ddl:support alter table comment

ast/ddl.go

@@ -745,6 +745,7 @@ type AlterTableSpec struct {
 	OldColumnName *ColumnName
 	Position      *ColumnPosition
 	LockType      LockType
+	Comment       string
 }
 
 // Accept implements Node Accept interface.

ddl/ddl_api.go

@@ -934,6 +934,9 @@ func (d *ddl) AlterTable(ctx sessionctx.Context, ident ast.Ident, specs []*ast.A
 					err = d.ShardRowID(ctx, ident, opt.UintValue)
 				case ast.TableOptionAutoIncrement:
 					err = d.RebaseAutoID(ctx, ident, int64(opt.UintValue))
+				case ast.TableOptionComment:
+					spec.Comment = opt.StrValue
+					err = d.AlterTableComment(ctx, ident, spec)
 				}
 				if err != nil {
 					return errors.Trace(err)
@@ -1448,6 +1451,32 @@ func (d *ddl) AlterColumn(ctx sessionctx.Context, ident ast.Ident, spec *ast.Alt
 	return errors.Trace(err)
 }
 
+// AlterTableComment updates the table comment information.
+func (d *ddl) AlterTableComment(ctx sessionctx.Context, ident ast.Ident, spec *ast.AlterTableSpec) error {
+	is := d.infoHandle.Get()
+	schema, ok := is.SchemaByName(ident.Schema)
+	if !ok {
+		return infoschema.ErrDatabaseNotExists.GenByArgs(ident.Schema)
+	}
+
+	tb, err := is.TableByName(ident.Schema, ident.Name)
+	if err != nil {
+		return errors.Trace(infoschema.ErrTableNotExists.GenByArgs(ident.Schema, ident.Name))
+	}
+
+	job := &model.Job{
+		SchemaID:   schema.ID,
+		TableID:    tb.Meta().ID,
+		Type:       model.ActionModifyTableComment,
+		BinlogInfo: &model.HistoryInfo{},
+		Args:       []interface{}{spec.Comment},
+	}
+
+	err = d.doDDLJob(ctx, job)
+	err = d.callHookOnChanged(err)
+	return errors.Trace(err)
+}
+
 // DropTable will proceed even if some table in the list does not exists.
 func (d *ddl) DropTable(ctx sessionctx.Context, ti ast.Ident) (err error) {
 	is := d.GetInformationSchema()

ddl/ddl_db_test.go

@@ -167,6 +167,9 @@ func (s *testDBSuite) TestMySQLErrorCode(c *C) {
 	s.testErrorCode(c, sql, tmysql.ErrDupFieldName)
 	sql = "alter table test_error_code_succ add column aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa int"
 	s.testErrorCode(c, sql, tmysql.ErrTooLongIdent)
+	sql = "alter table test_comment comment 'test comment'"
+	s.testErrorCode(c, sql, tmysql.ErrNoSuchTable)
+
 	// drop column
 	sql = "alter table test_error_code_succ drop c_not_exist"
 	s.testErrorCode(c, sql, tmysql.ErrCantDropFieldOrKey)

ddl/ddl_worker.go

@@ -329,6 +329,8 @@ func (d *ddl) runDDLJob(t *meta.Meta, job *model.Job) (ver int64, err error) {
 		ver, err = d.onSetDefaultValue(t, job)
 	case model.ActionShardRowID:
 		ver, err = d.onShardRowID(t, job)
+	case model.ActionModifyTableComment:
+		ver, err = d.onModifyTableComment(t, job)
 	default:
 		// Invalid job, cancel it.
 		job.State = model.JobStateCancelled

ddl/table.go

@@ -335,6 +335,27 @@ func (d *ddl) onRenameTable(t *meta.Meta, job *model.Job) (ver int64, _ error) {
 	return ver, nil
 }
 
+func (d *ddl) onModifyTableComment(t *meta.Meta, job *model.Job) (ver int64, _ error) {
+	var comment string
+	if err := job.DecodeArgs(&comment); err != nil {
+		job.State = model.JobStateCancelled
+		return ver, errors.Trace(err)
+	}
+
+	tblInfo, err := getTableInfo(t, job, job.SchemaID)
+	if err != nil {
+		return ver, errors.Trace(err)
+	}
+
+	tblInfo.Comment = comment
+	ver, err = updateVersionAndTableInfo(t, job, tblInfo, true)
+	if err != nil {
+		return ver, errors.Trace(err)
+	}
+	job.FinishTableJob(model.JobStateDone, model.StatePublic, ver, tblInfo)
+	return ver, nil
+}
+
 func checkTableNotExists(t *meta.Meta, job *model.Job, schemaID int64, tableName string) error {
 	// Check this table's database.
 	tables, err := t.ListTables(schemaID)

executor/executor_test.go

@@ -2155,6 +2155,19 @@ func (s *testContextOptionSuite) TestAddIndexPriority(c *C) {
 	store.Close()
 }
 
