plan: push property across semijoin. (pingcap#4083)

executor/join_test.go

@@ -649,6 +649,16 @@ func (s *testSuite) TestInSubquery(c *C) {
 	result.Check(testkit.Rows())
 	result = tk.MustQuery("select * from t1 where a not in (select * from t2 where false)")
 	result.Check(testkit.Rows("1", "2"))
+
+	tk.MustExec("drop table if exists t1, t2")
+	tk.MustExec("create table t1 (a int, key b (a))")
+	tk.MustExec("create table t2 (a int, key b (a))")
+	tk.MustExec("insert into t1 values (1),(2),(2)")
+	tk.MustExec("insert into t2 values (1),(2),(2)")
+	result = tk.MustQuery("select * from t1 where a in (select * from t2) order by a desc")
+	result.Check(testkit.Rows("2", "2", "1"))
+	result = tk.MustQuery("select * from t1 where a in (select count(*) from t2 where t1.a = t2.a) order by a desc")
+	result.Check(testkit.Rows("2", "2", "1"))
 }
 
 func (s *testSuite) TestJoinLeak(c *C) {

plan/dag_plan_test.go

@@ -256,6 +256,11 @@ func (s *testPlanSuite) TestDAGPlanBuilderJoin(c *C) {
 			sql:  "select /*+ TIDB_SMJ(t1,t2)*/ * from t t1, t t2 where t1.a = t2.a order by t2.a",
 			best: "MergeJoin{TableReader(Table(t))->TableReader(Table(t))}(t1.a,t2.a)",
 		},
+		// Test Single Merge Join + Sort + desc.
+		{
+			sql:  "select /*+ TIDB_SMJ(t1,t2)*/ * from t t1, t t2 where t1.a = t2.a order by t2.a desc",
+			best: "MergeJoin{TableReader(Table(t))->TableReader(Table(t))}(t1.a,t2.a)->Sort",
+		},
 		// Test Multi Merge Join.
 		{
 			sql:  "select /*+ TIDB_SMJ(t1,t2,t3)*/ * from t t1, t t2, t t3 where t1.a = t2.a and t2.a = t3.a",
@@ -367,11 +372,16 @@ func (s *testPlanSuite) TestDAGPlanBuilderSubquery(c *C) {
 			sql:  "select * from t where a in (select s.a from t s) order by t.a",
 			best: "SemiJoin{TableReader(Table(t))->TableReader(Table(t))}(test.t.a,s.a)",
 		},
+		// Test Nested sub query.
 		{
-			// Test Nested sub query.
 			sql:  "select * from t where exists (select s.a from t s where s.c in (select c from t as k where k.d = s.d) having sum(s.a) = t.a )",
 			best: "SemiJoin{TableReader(Table(t))->Projection->SemiJoin{TableReader(Table(t))->TableReader(Table(t))}(s.d,k.d)(s.c,k.c)->HashAgg}(cast(test.t.a),sel_agg_1)->Projection",
 		},
+		// Test Semi Join + Order by.
+		{
+			sql:  "select * from t where a in (select a from t) order by b",
+			best: "SemiJoin{TableReader(Table(t))->TableReader(Table(t))}(test.t.a,test.t.a)->Sort",
+		},
 		// Test Apply.
 		{
 			sql:  "select t.c in (select count(*) from t s , t t1 where s.a = t.a and s.a = t1.a) from t",

plan/new_physical_plan_builder.go

@@ -210,6 +210,9 @@ func (p *PhysicalMergeJoin) getChildrenPossibleProps(prop *requiredProp) [][]*re
 	lProp := &requiredProp{taskTp: rootTaskType, cols: p.leftKeys, expectedCnt: math.MaxFloat64}
 	rProp := &requiredProp{taskTp: rootTaskType, cols: p.rightKeys, expectedCnt: math.MaxFloat64}
 	if !prop.isEmpty() {
+		if prop.desc {
+			return nil
+		}
 		if !prop.equal(lProp) && !prop.equal(rProp) {
 			return nil
 		}
@@ -973,19 +976,19 @@ func (p *PhysicalHashJoin) getChildrenPossibleProps(prop *requiredProp) [][]*req
 
 func (p *PhysicalHashSemiJoin) getChildrenPossibleProps(prop *requiredProp) [][]*requiredProp {
 	p.expectedCnt = prop.expectedCnt
-	lProp := &requiredProp{taskTp: rootTaskType, cols: prop.cols, expectedCnt: prop.expectedCnt}
+	lProp := &requiredProp{taskTp: rootTaskType, cols: prop.cols, expectedCnt: prop.expectedCnt, desc: prop.desc}
 	for _, col := range lProp.cols {
 		idx := p.Schema().ColumnIndex(col)
 		if idx == -1 || idx >= p.rightChOffset {
 			return nil
 		}
 	}
-	return [][]*requiredProp{{&requiredProp{taskTp: rootTaskType, expectedCnt: math.MaxFloat64}, &requiredProp{taskTp: rootTaskType, expectedCnt: math.MaxFloat64}}}
+	return [][]*requiredProp{{lProp, &requiredProp{taskTp: rootTaskType, expectedCnt: math.MaxFloat64}}}
 }
 
 func (p *PhysicalApply) getChildrenPossibleProps(prop *requiredProp) [][]*requiredProp {
 	p.expectedCnt = prop.expectedCnt
-	lProp := &requiredProp{taskTp: rootTaskType, cols: prop.cols, expectedCnt: prop.expectedCnt}
+	lProp := &requiredProp{taskTp: rootTaskType, cols: prop.cols, expectedCnt: prop.expectedCnt, desc: prop.desc}
 	for _, col := range lProp.cols {
 		idx := p.Schema().ColumnIndex(col)
 		if idx == -1 || idx >= p.rightChOffset {