statistics: rename subscriber and handle drop schema event (#58009)

ref pingcap/tidb#57871

pkg/statistics/handle/ddl/subscriber.go

@@ -31,21 +31,19 @@ import (
 	"go.uber.org/zap"
 )
 
-type handler struct {
+type subscriber struct {
 	statsCache types.StatsCache
 }
 
-// NewHandlerAndRegister creates a new handler and registers it to the DDL
-// notifier.
-func NewHandlerAndRegister(
+// NewSubscriber creates a new subscriber.
+func NewSubscriber(
 	statsCache types.StatsCache,
-	registry *notifier.DDLNotifier,
-) {
-	h := handler{statsCache: statsCache}
-	registry.RegisterHandler(notifier.StatsMetaHandlerID, h.handle)
+) *subscriber {
+	h := subscriber{statsCache: statsCache}
+	return &h
 }
 
-func (h handler) handle(
+func (h subscriber) handle(
 	ctx context.Context,
 	sctx sessionctx.Context,
 	change *notifier.SchemaChangeEvent,
@@ -235,6 +233,19 @@ func (h handler) handle(
 		return errors.Trace(storage.UpdateStatsVersion(ctx, sctx))
 	case model.ActionAddIndex:
 		// No need to update the stats meta for the adding index event.
+	case model.ActionDropSchema:
+		miniDBInfo := change.GetDropSchemaInfo()
+		intest.Assert(miniDBInfo != nil)
+		for _, table := range miniDBInfo.Tables {
+			// Try best effort to update the stats meta version for gc.
+			if err := h.delayedDeleteStats4PhysicalID(ctx, sctx, table.ID); err != nil {
+				logutil.StatsLogger().Error(
+					"Failed to update stats meta version for gc",
+					zap.Int64("tableID", table.ID),
+					zap.Error(err),
+				)
+			}
+		}
 	default:
 		intest.Assert(false)
 		logutil.StatsLogger().Error("Unhandled schema change event",
@@ -243,7 +254,7 @@ func (h handler) handle(
 	return nil
 }
 
-func (h handler) insertStats4PhysicalID(
+func (h subscriber) insertStats4PhysicalID(
 	ctx context.Context,
 	sctx sessionctx.Context,
 	info *model.TableInfo,
@@ -256,7 +267,7 @@ func (h handler) insertStats4PhysicalID(
 	return errors.Trace(h.recordHistoricalStatsMeta(ctx, sctx, id, startTS))
 }
 
-func (h handler) recordHistoricalStatsMeta(
+func (h subscriber) recordHistoricalStatsMeta(
 	ctx context.Context,
 	sctx sessionctx.Context,
 	id int64,
@@ -287,7 +298,7 @@ func (h handler) recordHistoricalStatsMeta(
 	)
 }
 
-func (h handler) delayedDeleteStats4PhysicalID(
+func (h subscriber) delayedDeleteStats4PhysicalID(
 	ctx context.Context,
 	sctx sessionctx.Context,
 	id int64,
@@ -299,7 +310,7 @@ func (h handler) delayedDeleteStats4PhysicalID(
 	return errors.Trace(h.recordHistoricalStatsMeta(ctx, sctx, id, startTS))
 }
 
-func (h handler) insertStats4Col(
+func (h subscriber) insertStats4Col(
 	ctx context.Context,
 	sctx sessionctx.Context,
 	physicalID int64,