planner: change more conditions that are always false to dual (#59199)

close #51446

pkg/executor/prepared_test.go

@@ -55,7 +55,7 @@ func TestPreparedNullParam(t *testing.T) {
 		ps := []*util.ProcessInfo{tkProcess}
 		tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
 		tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).Check(testkit.Rows(
-			"TableDual_5 0.00 root  rows:0"))
+			"TableDual_6 0.00 root  rows:0"))
 	}
 }
 

pkg/expression/util.go

@@ -2162,3 +2162,19 @@ func binaryDurationWithMS(pos int, paramValues []byte,
 	pos += 4
 	return pos, fmt.Sprintf("%s.%06d", dur, microSecond)
 }
+
+// IsConstNull is used to check whether the expression is a constant null expression.
+// For example, `1 > NULL` is a constant null expression.
+// Now we just assume that the first argrument is a column,
+// the second argument is a constant null.
+func IsConstNull(expr Expression) bool {
+	if e, ok := expr.(*ScalarFunction); ok {
+		switch e.FuncName.L {
+		case ast.LT, ast.LE, ast.GT, ast.GE, ast.EQ, ast.NE:
+			if constExpr, ok := e.GetArgs()[1].(*Constant); ok && constExpr.Value.IsNull() && constExpr.DeferredExpr == nil {
+				return true
+			}
+		}
+	}
+	return false
+}

pkg/planner/core/casetest/rule/BUILD.bazel

@@ -4,6 +4,7 @@ go_test(
     name = "rule_test",
     timeout = "short",
     srcs = [
+        "dual_test.go",
         "main_test.go",
         "rule_derive_topn_from_window_test.go",
         "rule_inject_extra_projection_test.go",
@@ -13,7 +14,7 @@ go_test(
     ],
     data = glob(["testdata/**"]),
     flaky = True,
-    shard_count = 8,
+    shard_count = 9,
     deps = [
         "//pkg/domain",
         "//pkg/expression",

pkg/planner/core/casetest/rule/dual_test.go

@@ -0,0 +1,47 @@
+// Copyright 2023 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package rule
+
+import (
+	"testing"
+
+	"github.com/pingcap/tidb/pkg/testkit"
+)
+
+func TestDual(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.MustExec("use test")
+	tk.MustExec("CREATE TABLE t (id INT PRIMARY KEY AUTO_INCREMENT,d INT);")
+	tk.MustQuery("explain select a from (select d as a from t where d = 0) k where k.a = 5").Check(testkit.Rows(
+		"TableDual_8 0.00 root  rows:0"))
+	tk.MustQuery("select a from (select d as a from t where d = 0) k where k.a = 5").Check(testkit.Rows())
+	tk.MustQuery("explain select a from (select 1+2 as a from t where d = 0) k where k.a = 5").Check(testkit.Rows(
+		"Projection_8 0.00 root  3->Column#3",
+		"└─TableDual_9 0.00 root  rows:0"))
+	tk.MustQuery("select a from (select 1+2 as a from t where d = 0) k where k.a = 5").Check(testkit.Rows())
+	tk.MustQuery("explain select * from t where d != null;").Check(testkit.Rows(
+		"TableDual_6 0.00 root  rows:0"))
+	tk.MustQuery("explain select * from t where d > null;").Check(testkit.Rows(
+		"TableDual_6 0.00 root  rows:0"))
+	tk.MustQuery("explain select * from t where d >= null;").Check(testkit.Rows(
+		"TableDual_6 0.00 root  rows:0"))
+	tk.MustQuery("explain select * from t where d < null;").Check(testkit.Rows(
+		"TableDual_6 0.00 root  rows:0"))
+	tk.MustQuery("explain select * from t where d <= null;").Check(testkit.Rows(
+		"TableDual_6 0.00 root  rows:0"))
+	tk.MustQuery("explain select * from t where d = null;").Check(testkit.Rows(
+		"TableDual_6 0.00 root  rows:0"))
+}

