planner: allow to use dynamic mode to access partitioning tables with…

…out global-stats (#44264) (#44345)

close #44262

planner/core/integration_test.go

@@ -8022,6 +8022,35 @@ func TestExplainAnalyzeDMLCommit(t *testing.T) {
 	tk.MustQuery("select * from t").Check(testkit.Rows())
 }
 
+func TestFixControl44262(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec(`use test`)
+	tk.MustExec(`set tidb_partition_prune_mode='dynamic'`)
+	tk.MustExec(`create table t1 (a int, b int)`)
+	tk.MustExec(`create table t2_part (a int, b int, key(a)) partition by hash(a) partitions 4`)
+
+	testJoin := func(q, join string) {
+		found := false
+		for _, x := range tk.MustQuery(`explain ` + q).Rows() {
+			if strings.Contains(x[0].(string), join) {
+				found = true
+			}
+		}
+		if !found {
+			t.Fatal(q, join)
+		}
+	}
+
+	testJoin(`select /*+ TIDB_INLJ(t2_part@sel_2) */ * from t1 where t1.b<10 and not exists (select 1 from t2_part where t1.a=t2_part.a and t2_part.b<20)`, "HashJoin")
+	tk.MustQuery(`show warnings`).Sort().Check(testkit.Rows(
+		`Warning 1105 disable dynamic pruning due to t2_part has no global stats`,
+		`Warning 1815 Optimizer Hint INL_JOIN or TIDB_INLJ is inapplicable`))
+	tk.MustExec(`set @@tidb_opt_fix_control = "44262:ON"`)
+	testJoin(`select /*+ TIDB_INLJ(t2_part@sel_2) */ * from t1 where t1.b<10 and not exists (select 1 from t2_part where t1.a=t2_part.a and t2_part.b<20)`, "IndexJoin")
+	tk.MustQuery(`show warnings`).Sort().Check(testkit.Rows()) // no warning
+}
+
 func TestIndexJoinRangeFallback(t *testing.T) {
 	store := testkit.CreateMockStore(t)
 	tk := testkit.NewTestKit(t, store)

planner/core/logical_plan_builder.go

@@ -4451,8 +4451,13 @@ func (b *PlanBuilder) buildDataSource(ctx context.Context, tn *ast.TableName, as
 				tblStats := h.GetTableStats(tableInfo)
 				isDynamicEnabled := b.ctx.GetSessionVars().IsDynamicPartitionPruneEnabled()
 				globalStatsReady := tblStats.IsInitialized()
+				allowDynamicWithoutStats := false
+				fixValue, ok := b.ctx.GetSessionVars().GetOptimizerFixControlValue(variable.TiDBOptFixControl44262)
+				if ok && variable.TiDBOptOn(fixValue) {
+					allowDynamicWithoutStats = true
+				}
 				// If dynamic partition prune isn't enabled or global stats is not ready, we won't enable dynamic prune mode in query
-				usePartitionProcessor := !isDynamicEnabled || !globalStatsReady
+				usePartitionProcessor := !isDynamicEnabled || (!globalStatsReady && !allowDynamicWithoutStats)
 
 				failpoint.Inject("forceDynamicPrune", func(val failpoint.Value) {
 					if val.(bool) {

sessionctx/variable/session.go

@@ -1325,6 +1325,25 @@ type SessionVars struct {
 
 	// EnableINLJoinInnerMultiPattern indicates whether enable multi pattern for index join inner side
 	EnableINLJoinInnerMultiPattern bool
+
+	// OptimizerFixControl control some details of the optimizer behavior through the tidb_opt_fix_control variable.
+	OptimizerFixControl map[uint64]string
+}
+
+var (
+	// variables below are for the optimizer fix control.
+
+	// TiDBOptFixControl44262 controls whether to allow to use dynamic-mode to access partitioning tables without global-stats (#44262).
+	TiDBOptFixControl44262 uint64 = 44262
+)
+
+// GetOptimizerFixControlValue returns the specified value of the optimizer fix control.
+func (s *SessionVars) GetOptimizerFixControlValue(key uint64) (value string, exist bool) {
+	if s.OptimizerFixControl == nil {
+		return "", false
+	}
+	value, exist = s.OptimizerFixControl[key]
+	return
 }
 
 // GetNewChunkWithCapacity Attempt to request memory from the chunk pool

sessionctx/variable/sysvar.go

@@ -2260,6 +2260,34 @@ var defaultSysVars = []*SysVar{
 			return BoolToOnOff(s.EnableINLJoinInnerMultiPattern), nil
 		},
 	},
+	{Scope: ScopeGlobal | ScopeSession, Name: TiDBOptFixControl, Value: "", Type: TypeStr, IsHintUpdatable: true,
+		SetSession: func(s *SessionVars, val string) error {
+			newMap := make(map[uint64]string)
+			for _, singleFixCtrl := range strings.Split(val, ",") {
+				if len(singleFixCtrl) == 0 {
+					continue
+				}
+				colonIdx := strings.Index(singleFixCtrl, ":")
+				if colonIdx < 0 {
+					return errors.New("invalid fix control: colon not found")
+				}
+				k := strings.TrimSpace(singleFixCtrl[0:colonIdx])
+				v := strings.TrimSpace(singleFixCtrl[colonIdx+1:])
+				num, err := strconv.ParseUint(k, 10, 64)
+				if err != nil {
+					return err
+				}
+				originalV, ok := newMap[num]
+				if ok {
+					s.StmtCtx.AppendWarning(
+						errors.Errorf("found repeated fix control: %d:%s is overwritten with %s", num, originalV, v))
+				}
+				newMap[num] = v
+			}
+			s.OptimizerFixControl = newMap
+			return nil
+		},
+	},
 }
 
 // FeedbackProbability points to the FeedbackProbability in statistics package.

sessionctx/variable/tidb_vars.go

@@ -795,6 +795,9 @@ const (
 
 	// TiDBEnableINLJoinInnerMultiPattern indicates whether enable multi pattern for inner side of inl join
 	TiDBEnableINLJoinInnerMultiPattern = "tidb_enable_inl_join_inner_multi_pattern"
+
+	// TiDBOptFixControl makes the user able to control some details of the optimizer behavior.
+	TiDBOptFixControl = "tidb_opt_fix_control"
 )
 
 // TiDB vars that have only global scope