
+		// Default behavior, nothing to do
+	case tree.DropRestrict:
+		return nil, errors.Errorf("RESTRICT is not yet supported")
+	case tree.DropCascade:
+		return nil, errors.Errorf("CASCADE is not yet supported")
+	}
+	if len(node.IndexList) > 1 {
+		return nil, errors.Errorf("multi-index dropping is not yet supported")
+	}
+	if node.Concurrently {
+		return nil, errors.Errorf("concurrent indexes are not yet supported")
+	}
+	var tableName vitess.TableName
+	ddls := make([]*vitess.DDL, len(node.IndexList))
+	for i, index := range node.IndexList {
+		newTableName, err := nodeTableName(ctx, &index.Table)
+		if err != nil {
+			return nil, err
+		}
+		if !tableName.Name.IsEmpty() && tableName.String() != newTableName.String() {
+			return nil, errors.Errorf("only dropping indexes from the same table is currently supported")
+		}
+		tableName = newTableName
+		ddls[i] = &vitess.DDL{
+			Action:   vitess.AlterStr,
+			Table:    tableName,
+			IfExists: node.IfExists,
+			IndexSpec: &vitess.IndexSpec{
+				Action:   vitess.DropStr,
+				FromName: vitess.NewColIdent(string(index.Index)),
+				ToName:   vitess.NewColIdent(string(index.Index)),
+			},
+		}
+	}
+	return &vitess.AlterTable{
+		Table:      tableName,
+		Statements: ddls,
+	}, nil
+}