ddl: fix reorg handle not resumed after changing DDL owner (#56507)

ddl/backfilling.go

@@ -422,6 +422,7 @@ func splitTableRanges(t table.PhysicalTable, store kv.Storage, startKey, endKey
 		errMsg := fmt.Sprintf("cannot find region in range [%s, %s]", startKey.String(), endKey.String())
 		return nil, errors.Trace(dbterror.ErrInvalidSplitRegionRanges.GenWithStackByArgs(errMsg))
 	}
+	failpoint.InjectCall("afterLoadTableRanges", len(ranges))
 	return ranges, nil
 }
 
@@ -534,6 +535,7 @@ func handleOneResult(result *backfillResult, scheduler backfillScheduler, consum
 				logutil.BgLogger().Warn("[ddl] update reorg meta failed",
 					zap.Int64("job ID", reorgInfo.ID), zap.Error(err))
 			}
+			failpoint.InjectCall("afterUpdateReorgMeta")
 		}
 		// We try to adjust the worker size regularly to reduce
 		// the overhead of loading the DDL related global variables.
@@ -681,7 +683,7 @@ func SetBackfillTaskChanSizeForTest(n int) {
 //
 // The above operations are completed in a transaction.
 // Finally, update the concurrent processing of the total number of rows, and store the completed handle value.
-func (dc *ddlCtx) writePhysicalTableRecord(sessPool *sess.Pool, t table.PhysicalTable, bfWorkerType backfillerType, reorgInfo *reorgInfo) error {
+func (dc *ddlCtx) writePhysicalTableRecord(sessPool *sess.Pool, t table.PhysicalTable, bfWorkerType backfillerType, reorgInfo *reorgInfo) (err error) {
 	job := reorgInfo.Job
 	totalAddedCount := job.GetRowCount()
 

ddl/backfilling_scheduler.go

@@ -506,6 +506,7 @@ func newTaskIDAllocator() *taskIDAllocator {
 }
 
 func (a *taskIDAllocator) alloc() int {
+	ret := a.id
 	a.id++
-	return a.id
+	return ret
 }

ddl/column_modify_test.go

@@ -24,6 +24,7 @@ import (
 	"time"
 
 	"github.com/pingcap/errors"
+	"github.com/pingcap/failpoint"
 	testddlutil "github.com/pingcap/tidb/ddl/testutil"
 	"github.com/pingcap/tidb/ddl/util/callback"
 	"github.com/pingcap/tidb/domain"
@@ -1029,3 +1030,44 @@ func TestColumnTypeChangeGenUniqueChangingName(t *testing.T) {
 
 	tk.MustExec("drop table if exists t")
 }
+
+func TestModifyColumnReorgCheckpoint(t *testing.T) {
+	store, dom := testkit.CreateMockStoreAndDomainWithSchemaLease(t, columnModifyLease)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk2 := testkit.NewTestKit(t, store)
+	tk2.MustExec("use test")
+	tk.MustExec("set global tidb_ddl_reorg_worker_cnt = 1;")
+	tk.MustExec("create table t (a int primary key, b bigint);")
+	rowCnt := 10
+	for i := 0; i < rowCnt; i++ {
+		tk.MustExec(fmt.Sprintf("insert into t values (%d, %d)", i*10000, i*10000))
+	}
+	splitTableSQL := fmt.Sprintf("split table t between (0) and (%d*10000) regions %d;", rowCnt, rowCnt)
+	tk.MustQuery(splitTableSQL).Check(testkit.Rows(fmt.Sprintf("%d 1", rowCnt-1)))
+
+	retireOwner := false
+	err := failpoint.EnableCall("github.com/pingcap/tidb/pkg/ddl/afterUpdateReorgMeta", func() {
+		if !retireOwner {
+			retireOwner = true
+			dom.DDL().OwnerManager().ResignOwner(context.Background())
+		}
+	})
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, failpoint.Disable("github.com/pingcap/tidb/pkg/ddl/afterUpdateReorgMeta"))
+	}()
+
+	rangeCnts := []int{}
+	err = failpoint.EnableCall("github.com/pingcap/tidb/pkg/ddl/afterLoadTableRanges", func(rangeCnt int) {
+		rangeCnts = append(rangeCnts, rangeCnt)
+	})
+	require.NoError(t, err)
+	defer func() {
+		require.NoError(t, failpoint.Disable("github.com/pingcap/tidb/pkg/ddl/afterLoadTableRanges"))
+	}()
+
+	tk.MustExec("alter table t modify column b int;")
+	require.Len(t, rangeCnts, 2)                // It should have two rounds for loading table ranges.
+	require.Less(t, rangeCnts[1], rangeCnts[0]) // Verify if the checkpoint is progressing.
+}

ddl/ingest/checkpoint.go

@@ -55,7 +55,7 @@ type CheckpointManager struct {
 	// Live in memory.
 	mu          sync.Mutex
 	checkpoints map[int]*taskCheckpoint // task ID -> checkpoint
-	// we require each task ID to be continuous and start from 1.
+	// we require each task ID to be continuous and start from 0.
 	minTaskIDFinished int
 	dirty             bool
 	// Local meta.
@@ -166,7 +166,7 @@ func (s *CheckpointManager) Status() (keyCnt int, minKeyImported kv.Key) {
 }
 