pkg/planner/core/casetest/rule/testdata/outer2inner_out.json

@@ -161,14 +161,7 @@
       {
         "SQL": "select * from t3 as t1 left join t3 as t2 on t1.c3 = t2.c3 where t2.b3 != NULL; -- self join",
         "Plan": [
-          "Projection 0.00 root  test.t3.a3, test.t3.b3, test.t3.c3, test.t3.a3, test.t3.b3, test.t3.c3",
-          "└─HashJoin 0.00 root  inner join, equal:[eq(test.t3.c3, test.t3.c3)]",
-          "  ├─TableReader(Build) 0.00 root  data:Selection",
-          "  │ └─Selection 0.00 cop[tikv]  ne(test.t3.b3, NULL), not(isnull(test.t3.c3))",
-          "  │   └─TableFullScan 10000.00 cop[tikv] table:t2 keep order:false, stats:pseudo",
-          "  └─TableReader(Probe) 9990.00 root  data:Selection",
-          "    └─Selection 9990.00 cop[tikv]  not(isnull(test.t3.c3))",
-          "      └─TableFullScan 10000.00 cop[tikv] table:t1 keep order:false, stats:pseudo"
+          "TableDual 0.00 root  rows:0"
         ]
       },
       {
@@ -434,13 +427,7 @@
       {
         "SQL": "select * from t3 as t1 left join t3 as t2 on t1.c3 = t2.c3 where t1.b3 != NULL -- negative case with self join",
         "Plan": [
-          "HashJoin 0.00 root  left outer join, left side:TableReader, equal:[eq(test.t3.c3, test.t3.c3)]",
-          "├─TableReader(Build) 0.00 root  data:Selection",
-          "│ └─Selection 0.00 cop[tikv]  ne(test.t3.b3, NULL)",
-          "│   └─TableFullScan 10000.00 cop[tikv] table:t1 keep order:false, stats:pseudo",
-          "└─TableReader(Probe) 9990.00 root  data:Selection",
-          "  └─Selection 9990.00 cop[tikv]  not(isnull(test.t3.c3))",
-          "    └─TableFullScan 10000.00 cop[tikv] table:t2 keep order:false, stats:pseudo"
+          "TableDual 0.00 root  rows:0"
         ]
       },
       {

pkg/planner/core/issuetest/main_test.go

@@ -30,6 +30,7 @@ func TestMain(m *testing.M) {
 	testsetup.SetupForCommonTest()
 	flag.Parse()
 	opts := []goleak.Option{
+		goleak.IgnoreTopFunction("go.opencensus.io/stats/view.(*worker).start"),
 		goleak.IgnoreTopFunction("github.com/golang/glog.(*fileSink).flushDaemon"),
 		goleak.IgnoreTopFunction("github.com/bazelbuild/rules_go/go/tools/bzltestutil.RegisterTimeoutHandler.func1"),
 		goleak.IgnoreTopFunction("github.com/lestrrat-go/httprc.runFetchWorker"),

pkg/planner/core/logical_plans_test.go

@@ -330,7 +330,7 @@ func TestAntiSemiJoinConstFalse(t *testing.T) {
 	}{
 		{
 			sql:      "select a from t t1 where not exists (select a from t t2 where t1.a = t2.a and t2.b = 1 and t2.b = 2)",
-			best:     "Join{DataScan(t1)->DataScan(t2)}(test.t.a,test.t.a)->Projection",
+			best:     "Join{DataScan(t1)->Dual}(test.t.a,test.t.a)->Projection",
 			joinType: "anti semi join",
 		},
 	}

pkg/planner/core/operator/logicalop/BUILD.bazel

@@ -4,6 +4,7 @@ go_library(
     name = "logicalop",
     srcs = [
         "base_logical_plan.go",
+        "expression_util.go",
         "hash64_equals_generated.go",
         "logical_aggregation.go",
         "logical_apply.go",

pkg/planner/core/operator/logicalop/expression_util.go

@@ -0,0 +1,52 @@
+// Copyright 2025 PingCAP, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package logicalop
+
+import (
+	"github.com/pingcap/tidb/pkg/expression"
+	"github.com/pingcap/tidb/pkg/planner/core/base"
+)
+
+// Conds2TableDual builds a LogicalTableDual if cond is constant false or null.
+func Conds2TableDual(p base.LogicalPlan, conds []expression.Expression) base.LogicalPlan {
+	for _, cond := range conds {
+		if expression.IsConstNull(cond) {
+			if expression.MaybeOverOptimized4PlanCache(p.SCtx().GetExprCtx(), conds) {
+				return nil
+			}
+			dual := LogicalTableDual{}.Init(p.SCtx(), p.QueryBlockOffset())
+			dual.SetSchema(p.Schema())
+			return dual
+		}
+	}
+	if len(conds) != 1 {
+		return nil
+	}
+
+	con, ok := conds[0].(*expression.Constant)
+	if !ok {
+		return nil
+	}
+	sc := p.SCtx().GetSessionVars().StmtCtx
+	if expression.MaybeOverOptimized4PlanCache(p.SCtx().GetExprCtx(), []expression.Expression{con}) {
+		return nil
+	}
+	if isTrue, err := con.Value.ToBool(sc.TypeCtxOrDefault()); (err == nil && isTrue == 0) || con.Value.IsNull() {
+		dual := LogicalTableDual{}.Init(p.SCtx(), p.QueryBlockOffset())
+		dual.SetSchema(p.Schema())
+		return dual
+	}
+	return nil
+}

