ddl: add not null flag for auto_increment column (#30477)

ddl/ddl_api.go

@@ -774,6 +774,7 @@ func columnDefToCol(ctx sessionctx.Context, offset int, colDef *ast.ColumnDef, o
 				hasNullFlag = true
 			case ast.ColumnOptionAutoIncrement:
 				col.Flag |= mysql.AutoIncrementFlag
+				col.Flag |= mysql.NotNullFlag
 			case ast.ColumnOptionPrimaryKey:
 				// Check PriKeyFlag first to avoid extra duplicate constraints.
 				if col.Flag&mysql.PriKeyFlag == 0 {

ddl/serial_test.go

@@ -1652,6 +1652,7 @@ func (s *testIntegrationSuite7) TestInvisibleIndex(c *C) {
 	// Implicit primary key cannot be invisible index
 	// Create a implicit primary key
 	tk.MustGetErrCode("create table t2(a int not null, unique (a) invisible)", errno.ErrPKIndexCantBeInvisible)
+	tk.MustGetErrCode("create table t2(a int auto_increment, unique key (a) invisible);", errno.ErrPKIndexCantBeInvisible)
 	// Column `a` become implicit primary key after DDL statement on itself
 	tk.MustExec("create table t2(a int not null)")
 	tk.MustGetErrCode("alter table t2 add unique (a) invisible", errno.ErrPKIndexCantBeInvisible)