[parser] parser: fix alter_stmt order by syntax (#526)

parser/Makefile

@@ -33,7 +33,7 @@ bin/goyacc: goyacc/main.go
 
 fmt:
 	@echo "gofmt (simplify)"
-	@ gofmt -s -l -w . 2>&1 | awk '{print} END{if(NR>0) {exit 1}}'
+	@gofmt -s -l -w . 2>&1 | awk '{print} END{if(NR>0) {exit 1}}'
 
 clean:
 	go clean -i ./...

parser/ast/ddl.go

@@ -1920,6 +1920,7 @@ const (
 	AlterTableDiscardTablespace
 	AlterTableIndexInvisible
 	// TODO: Add more actions
+	AlterTableOrderByColumns
 )
 
 // LockType is the type for AlterTableSpec.
@@ -1996,6 +1997,7 @@ type AlterTableSpec struct {
 	Name            string
 	Constraint      *Constraint
 	Options         []*TableOption
+	OrderByList     []*AlterOrderItem
 	NewTable        *TableName
 	NewColumns      []*ColumnDef
 	OldColumnName   *ColumnName
@@ -2014,6 +2016,24 @@ type AlterTableSpec struct {
 	Visibility      IndexVisibility
 }
 
+// AlterOrderItem represents an item in order by at alter table stmt.
+type AlterOrderItem struct {
+	node
+	Column *ColumnName
+	Desc   bool
+}
+
+// Restore implements Node interface.
+func (n *AlterOrderItem) Restore(ctx *RestoreCtx) error {
+	if err := n.Column.Restore(ctx); err != nil {
+		return errors.Annotate(err, "An error occurred while restore AlterOrderItem.Column")
+	}
+	if n.Desc {
+		ctx.WriteKeyWord(" DESC")
+	}
+	return nil
+}
+
 // Restore implements Node interface.
 func (n *AlterTableSpec) Restore(ctx *RestoreCtx) error {
 	switch n.Tp {
@@ -2163,6 +2183,16 @@ func (n *AlterTableSpec) Restore(ctx *RestoreCtx) error {
 		ctx.WriteKeyWord("LOCK ")
 		ctx.WritePlain("= ")
 		ctx.WriteKeyWord(n.LockType.String())
+	case AlterTableOrderByColumns:
+		ctx.WriteKeyWord("ORDER BY ")
+		for i, alterOrderItem := range n.OrderByList {
+			if i != 0 {
+				ctx.WritePlain(",")
+			}
+			if err := alterOrderItem.Restore(ctx); err != nil {
+				return errors.Annotatef(err, "An error occurred while restore AlterTableSpec.OrderByList[%d]", i)
+			}
+		}
 	case AlterTableAlgorithm:
 		ctx.WriteKeyWord("ALGORITHM ")
 		ctx.WritePlain("= ")