planner: fixing wrong result after applying predicate push down for C…

…TEs (pingcap#47891)

planner/core/BUILD.bazel

@@ -42,6 +42,7 @@ go_library(
  "point_get_plan.go",
  "preprocess.go",
  "property_cols_prune.go",
+ "recheck_cte.go",
  "resolve_indices.go",
  "rule_aggregation_elimination.go",
  "rule_aggregation_push_down.go",

planner/core/issuetest/planner_issue_test.go

@@ -90,3 +90,65 @@ func TestIssue46083(t *testing.T) {
  tk.MustExec("CREATE TEMPORARY TABLE v0(v1 int)")
  tk.MustExec("INSERT INTO v0 WITH ta2 AS (TABLE v0) TABLE ta2 FOR UPDATE OF ta2;")
 }
+
+func TestIssue47781(t *testing.T) {
+ store := testkit.CreateMockStore(t)
+ tk := testkit.NewTestKit(t, store)
+ tk.MustExec("use test")
+ tk.MustExec("drop table if exists t, t1, t2")
+ tk.MustExec("create table t (id int,name varchar(10))")
+ tk.MustExec("insert into t values(1,'tt')")
+ tk.MustExec("create table t1(id int,name varchar(10),name1 varchar(10),name2 varchar(10))")
+ tk.MustExec("insert into t1 values(1,'tt','ttt','tttt'),(2,'dd','ddd','dddd')")
+ tk.MustExec("create table t2(id int,name varchar(10),name1 varchar(10),name2 varchar(10),`date1` date)")
+ tk.MustExec("insert into t2 values(1,'tt','ttt','tttt','2099-12-31'),(2,'dd','ddd','dddd','2099-12-31')")
+ tk.MustQuery(`WITH bzzs AS (
+ SELECT 
+ count(1) AS bzn 
+ FROM 
+ t c
+), 
+tmp1 AS (
+ SELECT 
+ t1.* 
+ FROM 
+ t1 
+ LEFT JOIN bzzs ON 1 = 1 
+ WHERE 
+ name IN ('tt') 
+ AND bzn <> 1
+), 
+tmp2 AS (
+ SELECT 
+ tmp1.*, 
+ date('2099-12-31') AS endate 
+ FROM 
+ tmp1
+), 
+tmp3 AS (
+ SELECT 
+ * 
+ FROM 
+ tmp2 
+ WHERE 
+ endate > CURRENT_DATE 
+ UNION ALL 
+ SELECT 
+ '1' AS id, 
+ 'ss' AS name, 
+ 'sss' AS name1, 
+ 'ssss' AS name2, 
+ date('2099-12-31') AS endate 
+ FROM 
+ bzzs t1 
+ WHERE 
+ bzn = 1
+) 
+SELECT 
+ c2.id, 
+ c3.id 
+FROM 
+ t2 db 
+ LEFT JOIN tmp3 c2 ON c2.id = '1' 
+ LEFT JOIN tmp3 c3 ON c3.id = '1';`).Check(testkit.Rows("1 1", "1 1"))
+}

planner/core/logical_plan_builder.go

@@ -4451,7 +4451,7 @@ func (b *PlanBuilder) tryBuildCTE(ctx context.Context, tn *ast.TableName, asName
  LimitEnd: limitEnd, pushDownPredicates: make([]expression.Expression, 0), ColumnMap: make(map[string]*expression.Column)}
  }
  var p LogicalPlan
- lp := LogicalCTE{cteAsName: tn.Name, cteName: tn.Name, cte: cte.cteClass, seedStat: cte.seedStat, isOuterMostCTE: !b.buildingCTE}.Init(b.ctx, b.getSelectOffset())
+ lp := LogicalCTE{cteAsName: tn.Name, cteName: tn.Name, cte: cte.cteClass, seedStat: cte.seedStat}.Init(b.ctx, b.getSelectOffset())
  prevSchema := cte.seedLP.Schema().Clone()
  lp.SetSchema(getResultCTESchema(cte.seedLP.Schema(), b.ctx.GetSessionVars()))
 

