From 2a758efe3e5899b045f0c1c39bd288c7d5e41f70 Mon Sep 17 00:00:00 2001
From: ti-srebot <66930949+ti-srebot@users.noreply.github.com>
Date: Sat, 3 Oct 2020 21:35:39 +0800
Subject: [PATCH] ddl: check constraint when alter enum/set type column
 (#19806) (#20046)

---
 ddl/ddl_api.go                 | 18 ++++++++++++++----
 expression/integration_test.go | 20 +++++++++++++++++++-
 2 files changed, 33 insertions(+), 5 deletions(-)

diff --git a/ddl/ddl_api.go b/ddl/ddl_api.go
index 0da443b5c99ce..2c0cdd2411f5b 100644
--- a/ddl/ddl_api.go
+++ b/ddl/ddl_api.go
@@ -2734,19 +2734,25 @@ func CheckModifyTypeCompatible(origin *types.FieldType, to *types.FieldType) err
 		default:
 			return errUnsupportedModifyColumn.GenWithStackByArgs(unsupportedMsg)
 		}
-	case mysql.TypeEnum:
+	case mysql.TypeEnum, mysql.TypeSet:
+		var typeVar string
+		if origin.Tp == mysql.TypeEnum {
+			typeVar = "enum"
+		} else {
+			typeVar = "set"
+		}
 		if origin.Tp != to.Tp {
-			msg := fmt.Sprintf("cannot modify enum type column's to type %s", to.String())
+			msg := fmt.Sprintf("cannot modify %s type column's to type %s", typeVar, to.String())
 			return errUnsupportedModifyColumn.GenWithStackByArgs(msg)
 		}
 		if len(to.Elems) < len(origin.Elems) {
-			msg := fmt.Sprintf("the number of enum column's elements is less than the original: %d", len(origin.Elems))
+			msg := fmt.Sprintf("the number of %s column's elements is less than the original: %d", typeVar, len(origin.Elems))
 			return errUnsupportedModifyColumn.GenWithStackByArgs(msg)
 		}
 		for index, originElem := range origin.Elems {
 			toElem := to.Elems[index]
 			if originElem != toElem {
-				msg := fmt.Sprintf("cannot modify enum column value %s to %s", originElem, toElem)
+				msg := fmt.Sprintf("cannot modify %s column value %s to %s", typeVar, originElem, toElem)
 				return errUnsupportedModifyColumn.GenWithStackByArgs(msg)
 			}
 		}
@@ -2999,6 +3005,10 @@ func (d *ddl) getModifiableColumnJob(ctx sessionctx.Context, ident ast.Ident, or
 		return nil, errors.Trace(err)
 	}
 
+	if err = checkColumnValueConstraint(newCol, newCol.Collate); err != nil {
+		return nil, errors.Trace(err)
+	}
+
 	if err = checkModifyTypes(&col.FieldType, &newCol.FieldType, isColumnWithIndex(col.Name.L, t.Meta().Indices)); err != nil {
 		if strings.Contains(err.Error(), "Unsupported modifying collation") {
 			colErrMsg := "Unsupported modifying collation of column '%s' from '%s' to '%s' when index is defined on it."
diff --git a/expression/integration_test.go b/expression/integration_test.go
index 7c552226a5202..d24c10d0fcff0 100755
--- a/expression/integration_test.go
+++ b/expression/integration_test.go
@@ -6951,7 +6951,25 @@ func (s *testIntegrationSuite) TestIssue19504(c *C) {
 		Check(testkit.Rows("1 1", "0 0", "0 0"))
 }
 
-func (s *testIntegrationSerialSuite) TestIssue17891(c *C) {
+func (s *testIntegrationSerialSuite) TestIssue19804(c *C) {
+	collate.SetNewCollationEnabledForTest(true)
+	defer collate.SetNewCollationEnabledForTest(false)
+
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec(`use test;`)
+	tk.MustExec(`drop table if exists t;`)
+	tk.MustExec(`create table t(a set('a', 'b', 'c'));`)
+	tk.MustGetErrMsg("alter table t change a a set('a', 'b', 'c', 'c');", "[types:1291]Column 'a' has duplicated value 'c' in SET")
+	tk.MustExec(`drop table if exists t;`)
+	tk.MustExec(`create table t(a enum('a', 'b', 'c'));`)
+	tk.MustGetErrMsg("alter table t change a a enum('a', 'b', 'c', 'c');", "[types:1291]Column 'a' has duplicated value 'c' in ENUM")
+	tk.MustExec(`drop table if exists t;`)
+	tk.MustExec(`create table t(a set('a', 'b', 'c'));`)
+	tk.MustExec(`alter table t change a a set('a', 'b', 'c', 'd');`)
+	tk.MustGetErrMsg(`alter table t change a a set('a', 'b', 'c', 'e', 'f');`, "[ddl:8200]Unsupported modify column: cannot modify set column value d to e")
+}
+
+func (s *testIntegrationSerialSuite) TestIssue18949(c *C) {
 	collate.SetNewCollationEnabledForTest(true)
 	defer collate.SetNewCollationEnabledForTest(false)