ddl: forbidden changing decimal to int (#19645) (#19682)

pingcap · Sep 3, 2020 · df761ba · df761ba
1 parent 5999f65
commit df761ba
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Showing 2 changed files with 6 additions and 0 deletions.
diff --git a/ddl/column_test.go b/ddl/column_test.go
@@ -948,6 +948,9 @@ func (s *testColumnSuite) TestModifyColumn(c *C) {
 		{"decimal(2,1)", "decimal(3,2)", errUnsupportedModifyColumn.GenWithStackByArgs("can't change decimal column precision")},
 		{"decimal(2,1)", "decimal(2,2)", errUnsupportedModifyColumn.GenWithStackByArgs("can't change decimal column precision")},
 		{"decimal(2,1)", "decimal(2,1)", nil},
+		{"decimal(2,1)", "int", errUnsupportedModifyColumn.GenWithStackByArgs("type int(11) not match origin decimal(2,1)")},
+		{"decimal", "int", errUnsupportedModifyColumn.GenWithStackByArgs("type int(11) not match origin decimal(11,0)")},
+		{"decimal(2,1)", "bigint", errUnsupportedModifyColumn.GenWithStackByArgs("type bigint(20) not match origin decimal(2,1)")},
 	}
 	for _, tt := range tests {
 		ftA := s.colDefStrToFieldType(c, tt.origin)

diff --git a/ddl/ddl_api.go b/ddl/ddl_api.go
@@ -2750,6 +2750,9 @@ func checkModifyTypes(origin *types.FieldType, to *types.FieldType, needRewriteC
 			}
 		}
 	case mysql.TypeNewDecimal:
+		if origin.Tp != to.Tp {
+			return errUnsupportedModifyColumn.GenWithStackByArgs(unsupportedMsg)
+		}
 		// The root cause is modifying decimal precision needs to rewrite binary representation of that decimal.
 		if to.Flen != origin.Flen || to.Decimal != origin.Decimal {
 			return errUnsupportedModifyColumn.GenWithStackByArgs("can't change decimal column precision")