ddl: fix cancel drop column ddl error (pingcap#8545)

ddl/db_test.go

@@ -884,6 +884,94 @@ LOOP:
 	s.tk.MustExec("drop table test_drop_index")
 }
 
+// TestCancelDropColumn tests cancel ddl job which type is drop column.
+func (s *testDBSuite) TestCancelDropColumn(c *C) {
+	s.tk = testkit.NewTestKit(c, s.store)
+	s.tk.MustExec("use " + s.schemaName)
+	s.mustExec(c, "drop table if exists test_drop_column")
+	s.mustExec(c, "create table test_drop_column(c1 int, c2 int)")
+	defer s.mustExec(c, "drop table test_drop_column;")
+	testCases := []struct {
+		needAddColumn  bool
+		jobState       model.JobState
+		JobSchemaState model.SchemaState
+		cancelSucc     bool
+	}{
+		{true, model.JobStateNone, model.StateNone, true},
+		{false, model.JobStateRunning, model.StateWriteOnly, false},
+		{true, model.JobStateRunning, model.StateDeleteOnly, false},
+		{true, model.JobStateRunning, model.StateDeleteReorganization, false},
+	}
+	var checkErr error
+	oldReorgWaitTimeout := ddl.ReorgWaitTimeout
+	ddl.ReorgWaitTimeout = 50 * time.Millisecond
+	defer func() { ddl.ReorgWaitTimeout = oldReorgWaitTimeout }()
+	hook := &ddl.TestDDLCallback{}
+	var jobID int64
+	testCase := &testCases[0]
+	hook.OnJobRunBeforeExported = func(job *model.Job) {
+		if job.Type == model.ActionDropColumn && job.State == testCase.jobState && job.SchemaState == testCase.JobSchemaState {
+			jobIDs := []int64{job.ID}
+			jobID = job.ID
+			hookCtx := mock.NewContext()
+			hookCtx.Store = s.store
+			err := hookCtx.NewTxn(context.TODO())
+			if err != nil {
+				checkErr = errors.Trace(err)
+				return
+			}
+			txn, err := hookCtx.Txn(true)
+			if err != nil {
+				checkErr = errors.Trace(err)
+				return
+			}
+			errs, err := admin.CancelJobs(txn, jobIDs)
+			if err != nil {
+				checkErr = errors.Trace(err)
+				return
+			}
+			if errs[0] != nil {
+				checkErr = errors.Trace(errs[0])
+				return
+			}
+			checkErr = txn.Commit(context.Background())
+		}
+	}
+
+	originalHook := s.dom.DDL().GetHook()
+	s.dom.DDL().(ddl.DDLForTest).SetHook(hook)
+	var err1 error
+	for i := range testCases {
+		testCase = &testCases[i]
+		if testCase.needAddColumn {
+			s.mustExec(c, "alter table test_drop_column add column c3 int")
+		}
+		_, err1 = s.tk.Exec("alter table test_drop_column drop column c3")
+		var col1 *table.Column
+		t := s.testGetTable(c, "test_drop_column")
+		for _, col := range t.Cols() {
+			if strings.EqualFold(col.Name.L, "c3") {
+				col1 = col
+				break
+			}
+		}
+		if testCase.cancelSucc {
+			c.Assert(checkErr, IsNil)
+			c.Assert(col1, NotNil)
+			c.Assert(col1.Name.L, Equals, "c3")
+			c.Assert(err1.Error(), Equals, "[ddl:12]cancelled DDL job")
+		} else {
+			c.Assert(col1, IsNil)
+			c.Assert(err1, IsNil)
+			c.Assert(checkErr, NotNil)
+			c.Assert(checkErr.Error(), Equals, admin.ErrCannotCancelDDLJob.GenWithStackByArgs(jobID).Error())
+		}
+	}
+	s.dom.DDL().(ddl.DDLForTest).SetHook(originalHook)
+	s.mustExec(c, "alter table test_drop_column add column c3 int")
+	s.mustExec(c, "alter table test_drop_column drop column c3")
+}
+
 func checkDelRangeDone(c *C, ctx sessionctx.Context, idx table.Index) {
 	startTime := time.Now()
 	f := func() map[int64]struct{} {

ddl/ddl_worker_test.go

@@ -374,6 +374,10 @@ func buildCancelJobTests(firstID int64) []testCancelJob {
 		{act: model.ActionCreateTable, jobIDs: []int64{firstID + 10}, cancelRetErrs: noErrs, cancelState: model.StateNone, ddlRetErr: err},
 		// Test create database, watch out, database id will alloc a globalID.
 		{act: model.ActionCreateSchema, jobIDs: []int64{firstID + 12}, cancelRetErrs: noErrs, cancelState: model.StateNone, ddlRetErr: err},
+
+		{act: model.ActionDropColumn, jobIDs: []int64{firstID + 13}, cancelRetErrs: []error{admin.ErrCancelFinishedDDLJob.GenWithStackByArgs(firstID + 13)}, cancelState: model.StateDeleteOnly, ddlRetErr: err},
+		{act: model.ActionDropColumn, jobIDs: []int64{firstID + 14}, cancelRetErrs: []error{admin.ErrCancelFinishedDDLJob.GenWithStackByArgs(firstID + 14)}, cancelState: model.StateWriteOnly, ddlRetErr: err},
+		{act: model.ActionDropColumn, jobIDs: []int64{firstID + 15}, cancelRetErrs: []error{admin.ErrCancelFinishedDDLJob.GenWithStackByArgs(firstID + 15)}, cancelState: model.StateWriteReorganization, ddlRetErr: err},
 	}
 
 	return tests
@@ -403,6 +407,18 @@ func (s *testDDLSuite) checkAddColumn(c *C, d *ddl, schemaID int64, tableID int6
 	c.Assert(found, Equals, success)
 }
 
