ddl: check foreign key constraint when drop,modify,change column (pin…

…gcap#14043)

ddl/column.go

@@ -534,6 +534,17 @@ func isColumnWithIndex(colName string, indices []*model.IndexInfo) bool {
 	return false
 }
 
+func getColumnForeignKeyInfo(colName string, fkInfos []*model.FKInfo) *model.FKInfo {
+	for _, fkInfo := range fkInfos {
+		for _, col := range fkInfo.Cols {
+			if col.L == colName {
+				return fkInfo
+			}
+		}
+	}
+	return nil
+}
+
 func allocateColumnID(tblInfo *model.TableInfo) int64 {
 	tblInfo.MaxColumnID++
 	return tblInfo.MaxColumnID

ddl/db_test.go

@@ -2067,7 +2067,21 @@ func (s *testDBSuite2) TestTableForeignKey(c *C) {
 	s.tk.MustExec("create table t3 (a int, b int);")
 	failSQL = "alter table t1 add foreign key (c) REFERENCES t3(a);"
 	assertErrorCode(c, s.tk, failSQL, tmysql.ErrKeyColumnDoesNotExits)
-	s.tk.MustExec("drop table if exists t1,t2,t3;")
+
+	// Test drop column with foreign key.
+	s.tk.MustExec("create table t4 (c int,d int,foreign key (d) references t1 (b));")
+	failSQL = "alter table t4 drop column d"
+	s.tk.MustGetErrCode(failSQL, mysql.ErrFkColumnCannotDrop)
+	// Test change column with foreign key.
+	failSQL = "alter table t4 change column d e bigint;"
+	s.tk.MustGetErrCode(failSQL, mysql.ErrFKIncompatibleColumns)
+	// Test modify column with foreign key.
+	failSQL = "alter table t4 modify column d bigint;"
+	s.tk.MustGetErrCode(failSQL, mysql.ErrFKIncompatibleColumns)
+	s.tk.MustQuery("select count(*) from information_schema.KEY_COLUMN_USAGE;")
+	s.tk.MustExec("alter table t4 drop foreign key d")
+	s.tk.MustExec("alter table t4 modify column d bigint;")
+	s.tk.MustExec("drop table if exists t1,t2,t3,t4;")
 }
 
 func (s *testDBSuite3) TestTruncateTable(c *C) {

ddl/ddl.go

@@ -113,6 +113,8 @@ var (
 	errTooManyFields            = terror.ClassDDL.New(codeTooManyFields, "Too many columns")
 	errInvalidSplitRegionRanges = terror.ClassDDL.New(codeInvalidRanges, "Failed to split region ranges")
 	errReorgPanic               = terror.ClassDDL.New(codeReorgWorkerPanic, "reorg worker panic.")
+	errFkColumnCannotDrop       = terror.ClassDDL.New(mysql.ErrFkColumnCannotDrop, mysql.MySQLErrName[mysql.ErrFkColumnCannotDrop])
+	errReferencedForeignKey     = terror.ClassDDL.New(mysql.ErrFKIncompatibleColumns, mysql.MySQLErrName[mysql.ErrFKIncompatibleColumns])
 
 	errOnlyOnRangeListPartition = terror.ClassDDL.New(codeOnlyOnRangeListPartition, mysql.MySQLErrName[mysql.ErrOnlyOnRangeListPartition])
 	// errWrongKeyColumn is for table column cannot be indexed.
@@ -826,6 +828,8 @@ func init() {
 		codeSystemVersioningWrongPartitions:        mysql.ErrSystemVersioningWrongPartitions,
 		codeWrongPartitionTypeExpectedSystemTime:   mysql.ErrWrongPartitionTypeExpectedSystemTime,
 		codeWrongTypeColumnValue:                   mysql.ErrWrongTypeColumnValue,
+		mysql.ErrFkColumnCannotDrop:                mysql.ErrFkColumnCannotDrop,
+		mysql.ErrFKIncompatibleColumns:             mysql.ErrFKIncompatibleColumns,
 	}
 	terror.ErrClassToMySQLCodes[terror.ClassDDL] = ddlMySQLErrCodes
 }

ddl/ddl_api.go

@@ -2571,6 +2571,10 @@ func (d *ddl) getModifiableColumnJob(ctx sessionctx.Context, ident ast.Ident, or
 			return nil, infoschema.ErrColumnExists.GenWithStackByArgs(newColName)
 		}
 	}
+	// Check the column with foreign key.
+	if fkInfo := getColumnForeignKeyInfo(originalColName.L, t.Meta().ForeignKeys); fkInfo != nil {
+		return nil, errReferencedForeignKey.GenWithStackByArgs(originalColName, fkInfo.Name)
+	}
 
 	// Constraints in the new column means adding new constraints. Errors should thrown,
 	// which will be done by `processColumnOptions` later.
@@ -3379,6 +3383,10 @@ func isDroppableColumn(tblInfo *model.TableInfo, colName model.CIStr) error {
 	if isColumnWithIndex(colName.L, tblInfo.Indices) {
 		return errCantDropColWithIndex.GenWithStack("can't drop column %s with index covered now", colName)
 	}
+	// Check the column with foreign key.
+	if fkInfo := getColumnForeignKeyInfo(colName.L, tblInfo.ForeignKeys); fkInfo != nil {
+		return errFkColumnCannotDrop.GenWithStackByArgs(colName, fkInfo.Name)
+	}
 	return nil
 }
 

go.mod

@@ -75,3 +75,5 @@ require (
 )
 
 go 1.13
+
+replace github.com/pingcap/parser => github.com/crazycs520/parser v0.0.0-20191218032222-cb5d742ae9e0

go.sum

@@ -24,6 +24,8 @@ github.com/coreos/go-systemd v0.0.0-20181031085051-9002847aa142/go.mod h1:F5haX7
 github.com/coreos/pkg v0.0.0-20160727233714-3ac0863d7acf/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
 github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f h1:lBNOc5arjvs8E5mO2tbpBpLoyyu8B6e44T7hJy6potg=
 github.com/coreos/pkg v0.0.0-20180928190104-399ea9e2e55f/go.mod h1:E3G3o1h8I7cfcXa63jLwjI0eiQQMgzzUDFVpN/nH/eA=
+github.com/crazycs520/parser v0.0.0-20191218032222-cb5d742ae9e0 h1:3Z4NvkQhzgJsMhY1x7EVwh167Rk49Fwc1/8RoDQ8Yhc=
+github.com/crazycs520/parser v0.0.0-20191218032222-cb5d742ae9e0/go.mod h1:xLjI+gnWYexq011WPMEvCNS8rFM9qe1vdojIEzSKPuc=
 github.com/cznic/mathutil v0.0.0-20181122101859-297441e03548 h1:iwZdTE0PVqJCos1vaoKsclOGD3ADKpshg3SRtYBbwso=
 github.com/cznic/mathutil v0.0.0-20181122101859-297441e03548/go.mod h1:e6NPNENfs9mPDVNRekM7lKScauxd5kXTr1Mfyig6TDM=
 github.com/cznic/sortutil v0.0.0-20150617083342-4c7342852e65 h1:hxuZop6tSoOi0sxFzoGGYdRqNrPubyaIf9KoBG9tPiE=