+func (s *testContextOptionSuite) TestAlterTableComment(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t_1")
+	tk.MustExec("create table t_1 (c1 int, c2 int, c3 int default 1, index (c1)) comment = 'test table';")
+	tk.MustExec("alter table `t_1` comment 'this is table comment';")
+	result := tk.MustQuery("select table_comment from information_schema.tables where table_name = 't_1';")
+	result.Check(testkit.Rows("this is table comment"))
+	tk.MustExec("alter table `t_1` comment 'table t comment';")
+	result = tk.MustQuery("select table_comment from information_schema.tables where table_name = 't_1';")
+	result.Check(testkit.Rows("table t comment"))
+}
+
 func (s *testContextOptionSuite) TestCoprocessorPriority(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")

model/ddl.go

@@ -28,42 +28,44 @@ type ActionType byte
 
 // List DDL actions.
 const (
-	ActionNone            ActionType = 0
-	ActionCreateSchema    ActionType = 1
-	ActionDropSchema      ActionType = 2
-	ActionCreateTable     ActionType = 3
-	ActionDropTable       ActionType = 4
-	ActionAddColumn       ActionType = 5
-	ActionDropColumn      ActionType = 6
-	ActionAddIndex        ActionType = 7
-	ActionDropIndex       ActionType = 8
-	ActionAddForeignKey   ActionType = 9
-	ActionDropForeignKey  ActionType = 10
-	ActionTruncateTable   ActionType = 11
-	ActionModifyColumn    ActionType = 12
-	ActionRebaseAutoID    ActionType = 13
-	ActionRenameTable     ActionType = 14
-	ActionSetDefaultValue ActionType = 15
-	ActionShardRowID      ActionType = 16
+	ActionNone               ActionType = 0
+	ActionCreateSchema       ActionType = 1
+	ActionDropSchema         ActionType = 2
+	ActionCreateTable        ActionType = 3
+	ActionDropTable          ActionType = 4
+	ActionAddColumn          ActionType = 5
+	ActionDropColumn         ActionType = 6
+	ActionAddIndex           ActionType = 7
+	ActionDropIndex          ActionType = 8
+	ActionAddForeignKey      ActionType = 9
+	ActionDropForeignKey     ActionType = 10
+	ActionTruncateTable      ActionType = 11
+	ActionModifyColumn       ActionType = 12
+	ActionRebaseAutoID       ActionType = 13
+	ActionRenameTable        ActionType = 14
+	ActionSetDefaultValue    ActionType = 15
+	ActionShardRowID         ActionType = 16
+	ActionModifyTableComment ActionType = 17
 )
 
 var actionMap = map[ActionType]string{
-	ActionCreateSchema:    "create schema",
-	ActionDropSchema:      "drop schema",
-	ActionCreateTable:     "create table",
-	ActionDropTable:       "drop table",
-	ActionAddColumn:       "add column",
-	ActionDropColumn:      "drop column",
-	ActionAddIndex:        "add index",
-	ActionDropIndex:       "drop index",
-	ActionAddForeignKey:   "add foreign key",
-	ActionDropForeignKey:  "drop foreign key",
-	ActionTruncateTable:   "truncate table",
-	ActionModifyColumn:    "modify column",
-	ActionRebaseAutoID:    "rebase auto_increment ID",
-	ActionRenameTable:     "rename table",
-	ActionSetDefaultValue: "set default value",
-	ActionShardRowID:      "shard row ID",
+	ActionCreateSchema:       "create schema",
+	ActionDropSchema:         "drop schema",
+	ActionCreateTable:        "create table",
+	ActionDropTable:          "drop table",
+	ActionAddColumn:          "add column",
+	ActionDropColumn:         "drop column",
+	ActionAddIndex:           "add index",
+	ActionDropIndex:          "drop index",
+	ActionAddForeignKey:      "add foreign key",
+	ActionDropForeignKey:     "drop foreign key",
+	ActionTruncateTable:      "truncate table",
+	ActionModifyColumn:       "modify column",
+	ActionRebaseAutoID:       "rebase auto_increment ID",
+	ActionRenameTable:        "rename table",
+	ActionSetDefaultValue:    "set default value",
+	ActionShardRowID:         "shard row ID",
+	ActionModifyTableComment: "modify table comment",
 }
 
 // String return current ddl action in string