planner: fix column pruning bug for Apply and Join (#24369) (#24437)

pingcap · May 26, 2021 · 25b4276 · 25b4276
1 parent 11977a2
commit 25b4276
Show file tree

Hide file tree

Showing 4 changed files with 87 additions and 0 deletions.
diff --git a/planner/core/integration_test.go b/planner/core/integration_test.go
@@ -2870,6 +2870,35 @@ func (s *testIntegrationSuite) TestReorderSimplifiedOuterJoins(c *C) {
 	}
 }
 
+// Apply operator may got panic because empty Projection is eliminated.
+func (s *testIntegrationSerialSuite) TestIssue23887(c *C) {
+	tk := testkit.NewTestKit(c, s.store)
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t;")
+	tk.MustExec("create table t(a int, b int);")
+	tk.MustExec("insert into t values(1, 2), (3, 4);")
+	var input []string
+	var output []struct {
+		SQL  string
+		Plan []string
+		Res  []string
+	}
+	s.testData.GetTestCases(c, &input, &output)
+	for i, tt := range input {
+		s.testData.OnRecord(func() {
+			output[i].SQL = tt
+			output[i].Plan = s.testData.ConvertRowsToStrings(tk.MustQuery("explain format = 'brief' " + tt).Rows())
+			output[i].Res = s.testData.ConvertRowsToStrings(tk.MustQuery(tt).Sort().Rows())
+		})
+		tk.MustQuery("explain format = 'brief' " + tt).Check(testkit.Rows(output[i].Plan...))
+		tk.MustQuery(tt).Sort().Check(testkit.Rows(output[i].Res...))
+	}
+
+	tk.MustExec("drop table if exists t1;")
+	tk.MustExec("create table t1 (c1 int primary key, c2 int, c3 int, index c2 (c2));")
+	tk.MustQuery("select count(1) from (select count(1) from (select * from t1 where c3 = 100) k) k2;").Check(testkit.Rows("1"))
+}
+
 func (s *testIntegrationSerialSuite) TestDeleteStmt(c *C) {
 	tk := testkit.NewTestKit(c, s.store)
 	tk.MustExec("use test")

diff --git a/planner/core/rule_column_pruning.go b/planner/core/rule_column_pruning.go
@@ -314,11 +314,13 @@ func (p *LogicalJoin) PruneColumns(parentUsedCols []*expression.Column) error {
 	if err != nil {
 		return err
 	}
+	addConstOneForEmptyProjection(p.children[0])
 
 	err = p.children[1].PruneColumns(rightCols)
 	if err != nil {
 		return err
 	}
+	addConstOneForEmptyProjection(p.children[1])
 
 	p.mergeSchema()
 	if p.JoinType == LeftOuterSemiJoin || p.JoinType == AntiLeftOuterSemiJoin {
@@ -337,6 +339,7 @@ func (la *LogicalApply) PruneColumns(parentUsedCols []*expression.Column) error
 	if err != nil {
 		return err
 	}
+	addConstOneForEmptyProjection(la.children[1])
 
 	la.CorCols = extractCorColumnsBySchema4LogicalPlan(la.children[1], la.children[0].Schema())
 	for _, col := range la.CorCols {
@@ -347,6 +350,7 @@ func (la *LogicalApply) PruneColumns(parentUsedCols []*expression.Column) error
 	if err != nil {
 		return err
 	}
+	addConstOneForEmptyProjection(la.children[0])
 
 	la.mergeSchema()
 	return nil
@@ -431,3 +435,25 @@ func (p *LogicalLimit) PruneColumns(parentUsedCols []*expression.Column) error {
 func (*columnPruner) name() string {
 	return "column_prune"
 }
+
+// By add const one, we can avoid empty Projection is eliminated.
+// Because in some cases, Projectoin cannot be eliminated even its output is empty.
+func addConstOneForEmptyProjection(p LogicalPlan) {
+	proj, ok := p.(*LogicalProjection)
+	if !ok {
+		return
+	}
+	if proj.Schema().Len() != 0 {
+		return
+	}
+
+	constOne := expression.NewOne()
+	proj.schema.Append(&expression.Column{
+		UniqueID: proj.ctx.GetSessionVars().AllocPlanColumnID(),
+		RetType:  constOne.GetType(),
+	})
+	proj.Exprs = append(proj.Exprs, &expression.Constant{
+		Value:   constOne.Value,
+		RetType: constOne.GetType(),
+	})
+}
diff --git a/planner/core/testdata/integration_serial_suite_in.json b/planner/core/testdata/integration_serial_suite_in.json
@@ -255,6 +255,12 @@
       "desc format = 'brief' select * from (select id from t group by id) C join (select sum(b),id from (select t.id, t1.id as b from t join (select id, count(*) as c from t group by id) t1 on t.id=t1.id)A group by id)B on C.id=b.id"
     ]
   },
+  {
+      "name": "TestIssue23887",
+      "cases": [
+          "select (2) in (select b from t) from (select t.a < (select t.a from t t1 limit 1) from t) t"
+      ]
+  },
   {
     "name": "TestMergeContinuousSelections",
     "cases": [

diff --git a/planner/core/testdata/integration_serial_suite_out.json b/planner/core/testdata/integration_serial_suite_out.json
@@ -2283,6 +2283,32 @@
       }
     ]
   },
+  {
+    "Name": "TestIssue23887",
+    "Cases": [
+      {
+        "SQL": "select (2) in (select b from t) from (select t.a < (select t.a from t t1 limit 1) from t) t",
+        "Plan": [
+          "HashJoin 10000.00 root  CARTESIAN left outer semi join, other cond:eq(2, test.t.b)",
+          "├─TableReader(Build) 10000.00 root  data:TableFullScan",
+          "│ └─TableFullScan 10000.00 cop[tikv] table:t keep order:false, stats:pseudo",
+          "└─Projection(Probe) 10000.00 root  1->Column#27",
+          "  └─Apply 10000.00 root  CARTESIAN left outer join",
+          "    ├─TableReader(Build) 10000.00 root  data:TableFullScan",
+          "    │ └─TableFullScan 10000.00 cop[tikv] table:t keep order:false, stats:pseudo",
+          "    └─Projection(Probe) 1.00 root  1->Column#25",
+          "      └─Limit 1.00 root  offset:0, count:1",
+          "        └─TableReader 1.00 root  data:Limit",
+          "          └─Limit 1.00 cop[tikv]  offset:0, count:1",
+          "            └─TableFullScan 1.00 cop[tikv] table:t1 keep order:false, stats:pseudo"
+        ],
+        "Res": [
+          "1",
+          "1"
+        ]
+      }
+    ]
+  },
   {
     "Name": "TestMergeContinuousSelections",
     "Cases": [