statistics: avoid oom when to gc large stats_history (#48430) (#48489)

close #48431

executor/historical_stats_test.go

@@ -237,8 +237,10 @@ func TestAssertHistoricalStatsAfterAlterTable(t *testing.T) {
 }
 
 func TestGCOutdatedHistoryStats(t *testing.T) {
-	failpoint.Enable("github.com/pingcap/tidb/domain/sendHistoricalStats", "return(true)")
-	defer failpoint.Disable("github.com/pingcap/tidb/domain/sendHistoricalStats")
+	require.NoError(t, failpoint.Enable("github.com/pingcap/tidb/domain/sendHistoricalStats", "return(true)"))
+	defer func() {
+		require.NoError(t, failpoint.Disable("github.com/pingcap/tidb/domain/sendHistoricalStats"))
+	}()
 	store, dom := testkit.CreateMockStoreAndDomain(t)
 	tk := testkit.NewTestKit(t, store)
 	tk.MustExec("set global tidb_enable_historical_stats = 1")

statistics/handle/gc.go

@@ -151,6 +151,14 @@ func (h *Handle) gcTableStats(is infoschema.InfoSchema, physicalID int64) error
 	return nil
 }
 
+func forCount(total int64, batch int64) int64 {
+	result := total / batch
+	if total%batch > 0 {
+		result++
+	}
+	return result
+}
+
 // ClearOutdatedHistoryStats clear outdated historical stats
 func (h *Handle) ClearOutdatedHistoryStats() error {
 	ctx := kv.WithInternalSourceType(context.Background(), kv.InternalTxnStats)
@@ -172,15 +180,19 @@ func (h *Handle) ClearOutdatedHistoryStats() error {
 	}
 	count := rows[0].GetInt64(0)
 	if count > 0 {
-		sql = "delete from mysql.stats_meta_history use index (idx_create_time) where create_time <= NOW() - INTERVAL %? SECOND"
-		_, err = exec.ExecuteInternal(ctx, sql, variable.HistoricalStatsDuration.Load().Seconds())
-		if err != nil {
+		for n := int64(0); n < forCount(count, int64(1000)); n++ {
+			sql = "delete from mysql.stats_meta_history use index (idx_create_time) where create_time <= NOW() - INTERVAL %? SECOND limit 1000 "
+			_, err = exec.ExecuteInternal(ctx, sql, variable.HistoricalStatsDuration.Load().Seconds())
+			if err != nil {
+				return err
+			}
+		}
+		for n := int64(0); n < forCount(count, int64(50)); n++ {
+			sql = "delete from mysql.stats_history use index (idx_create_time) where create_time <= NOW() - INTERVAL %? SECOND limit 50 "
+			_, err = exec.ExecuteInternal(ctx, sql, variable.HistoricalStatsDuration.Load().Seconds())
 			return err
 		}
-		sql = "delete from mysql.stats_history use index (idx_create_time) where create_time <= NOW() - INTERVAL %? SECOND"
-		_, err = exec.ExecuteInternal(ctx, sql, variable.HistoricalStatsDuration.Load().Seconds())
 		logutil.BgLogger().Info("clear outdated historical stats")
-		return err
 	}
 	return nil
 }