planner/core/logical_plans.go

@@ -1964,6 +1964,7 @@ type CTEClass struct {
  // pushDownPredicates may be push-downed by different references.
  pushDownPredicates []expression.Expression
  ColumnMap map[string]*expression.Column
+ isOuterMostCTE bool
 }
 
 const emptyCTEClassSize = int64(unsafe.Sizeof(CTEClass{}))
@@ -1995,11 +1996,10 @@ func (cc *CTEClass) MemoryUsage() (sum int64) {
 type LogicalCTE struct {
  logicalSchemaProducer
 
- cte *CTEClass
- cteAsName model.CIStr
- cteName model.CIStr
- seedStat *property.StatsInfo
- isOuterMostCTE bool
+ cte *CTEClass
+ cteAsName model.CIStr
+ cteName model.CIStr
+ seedStat *property.StatsInfo
 }
 
 // LogicalCTETable is for CTE table

planner/core/optimizer.go

@@ -148,6 +148,9 @@ func BuildLogicalPlanForTest(ctx context.Context, sctx sessionctx.Context, node
  if err != nil {
  return nil, nil, err
  }
+ if logic, ok := p.(LogicalPlan); ok {
+ RecheckCTE(logic)
+ }
  return p, p.OutputNames(), err
 }
 

planner/core/recheck_cte.go

@@ -0,0 +1,53 @@
+// 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 core
+
+import "github.com/pingcap/tidb/planner/funcdep"
+
+// RecheckCTE fills the IsOuterMostCTE field for CTEs.
+// It's a temp solution to before we fully use the Sequence to optimize the CTEs.
+// This func checks whether the CTE is referenced only by the main query or not.
+func RecheckCTE(p LogicalPlan) {
+ visited := funcdep.NewFastIntSet()
+ findCTEs(p, &visited, true)
+}
+
+func findCTEs(
+ p LogicalPlan,
+ visited *funcdep.FastIntSet,
+ isRootTree bool,
+) {
+ if cteReader, ok := p.(*LogicalCTE); ok {
+ cte := cteReader.cte
+ if !isRootTree {
+ // Set it to false since it's referenced by other CTEs.
+ cte.isOuterMostCTE = false
+ }
+ if visited.Has(cte.IDForStorage) {
+ return
+ }
+ visited.Insert(cte.IDForStorage)
+ // Set it when we meet it first time.
+ cte.isOuterMostCTE = isRootTree
+ findCTEs(cte.seedPartLogicalPlan, visited, false)
+ if cte.recursivePartLogicalPlan != nil {
+ findCTEs(cte.recursivePartLogicalPlan, visited, false)
+ }
+ return
+ }
+ for _, child := range p.Children() {
+ findCTEs(child, visited, isRootTree)
+ }
+}

planner/core/rule_predicate_push_down.go

@@ -990,7 +990,7 @@ func (p *LogicalCTE) PredicatePushDown(predicates []expression.Expression, _ *lo
  // Doesn't support recursive CTE yet.
  return predicates, p.self
  }
- if !p.isOuterMostCTE {
+ if !p.cte.isOuterMostCTE {
  return predicates, p.self
  }
  pushedPredicates := make([]expression.Expression, len(predicates))

planner/optimize.go

@@ -407,6 +407,8 @@ func optimize(ctx context.Context, sctx sessionctx.Context, node ast.Node, is in
  return p, names, 0, nil
  }
 
+ core.RecheckCTE(logic)
+
  // Handle the logical plan statement, use cascades planner if enabled.
  if sctx.GetSessionVars().GetEnableCascadesPlanner() {
  finalPlan, cost, err := cascades.DefaultOptimizer.FindBestPlan(sctx, logic)