pkg/planner/core/operator/logicalop/logical_datasource.go

@@ -155,6 +155,11 @@ func (ds *DataSource) PredicatePushDown(predicates []expression.Expression, opt
 	// TODO: remove it to the place building logical plan
 	predicates = utilfuncp.AddPrefix4ShardIndexes(ds, ds.SCtx(), predicates)
 	ds.AllConds = predicates
+	dual := Conds2TableDual(ds, ds.AllConds)
+	if dual != nil {
+		AppendTableDualTraceStep(ds, dual, predicates, opt)
+		return nil, dual
+	}
 	ds.PushedDownConds, predicates = expression.PushDownExprs(util.GetPushDownCtx(ds.SCtx()), predicates, kv.UnSpecified)
 	appendDataSourcePredicatePushDownTraceStep(ds, opt)
 	return predicates, ds

pkg/planner/core/operator/logicalop/logical_join.go

@@ -1871,27 +1871,6 @@ func deriveNotNullExpr(ctx base.PlanContext, expr expression.Expression, schema
 	return nil
 }
 
-// Conds2TableDual builds a LogicalTableDual if cond is constant false or null.
-func Conds2TableDual(p base.LogicalPlan, conds []expression.Expression) base.LogicalPlan {
-	if len(conds) != 1 {
-		return nil
-	}
-	con, ok := conds[0].(*expression.Constant)
-	if !ok {
-		return nil
-	}
-	sc := p.SCtx().GetSessionVars().StmtCtx
-	if expression.MaybeOverOptimized4PlanCache(p.SCtx().GetExprCtx(), []expression.Expression{con}) {
-		return nil
-	}
-	if isTrue, err := con.Value.ToBool(sc.TypeCtxOrDefault()); (err == nil && isTrue == 0) || con.Value.IsNull() {
-		dual := LogicalTableDual{}.Init(p.SCtx(), p.QueryBlockOffset())
-		dual.SetSchema(p.Schema())
-		return dual
-	}
-	return nil
-}
-
 // BuildLogicalJoinSchema builds the schema for join operator.
 func BuildLogicalJoinSchema(joinType JoinType, join base.LogicalPlan) *expression.Schema {
 	leftSchema := join.Children()[0].Schema()

pkg/planner/core/testdata/plan_suite_unexported_out.json

@@ -67,8 +67,8 @@
       "Join{DataScan(a)->DataScan(b)}(test.t.a,test.t.a)->Aggr(count(1))->Projection",
       "DataScan(t)->Projection->Projection",
       "DataScan(t)->Projection->Projection",
-      "DataScan(t)->Projection->Projection",
-      "DataScan(t)->Projection->Projection",
+      "Dual->Projection->Projection",
+      "Dual->Projection->Projection",
       "Join{DataScan(ta)->DataScan(tb)}(test.t.d,test.t.b)(test.t.a,test.t.c)->Projection",
       "Join{DataScan(t1)->DataScan(t2)}(test.t.a,test.t.b)(test.t.d,test.t.d)->Projection",
       "Join{DataScan(ta)->DataScan(tb)}(test.t.d,test.t.d)->Projection",

