statistics: enhance DDL subscriber to handle schema drop events and update stats meta

Signed-off-by: Rustin170506 <[email protected]>

Author: 0xPoe

pkg/statistics/handle/ddl/subscriber.go

@@ -232,7 +232,20 @@ func (h subscriber) handle(
 	case model.ActionFlashbackCluster:
 		return errors.Trace(storage.UpdateStatsVersion(ctx, sctx))
 	case model.ActionAddIndex:
-		// No need to update the stats meta for the adding index event.
+	// 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",