ddl, planner, types: add M>=D checking for decimal column definition …

…with default value (#21845)

ddl/db_integration_test.go

@@ -2679,3 +2679,11 @@ func (s *testIntegrationSuite3) TestIssue22028(c *C) {
 	_, err = tk.Exec("ALTER TABLE t MODIFY COLUMN a DOUBLE(0,0);")
 	c.Assert(err.Error(), Equals, "[types:1439]Display width out of range for column 'a' (max = 255)")
 }
+
+func (s *testIntegrationSuite3) TestIssue21835(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t;")
+	_, err := tk.Exec("create table t( col decimal(1,2) not null default 0);")
+	c.Assert(err.Error(), Equals, "[types:1427]For float(M,D), double(M,D) or decimal(M,D), M must be >= D (column 'col').")
+}

planner/core/preprocess.go

@@ -973,6 +973,9 @@ func checkColumn(colDef *ast.ColumnDef) error {
 			if tp.Flen > mysql.MaxFloatingTypeWidth || tp.Flen == 0 {
 				return types.ErrTooBigDisplayWidth.GenWithStackByArgs(colDef.Name.Name.O, mysql.MaxFloatingTypeWidth)
 			}
+			if tp.Flen < tp.Decimal {
+				return types.ErrMBiggerThanD.GenWithStackByArgs(colDef.Name.Name.O)
+			}
 		}
 	case mysql.TypeSet:
 		if len(tp.Elems) > mysql.MaxTypeSetMembers {
@@ -993,6 +996,9 @@ func checkColumn(colDef *ast.ColumnDef) error {
 			return types.ErrTooBigPrecision.GenWithStackByArgs(tp.Flen, colDef.Name.Name.O, mysql.MaxDecimalWidth)
 		}
 
+		if tp.Flen < tp.Decimal {
+			return types.ErrMBiggerThanD.GenWithStackByArgs(colDef.Name.Name.O)
+		}
 		// If decimal and flen all equals 0, just set flen to default value.
 		if tp.Decimal == 0 && tp.Flen == 0 {
 			defaultFlen, _ := mysql.GetDefaultFieldLengthAndDecimal(mysql.TypeNewDecimal)