tests/integrationtest/r/executor/executor.result

@@ -2765,47 +2765,35 @@ create table t (c1 year(4), c2 int, key(c1));
 insert into t values(2001, 1);
 explain format = 'brief' select t1.c1, t2.c1 from t as t1 inner join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 id	estRows	task	access object	operator info
-MergeJoin	0.00	root		inner join, left key:executor__executor.t.c1, right key:executor__executor.t.c1
-├─TableDual(Build)	0.00	root		rows:0
-└─TableDual(Probe)	0.00	root		rows:0
+TableDual	0.00	root		rows:0
 select t1.c1, t2.c1 from t as t1 inner join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 c1	c1
 explain format = 'brief' select * from t as t1 inner join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 id	estRows	task	access object	operator info
-MergeJoin	0.00	root		inner join, left key:executor__executor.t.c1, right key:executor__executor.t.c1
-├─TableDual(Build)	0.00	root		rows:0
-└─TableDual(Probe)	0.00	root		rows:0
+TableDual	0.00	root		rows:0
 select * from t as t1 inner join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 c1	c2	c1	c2
 explain format = 'brief' select count(*) from t as t1 inner join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 id	estRows	task	access object	operator info
 StreamAgg	1.00	root		funcs:count(1)->Column#7
-└─MergeJoin	0.00	root		inner join, left key:executor__executor.t.c1, right key:executor__executor.t.c1
-  ├─TableDual(Build)	0.00	root		rows:0
-  └─TableDual(Probe)	0.00	root		rows:0
+└─TableDual	0.00	root		rows:0
 select count(*) from t as t1 inner join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 count(*)
 0
 explain format = 'brief' select t1.c1, t2.c1 from t as t1 left join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 id	estRows	task	access object	operator info
-MergeJoin	0.00	root		left outer join, left side:TableDual, left key:executor__executor.t.c1, right key:executor__executor.t.c1
-├─TableDual(Build)	0.00	root		rows:0
-└─TableDual(Probe)	0.00	root		rows:0
+TableDual	0.00	root		rows:0
 select t1.c1, t2.c1 from t as t1 left join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 c1	c1
 explain format = 'brief' select * from t as t1 left join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 id	estRows	task	access object	operator info
-MergeJoin	0.00	root		left outer join, left side:TableDual, left key:executor__executor.t.c1, right key:executor__executor.t.c1
-├─TableDual(Build)	0.00	root		rows:0
-└─TableDual(Probe)	0.00	root		rows:0
+TableDual	0.00	root		rows:0
 select * from t as t1 left join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 c1	c2	c1	c2
 explain format = 'brief' select count(*) from t as t1 left join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 id	estRows	task	access object	operator info
 StreamAgg	1.00	root		funcs:count(1)->Column#7
-└─MergeJoin	0.00	root		left outer join, left side:TableDual, left key:executor__executor.t.c1, right key:executor__executor.t.c1
-  ├─TableDual(Build)	0.00	root		rows:0
-  └─TableDual(Probe)	0.00	root		rows:0
+└─TableDual	0.00	root		rows:0
 select count(*) from t as t1 left join t as t2 on t1.c1 = t2.c1 where t1.c1 != NULL;
 count(*)
 0

tests/integrationtest/r/planner/core/casetest/index/index.result

@@ -134,7 +134,7 @@ Selection_5	0.00	root		json_overlaps(planner__core__casetest__index__index.t2.a,
   └─TableRowIDScan_8(Probe)	0.00	cop[tikv]	table:t2	keep order:false, stats:pseudo
 explain select /*+ use_index_merge(t2, idx2, idx) */ * from t2 where 1 member of (a) and c=1 and c=2; -- 6: AND index merge from multi complicated mv indexes (empty range);
 id	estRows	task	access object	operator info
-TableDual_5	0.00	root		rows:0
+TableDual_6	0.00	root		rows:0
 drop table if exists t;
 create table t(a int, b int, c int, unique index(a), unique index(b), primary key(c));
 explain format = 'brief' select /*+ USE_INDEX_MERGE(t, a, b) */ * from t where a = 1 or b = 2;