 // Register registers a new task. taskID MUST be continuous ascending and start
-// from 1.
+// from 0.
 //
 // TODO(lance6716): remove this constraint, use endKey as taskID and use
 // ordered map type for checkpoints.
@@ -219,14 +219,14 @@ func (s *CheckpointManager) UpdateWrittenKeys(taskID int, delta int) error {
 // afterFlush should be called after all engine is flushed.
 func (s *CheckpointManager) afterFlush() {
 	for {
-		cp := s.checkpoints[s.minTaskIDFinished+1]
+		cp := s.checkpoints[s.minTaskIDFinished]
 		if cp == nil || !cp.lastBatchRead || cp.writtenKeys < cp.totalKeys {
 			break
 		}
+		delete(s.checkpoints, s.minTaskIDFinished)
 		s.minTaskIDFinished++
 		s.minFlushedKey = cp.endKey
 		s.flushedKeyCnt += cp.totalKeys
-		delete(s.checkpoints, s.minTaskIDFinished)
 		s.dirty = true
 	}
 }

ddl/ingest/checkpoint_test.go

@@ -52,39 +52,39 @@ func TestCheckpointManager(t *testing.T) {
 	require.NoError(t, err)
 	defer mgr.Close()
 
-	mgr.Register(1, []byte{'1', '9'})
-	mgr.Register(2, []byte{'2', '9'})
-	mgr.UpdateTotalKeys(1, 100, false)
+	mgr.Register(0, []byte{'1', '9'})
+	mgr.Register(1, []byte{'2', '9'})
+	mgr.UpdateTotalKeys(0, 100, false)
 	require.False(t, mgr.IsKeyProcessed([]byte{'1', '9'}))
-	require.NoError(t, mgr.UpdateWrittenKeys(1, 100))
+	require.NoError(t, mgr.UpdateWrittenKeys(0, 100))
 	require.False(t, mgr.IsKeyProcessed([]byte{'1', '9'}))
-	mgr.UpdateTotalKeys(1, 100, true)
-	require.NoError(t, mgr.UpdateWrittenKeys(1, 100))
+	mgr.UpdateTotalKeys(0, 100, true)
+	require.NoError(t, mgr.UpdateWrittenKeys(0, 100))
 	// The data is not imported to the storage yet.
 	require.False(t, mgr.IsKeyProcessed([]byte{'1', '9'}))
 	flushCtrl.imported = true // Mock the data is imported to the storage.
-	require.NoError(t, mgr.UpdateWrittenKeys(2, 0))
+	require.NoError(t, mgr.UpdateWrittenKeys(1, 0))
 	require.True(t, mgr.IsKeyProcessed([]byte{'1', '9'}))
 
 	// Only when the last batch is completed, the job can be completed.
-	mgr.UpdateTotalKeys(2, 50, false)
-	mgr.UpdateTotalKeys(2, 50, true)
-	require.NoError(t, mgr.UpdateWrittenKeys(2, 50))
+	mgr.UpdateTotalKeys(1, 50, false)
+	mgr.UpdateTotalKeys(1, 50, true)
+	require.NoError(t, mgr.UpdateWrittenKeys(1, 50))
 	require.True(t, mgr.IsKeyProcessed([]byte{'1', '9'}))
 	require.False(t, mgr.IsKeyProcessed([]byte{'2', '9'}))
-	require.NoError(t, mgr.UpdateWrittenKeys(2, 50))
+	require.NoError(t, mgr.UpdateWrittenKeys(1, 50))
 	require.True(t, mgr.IsKeyProcessed([]byte{'1', '9'}))
 	require.True(t, mgr.IsKeyProcessed([]byte{'2', '9'}))
 
 	// Only when the subsequent job is completed, the previous job can be completed.
-	mgr.Register(3, []byte{'3', '9'})
-	mgr.Register(4, []byte{'4', '9'})
-	mgr.Register(5, []byte{'5', '9'})
+	mgr.Register(2, []byte{'3', '9'})
+	mgr.Register(3, []byte{'4', '9'})
+	mgr.Register(4, []byte{'5', '9'})
+	mgr.UpdateTotalKeys(2, 100, true)
 	mgr.UpdateTotalKeys(3, 100, true)
 	mgr.UpdateTotalKeys(4, 100, true)
-	mgr.UpdateTotalKeys(5, 100, true)
-	require.NoError(t, mgr.UpdateWrittenKeys(5, 100))
 	require.NoError(t, mgr.UpdateWrittenKeys(4, 100))
+	require.NoError(t, mgr.UpdateWrittenKeys(3, 100))
 	require.False(t, mgr.IsKeyProcessed([]byte{'3', '9'}))
 	require.False(t, mgr.IsKeyProcessed([]byte{'4', '9'}))
 }
@@ -107,9 +107,9 @@ func TestCheckpointManagerUpdateReorg(t *testing.T) {
 	require.NoError(t, err)
 	defer mgr.Close()
 
-	mgr.Register(1, []byte{'1', '9'})
-	mgr.UpdateTotalKeys(1, 100, true)
-	require.NoError(t, mgr.UpdateWrittenKeys(1, 100))
+	mgr.Register(0, []byte{'1', '9'})
+	mgr.UpdateTotalKeys(0, 100, true)
+	require.NoError(t, mgr.UpdateWrittenKeys(0, 100))
 	mgr.Flush() // Wait the global checkpoint to be updated to the reorg table.
 	r, err := tk.Exec("select reorg_meta from mysql.tidb_ddl_reorg where job_id = 1 and ele_id = 1;")
 	require.NoError(t, err)