chore: import upstream snapshot with attribution

server/ast/index_elem.go

@@ -0,0 +1,80 @@
+// 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/sirupsen/logrus"
+
+	"github.com/dolthub/doltgresql/postgres/parser/sem/tree"
+)
+
+// nodeIndexElemList converts a tree.IndexElemList to a slice of vitess.IndexField.
+func nodeIndexElemList(ctx *Context, node tree.IndexElemList) ([]*vitess.IndexField, error) {
+	vitessIndexColumns := make([]*vitess.IndexField, 0, len(node))
+	for _, inputColumn := range node {
+		if inputColumn.Collation != "" {
+			logrus.Warn("index attribute collation is not yet supported, ignoring")
+		}
+		if inputColumn.OpClass != nil {
+			logrus.Warn("index attribute operator class is not yet supported, ignoring")
+		}
+		if inputColumn.ExcludeOp != nil {
+			return nil, errors.Errorf("index attribute exclude operator is not yet supported")
+		}
+
+		switch inputColumn.Direction {
+		case tree.DefaultDirection:
+			// Defaults to ASC
+		case tree.Ascending:
+			// The only default supported in GMS for now
+		case tree.Descending:
+			logrus.Warn("descending indexes are not yet supported, ignoring sort order")
+		default:
+			return nil, errors.Errorf("unknown index sorting direction encountered")
+		}
+
+		switch inputColumn.NullsOrder {
+		case tree.DefaultNullsOrder:
+			// TODO: the default NULL order is reversed compared to MySQL, so the default is technically always wrong.
+			//       To prevent choking on every index, we allow this to proceed (even with incorrect results) for now.
+		case tree.NullsFirst:
+			// The only form supported in GMS for now
+		case tree.NullsLast:
+			return nil, errors.Errorf("NULLS LAST for indexes is not yet supported")
+		default:
+			return nil, errors.Errorf("unknown NULL ordering for index")
+		}
+
+		var expr vitess.Expr
+		if inputColumn.Expr != nil {
+			var err error
+			expr, err = nodeExpr(ctx, inputColumn.Expr)
+			if err != nil {
+				return nil, err
+			}
+		}
+
+		vitessIndexColumns = append(vitessIndexColumns, &vitess.IndexField{
+			Column:     vitess.NewColIdent(string(inputColumn.Column)),
+			Order:      vitess.AscScr,
+			Expression: expr,
+		})
+	}
+
+	return vitessIndexColumns, nil
+}