[parser] *: add alter table read only/write support (pingcap#1095)

parser/ast/ddl.go

@@ -2160,6 +2160,7 @@ const (
 	AlterTableRenameTable
 	AlterTableAlterColumn
 	AlterTableLock
+	AlterTableWriteable
 	AlterTableAlgorithm
 	AlterTableRenameIndex
 	AlterTableForce
@@ -2291,6 +2292,7 @@ type AlterTableSpec struct {
 	Visibility      IndexVisibility
 	TiFlashReplica  *TiFlashReplicaSpec
 	PlacementSpecs  []*PlacementSpec
+	Writeable       bool
 }
 
 type TiFlashReplicaSpec struct {
@@ -2497,6 +2499,13 @@ func (n *AlterTableSpec) Restore(ctx *format.RestoreCtx) error {
 		ctx.WriteKeyWord("LOCK ")
 		ctx.WritePlain("= ")
 		ctx.WriteKeyWord(n.LockType.String())
+	case AlterTableWriteable:
+		ctx.WriteKeyWord("READ ")
+		if n.Writeable {
+			ctx.WriteKeyWord("WRITE")
+		} else {
+			ctx.WriteKeyWord("ONLY")
+		}
 	case AlterTableOrderByColumns:
 		ctx.WriteKeyWord("ORDER BY ")
 		for i, alterOrderItem := range n.OrderByList {

parser/model/model.go

@@ -386,6 +386,9 @@ const (
 	TableLockRead
 	// TableLockReadLocal is not supported.
 	TableLockReadLocal
+	// TableLockReadOnly is used to set a table into read-only status,
+	// when the session exits, it will not release its lock automatically.
+	TableLockReadOnly
 	// TableLockWrite means only the session with this lock has write/read permission.
 	// Only the session that holds the lock can access the table. No other session can access it until the lock is released.
 	TableLockWrite
@@ -401,6 +404,8 @@ func (t TableLockType) String() string {
 		return "READ"
 	case TableLockReadLocal:
 		return "READ LOCAL"
+	case TableLockReadOnly:
+		return "READ ONLY"
 	case TableLockWriteLocal:
 		return "WRITE LOCAL"
 	case TableLockWrite: