planner: fix wrong PointGet / TableDual plan reused in plan cache (#2…

…3238)

executor/explainfor_test.go

@@ -479,7 +479,4 @@ func (s *testPrepareSerialSuite) TestPointGetUserVarPlanCache(c *C) {
 	tk.MustQuery("execute stmt using @a").Check(testkit.Rows(
 		"2 4 2 2",
 	))
-	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows(
-		"1",
-	))
 }

executor/prepared_test.go

@@ -254,7 +254,6 @@ func (s *testSerialSuite) TestPlanCacheClusterIndex(c *C) {
 	tk.MustExec(`set @v1 = 'a', @v2 = 'b'`)
 	tk.MustQuery(`execute stmt1 using @v1`).Check(testkit.Rows("a 1 a 1"))
 	tk.MustQuery(`execute stmt1 using @v2`).Check(testkit.Rows("b 2 b 2"))
-	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
 
 	// case 2:
 	tk.MustExec(`drop table if exists ta, tb`)
@@ -266,7 +265,6 @@ func (s *testSerialSuite) TestPlanCacheClusterIndex(c *C) {
 	tk.MustExec(`set @v1 = 'a', @v2 = 'b'`)
 	tk.MustQuery(`execute stmt1 using @v1`).Check(testkit.Rows("a 1 1 1"))
 	tk.MustQuery(`execute stmt1 using @v2`).Check(testkit.Rows("b 2 2 2"))
-	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
 	tk.MustQuery(`execute stmt1 using @v2`).Check(testkit.Rows("b 2 2 2"))
 	tkProcess = tk.Se.ShowProcess()
 	ps = []*util.ProcessInfo{tkProcess}

executor/seqtest/prepared_test.go

@@ -490,14 +490,14 @@ func (s *seqTestSuite) TestPreparedInsert(c *C) {
 			err = counter.Write(pb)
 			c.Assert(err, IsNil)
 			hit := pb.GetCounter().GetValue()
-			c.Check(hit, Equals, float64(3))
+			c.Check(hit, Equals, float64(2))
 		}
 		tk.MustExec(`set @a=3; execute stmt_insert_select using @a;`)
 		if flag {
 			err = counter.Write(pb)
 			c.Assert(err, IsNil)
 			hit := pb.GetCounter().GetValue()
-			c.Check(hit, Equals, float64(4))
+			c.Check(hit, Equals, float64(2))
 		}
 
 		result = tk.MustQuery("select id, c1 from prepare_test where id = ?", 101)

planner/core/common_plans.go

@@ -425,6 +425,9 @@ REBUILD:
 // short paths for these executions, currently "point select" and "point update"
 func (e *Execute) tryCachePointPlan(ctx context.Context, sctx sessionctx.Context,
 	preparedStmt *CachedPrepareStmt, is infoschema.InfoSchema, p Plan) error {
+	if sctx.GetSessionVars().StmtCtx.OptimDependOnMutableConst {
+		return nil
+	}
 	var (
 		prepared = preparedStmt.PreparedAst
 		ok       bool

planner/core/find_best_task.go

@@ -528,7 +528,7 @@ func (ds *DataSource) skylinePruning(prop *property.PhysicalProperty) []*candida
 			continue
 		}
 		// if we already know the range of the scan is empty, just return a TableDual
-		if len(path.Ranges) == 0 && !ds.ctx.GetSessionVars().StmtCtx.UseCache {
+		if len(path.Ranges) == 0 {
 			return []*candidatePath{{path: path}}
 		}
 		if path.StoreType != kv.TiFlash && (prop.TaskTp == property.CopTiFlashLocalReadTaskType || prop.TaskTp == property.CopTiFlashGlobalReadTaskType) {