+func (s *testDDLSuite) checkCancelDropColumn(c *C, d *ddl, schemaID int64, tableID int64, colName string, success bool) {
+	changedTable := testGetTable(c, d, schemaID, tableID)
+	notFound := true
+	for _, colInfo := range changedTable.Meta().Columns {
+		if colInfo.Name.O == colName {
+			notFound = false
+			break
+		}
+	}
+	c.Assert(notFound, Equals, success)
+}
+
 func (s *testDDLSuite) TestCancelJob(c *C) {
 	store := testCreateStore(c, "test_cancel_job")
 	defer store.Close()
@@ -541,6 +557,23 @@ func (s *testDDLSuite) TestCancelJob(c *C) {
 	c.Check(checkErr, IsNil)
 	testCheckSchemaState(c, d, dbInfo1, model.StateNone)
 
+	// for drop column.
+	test = &tests[10]
+	dropColName := "c2"
+	dropColumnArgs := []interface{}{model.NewCIStr(dropColName)}
+	doDDLJobErrWithSchemaState(ctx, d, c, dbInfo.ID, tblInfo.ID, model.ActionDropColumn, dropColumnArgs, &cancelState)
+	c.Check(errors.ErrorStack(checkErr), Equals, "")
+	s.checkCancelDropColumn(c, d, dbInfo.ID, tblInfo.ID, dropColName, false)
+
+	test = &tests[11]
+	doDDLJobErrWithSchemaState(ctx, d, c, dbInfo.ID, tblInfo.ID, model.ActionDropColumn, dropColumnArgs, &cancelState)
+	c.Check(errors.ErrorStack(checkErr), Equals, "")
+	s.checkCancelDropColumn(c, d, dbInfo.ID, tblInfo.ID, dropColName, false)
+
+	test = &tests[12]
+	doDDLJobErrWithSchemaState(ctx, d, c, dbInfo.ID, tblInfo.ID, model.ActionDropColumn, dropColumnArgs, &cancelState)
+	c.Check(errors.ErrorStack(checkErr), Equals, "")
+	s.checkCancelDropColumn(c, d, dbInfo.ID, tblInfo.ID, dropColName, false)
 }
 
 func (s *testDDLSuite) TestIgnorableSpec(c *C) {

ddl/rollingback.go

@@ -118,6 +118,38 @@ func rollingbackAddColumn(t *meta.Meta, job *model.Job) (ver int64, err error) {
 	return ver, errCancelledDDLJob
 }
 
+func rollingbackDropColumn(t *meta.Meta, job *model.Job) (ver int64, err error) {
+	tblInfo, err := getTableInfo(t, job, job.SchemaID)
+	if err != nil {
+		return ver, errors.Trace(err)
+	}
+
+	var colName model.CIStr
+	err = job.DecodeArgs(&colName)
+	if err != nil {
+		job.State = model.JobStateCancelled
+		return ver, errors.Trace(err)
+	}
+
+	colInfo := model.FindColumnInfo(tblInfo.Columns, colName.L)
+	if colInfo == nil {
+		job.State = model.JobStateCancelled
+		return ver, ErrCantDropFieldOrKey.GenWithStack("column %s doesn't exist", colName)
+	}
+
+	// StatePublic means when the job is not running yet.
+	if colInfo.State == model.StatePublic {
+		job.State = model.JobStateCancelled
+	} else {
+		// In the state of drop column `write only -> delete only -> reorganization`,
+		// We can not rollback now, so just continue to drop column.
+		job.State = model.JobStateRunning
+		return ver, errors.Trace(nil)
+	}
+	job.FinishTableJob(model.JobStateRollbackDone, model.StatePublic, ver, tblInfo)
+	return ver, errors.Trace(errCancelledDDLJob)
+}
+
 func rollingbackDropIndex(t *meta.Meta, job *model.Job) (ver int64, err error) {
 	schemaID := job.SchemaID
 	tblInfo, err := getTableInfo(t, job, schemaID)
@@ -182,6 +214,8 @@ func convertJob2RollbackJob(w *worker, d *ddlCtx, t *meta.Meta, job *model.Job)
 		ver, err = rollingbackAddColumn(t, job)
 	case model.ActionAddIndex:
 		ver, err = rollingbackAddindex(w, d, t, job)
+	case model.ActionDropColumn:
+		ver, err = rollingbackDropColumn(t, job)
 	case model.ActionDropIndex:
 		ver, err = rollingbackDropIndex(t, job)
 	case model.ActionDropTable, model.ActionDropSchema:

util/admin/admin.go

@@ -91,6 +91,10 @@ func isJobRollbackable(job *model.Job, id int64) error {
 			job.SchemaState == model.StateDeleteReorganization {
 			return ErrCannotCancelDDLJob.GenWithStackByArgs(id)
 		}
+	case model.ActionDropColumn:
+		if job.SchemaState != model.StateNone {
+			return ErrCannotCancelDDLJob.GenWithStackByArgs(id)
+		}
 	case model.ActionDropSchema, model.ActionDropTable:
 		// To simplify the rollback logic, cannot be canceled in the following states.
 		if job.SchemaState == model.StateWriteOnly ||