tests/integrationtest/r/planner/core/casetest/predicate_simplification.result

@@ -122,14 +122,10 @@ Selection	12.80	root		gt(Column#4, 100)
         └─TableFullScan	10000.00	cop[tikv]	table:ts	keep order:false, stats:pseudo
 explain format = 'brief' select f from t where f <> NULL  and f in (1,2,3) -- Special case of NULL with no simplification.;
 id	estRows	task	access object	operator info
-TableReader	0.00	root		data:Selection
-└─Selection	0.00	cop[tikv]		in(planner__core__casetest__predicate_simplification.t.f, 1, 2, 3), ne(planner__core__casetest__predicate_simplification.t.f, NULL)
-  └─TableFullScan	10000.00	cop[tikv]	table:t	keep order:false, stats:pseudo
+TableDual	0.00	root		rows:0
 explain format = 'brief' select f from t where f != NULL  and f in (NULL,2,3) -- Special case of NULL with no simplification.;
 id	estRows	task	access object	operator info
-TableReader	0.00	root		data:Selection
-└─Selection	0.00	cop[tikv]		in(planner__core__casetest__predicate_simplification.t.f, NULL, 2, 3), ne(planner__core__casetest__predicate_simplification.t.f, NULL)
-  └─TableFullScan	10000.00	cop[tikv]	table:t	keep order:false, stats:pseudo
+TableDual	0.00	root		rows:0
 drop table if exists dt;
 drop table if exists it;
 CREATE TABLE `dt` (

tests/integrationtest/r/tpch.result

@@ -710,20 +710,8 @@ and n_name = 'MOZAMBIQUE'
 order by
 value desc;
 id	estRows	task	access object	operator info
-Projection	1283496.34	root		tpch50.partsupp.ps_partkey, Column#35->Column#58
-└─Sort	1283496.34	root		Column#35:desc
-  └─Selection	1283496.34	root		gt(Column#35, NULL)
-    └─HashAgg	1604370.43	root		group by:Column#60, funcs:sum(Column#59)->Column#35, funcs:firstrow(Column#60)->tpch50.partsupp.ps_partkey
-      └─Projection	1604370.43	root		mul(tpch50.partsupp.ps_supplycost, cast(tpch50.partsupp.ps_availqty, decimal(10,0) BINARY))->Column#59, tpch50.partsupp.ps_partkey->Column#60
-        └─HashJoin	1604370.43	root		inner join, equal:[eq(tpch50.supplier.s_suppkey, tpch50.partsupp.ps_suppkey)]
-          ├─HashJoin(Build)	19999.44	root		inner join, equal:[eq(tpch50.nation.n_nationkey, tpch50.supplier.s_nationkey)]
-          │ ├─TableReader(Build)	1.00	root		data:Selection
-          │ │ └─Selection	1.00	cop[tikv]		eq(tpch50.nation.n_name, "MOZAMBIQUE")
-          │ │   └─TableFullScan	25.00	cop[tikv]	table:nation	keep order:false
-          │ └─TableReader(Probe)	500000.00	root		data:TableFullScan
-          │   └─TableFullScan	500000.00	cop[tikv]	table:supplier	keep order:false
-          └─TableReader(Probe)	40000000.00	root		data:TableFullScan
-            └─TableFullScan	40000000.00	cop[tikv]	table:partsupp	keep order:false
+Projection	0.00	root		tpch50.partsupp.ps_partkey, Column#35->Column#58
+└─TableDual	0.00	root		rows:0
 /*
 Q12 Shipping Modes and Order Priority Query
 This query determines whether selecting less expensive modes of shipping is negatively affecting the critical-priority
@@ -1292,10 +1280,5 @@ id	estRows	task	access object	operator info
 Sort	1.00	root		Column#31
 └─Projection	1.00	root		Column#31, Column#32, Column#33
   └─HashAgg	1.00	root		group by:Column#36, funcs:count(1)->Column#32, funcs:sum(Column#35)->Column#33, funcs:firstrow(Column#36)->Column#31
-    └─Projection	0.64	root		tpch50.customer.c_acctbal->Column#35, substring(tpch50.customer.c_phone, 1, 2)->Column#36
-      └─HashJoin	0.64	root		anti semi join, left side:TableReader, equal:[eq(tpch50.customer.c_custkey, tpch50.orders.o_custkey)]
-        ├─TableReader(Build)	0.80	root		data:Selection
-        │ └─Selection	0.80	cop[tikv]		gt(tpch50.customer.c_acctbal, NULL), in(substring(tpch50.customer.c_phone, 1, 2), "20", "40", "22", "30", "39", "42", "21")
-        │   └─TableFullScan	7500000.00	cop[tikv]	table:customer	keep order:false
-        └─TableReader(Probe)	75000000.00	root		data:TableFullScan
-          └─TableFullScan	75000000.00	cop[tikv]	table:orders	keep order:false
+    └─Projection	0.00	root		tpch50.customer.c_acctbal->Column#35, substring(tpch50.customer.c_phone, 1, 2)->Column#36
+      └─TableDual	0.00	root		rows:0