This is an automated cherry-pick of #44129

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>

ddl/partition.go

@@ -283,6 +283,25 @@ func alterTablePartitionBundles(t *meta.Meta, tblInfo *model.TableInfo, addingDe
 	return bundles, nil
 }
 
+// When drop/truncate a partition, we should still keep the dropped partition's placement settings to avoid unnecessary region schedules.
+// When a partition is not configured with a placement policy directly, its rule is in the table's placement group which will be deleted after
+// partition truncated/dropped. So it is necessary to create a standalone placement group with partition id after it.
+func droppedPartitionBundles(t *meta.Meta, tblInfo *model.TableInfo, dropPartitions []model.PartitionDefinition) ([]*placement.Bundle, error) {
+	partitions := make([]model.PartitionDefinition, 0, len(dropPartitions))
+	for _, def := range dropPartitions {
+		def = def.Clone()
+		if def.PlacementPolicyRef == nil {
+			def.PlacementPolicyRef = tblInfo.PlacementPolicyRef
+		}
+
+		if def.PlacementPolicyRef != nil {
+			partitions = append(partitions, def)
+		}
+	}
+
+	return placement.NewPartitionListBundles(t, partitions)
+}
+
 // updatePartitionInfo merge `addingDefinitions` into `Definitions` in the tableInfo.
 func updatePartitionInfo(tblInfo *model.TableInfo) {
 	parInfo := &model.PartitionInfo{}
@@ -1820,6 +1839,32 @@ func (w *worker) onDropTablePartition(d *ddlCtx, t *meta.Meta, job *model.Job) (
 			return ver, err
 		}
 
+		var bundles []*placement.Bundle
+		// create placement groups for each dropped partition to keep the data's placement before GC
+		// These placements groups will be deleted after GC
+		bundles, err = droppedPartitionBundles(t, tblInfo, tblInfo.Partition.DroppingDefinitions)
+		if err != nil {
+			job.State = model.JobStateCancelled
+			return ver, err
+		}
+
+		var tableBundle *placement.Bundle
+		// Recompute table bundle to remove dropped partitions rules from its group
+		tableBundle, err = placement.NewTableBundle(t, tblInfo)
+		if err != nil {
+			job.State = model.JobStateCancelled
+			return ver, errors.Trace(err)
+		}
+
+		if tableBundle != nil {
+			bundles = append(bundles, tableBundle)
+		}
+
+		if err = infosync.PutRuleBundlesWithDefaultRetry(context.TODO(), bundles); err != nil {
+			job.State = model.JobStateCancelled
+			return ver, err
+		}
+
 		job.SchemaState = model.StateDeleteOnly
 		ver, err = updateVersionAndTableInfo(d, t, job, tblInfo, originalState != job.SchemaState)
 	case model.StateDeleteOnly:
@@ -1915,11 +1960,13 @@ func onTruncateTablePartition(d *ddlCtx, t *meta.Meta, job *model.Job) (int64, e
 		return ver, errors.Trace(dbterror.ErrPartitionMgmtOnNonpartitioned)
 	}
 
+	oldPartitions := make([]model.PartitionDefinition, 0, len(oldIDs))
 	newPartitions := make([]model.PartitionDefinition, 0, len(oldIDs))
 	for _, oldID := range oldIDs {
 		for i := 0; i < len(pi.Definitions); i++ {
 			def := &pi.Definitions[i]
 			if def.ID == oldID {
+				oldPartitions = append(oldPartitions, def.Clone())
 				pid, err1 := t.GenGlobalID()
 				if err1 != nil {
 					return ver, errors.Trace(err1)
@@ -1967,6 +2014,28 @@ func onTruncateTablePartition(d *ddlCtx, t *meta.Meta, job *model.Job) (int64, e
 		return ver, errors.Trace(err)
 	}
 
+<<<<<<< HEAD
+=======
+	tableBundle, err := placement.NewTableBundle(t, tblInfo)
+	if err != nil {
+		job.State = model.JobStateCancelled
+		return ver, errors.Trace(err)
+	}
+
+	if tableBundle != nil {
+		bundles = append(bundles, tableBundle)
+	}
+
+	// create placement groups for each dropped partition to keep the data's placement before GC
+	// These placements groups will be deleted after GC
+	keepDroppedBundles, err := droppedPartitionBundles(t, tblInfo, oldPartitions)
+	if err != nil {
+		job.State = model.JobStateCancelled
+		return ver, errors.Trace(err)
+	}
+	bundles = append(bundles, keepDroppedBundles...)
+
+>>>>>>> f7ccac1c230 (ddl: fix the placement behavior when drop/truncate partitions (#44129))
 	err = infosync.PutRuleBundlesWithDefaultRetry(context.TODO(), bundles)
 	if err != nil {
 		job.State = model.JobStateCancelled