ddl: reorganize in conversion between double and float

Signed-off-by: unconsolable <chenzhipeng2012@gmail.com>
pingcap · Jan 7, 2022 · 26633cc · 26633cc
1 parent 40c0567
commit 26633cc
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Showing 2 changed files with 17 additions and 5 deletions.
diff --git a/ddl/column.go b/ddl/column.go
@@ -736,11 +736,7 @@ func needChangeColumnData(oldCol, newCol *model.ColumnInfo) bool {
 		case mysql.TypeTiny, mysql.TypeShort, mysql.TypeInt24, mysql.TypeLong, mysql.TypeLonglong:
 			return needTruncationOrToggleSignForInteger()
 		}
-	case mysql.TypeFloat, mysql.TypeDouble:
-		switch newCol.Tp {
-		case mysql.TypeFloat, mysql.TypeDouble:
-			return needTruncationOrToggleSign()
-		}
+		// conversion between float and double needs reorganization, see issue #31372
 	}
 
 	return true

diff --git a/ddl/column_type_change_test.go b/ddl/column_type_change_test.go
@@ -2352,3 +2352,19 @@ func (s *testColumnTypeChangeSuite) TestChangeNullValueFromOtherTypeToTimestamp(
 	_, err = tk.Exec("insert into t values(null)")
 	c.Assert(err.Error(), Equals, "[table:1048]Column 'a' cannot be null")
 }
+
+func (s *testColumnTypeChangeSuite) TestColumnTypeChangeFromFloatToDouble(c *C) {
+	// issue #31372
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+
+	prepare := func() {
+		tk.MustExec("drop table if exists t;")
+		tk.MustExec("create table t (a float(6,2));")
+		tk.MustExec("insert into t values (36.4), (24.1);")
+	}
+
+	prepare()
+	tk.MustExec("alter table t modify a double(6,2)")
+	tk.MustQuery("select a from t;").Check(testkit.Rows("36.4", "24.1"))
+}