planner/core/prepare_test.go

@@ -1036,3 +1036,96 @@ func (s *testPlanSerialSuite) TestPlanCacheSnapshot(c *C) {
 	tk.MustQuery("execute stmt using @p").Check(testkit.Rows("1"))
 	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
 }
+
+func (s *testPlanSerialSuite) TestPlanCachePointGetAndTableDual(c *C) {
+	store, _, err := newStoreWithBootstrap()
+	c.Assert(err, IsNil)
+	tk := testkit.NewTestKit(c, store)
+	orgEnable := core.PreparedPlanCacheEnabled()
+	defer func() {
+		store.Close()
+		core.SetPreparedPlanCache(orgEnable)
+	}()
+	core.SetPreparedPlanCache(true)
+
+	tk.Se, err = session.CreateSession4TestWithOpt(store, &session.Opt{
+		PreparedPlanCache: kvcache.NewSimpleLRUCache(100, 0.1, math.MaxUint64),
+	})
+	c.Assert(err, IsNil)
+
+	tk.MustExec("use test")
+	tk.MustExec("drop table if exists t0, t1, t2, t3, t4")
+
+	tk.MustExec("create table t0(c1 varchar(20), c2 varchar(20), c3 bigint(20), primary key(c1, c2))")
+	tk.MustExec("insert into t0 values('0000','7777',1)")
+	tk.MustExec("prepare s0 from 'select * from t0 where c1=? and c2>=? and c2<=?'")
+	tk.MustExec("set @a0='0000', @b0='9999'")
+	// TableDual plan would be built, we should not cache it.
+	tk.MustQuery("execute s0 using @a0, @b0, @a0").Check(testkit.Rows())
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+	// Must not reuse the previous TableDual plan.
+	tk.MustQuery("execute s0 using @a0, @a0, @b0").Check(testkit.Rows("0000 7777 1"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+
+	tk.MustExec("create table t1(c1 varchar(20), c2 varchar(20), c3 bigint(20), primary key(c1, c2))")
+	tk.MustExec("insert into t1 values('0000','7777',1)")
+	tk.MustExec("prepare s1 from 'select * from t1 where c1=? and c2>=? and c2<=?'")
+	tk.MustExec("set @a1='0000', @b1='9999'")
+	// PointGet plan would be built, we should not cache it.
+	tk.MustQuery("execute s1 using @a1, @b1, @b1").Check(testkit.Rows())
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+	// Must not reuse the previous PointGet plan.
+	tk.MustQuery("execute s1 using @a1, @a1, @b1").Check(testkit.Rows("0000 7777 1"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+
+	tk.MustExec("create table t2(c1 bigint(20) primary key, c2 varchar(20))")
+	tk.MustExec("insert into t2 values(1,'7777')")
+	tk.MustExec("prepare s2 from 'select * from t2 where c1>=? and c1<=?'")
+	tk.MustExec("set @a2=0, @b2=9")
+	// PointGet plan would be built, we should not cache it.
+	tk.MustQuery("execute s2 using @a2, @a2").Check(testkit.Rows())
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+	// Must not reuse the previous PointGet plan.
+	tk.MustQuery("execute s2 using @a2, @b2").Check(testkit.Rows("1 7777"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+
+	tk.MustExec("create table t3(c1 int, c2 int, c3 int, unique key(c1), key(c2))")
+	tk.MustExec("insert into t3 values(2,1,1)")
+	tk.MustExec("prepare s3 from 'select /*+ use_index_merge(t3) */ * from t3 where (c1 >= ? and c1 <= ?) or c2 > 1'")
+	tk.MustExec("set @a3=1,@b3=3")
+	// PointGet partial plan would be built, we should not cache it.
+	tk.MustQuery("execute s3 using @a3,@a3").Check(testkit.Rows())
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+	// Must not reuse the previous IndexMerge with partial PointGet plan.
+	tk.MustQuery("execute s3 using @a3,@b3").Check(testkit.Rows("2 1 1"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+
+	tk.MustExec("prepare s3 from 'select /*+ use_index_merge(t3) */ * from t3 where (c1 >= ? and c1 <= ?) or c2 > 1'")
+	tk.MustExec("set @a3=1,@b3=3")
+	// TableDual partial plan would be built, we should not cache it.
+	tk.MustQuery("execute s3 using @b3,@a3").Check(testkit.Rows())
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+	// Must not reuse the previous IndexMerge with partial TableDual plan.
+	tk.MustQuery("execute s3 using @a3,@b3").Check(testkit.Rows("2 1 1"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+
+	tk.MustExec("create table t4(c1 int primary key, c2 int, c3 int, key(c2))")
+	tk.MustExec("insert into t4 values(2,1,1)")
+	tk.MustExec("prepare s4 from 'select /*+ use_index_merge(t4) */ * from t4 where (c1 >= ? and c1 <= ?) or c2 > 1'")
+	tk.MustExec("set @a4=1,@b4=3")
+	// PointGet partial plan would be built, we should not cache it.
+	tk.MustQuery("execute s4 using @a4,@a4").Check(testkit.Rows())
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+	// Must not reuse the previous IndexMerge with partial PointGet plan.
+	tk.MustQuery("execute s4 using @a4,@b4").Check(testkit.Rows("2 1 1"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+
+	tk.MustExec("prepare s4 from 'select /*+ use_index_merge(t4) */ * from t4 where (c1 >= ? and c1 <= ?) or c2 > 1'")
+	tk.MustExec("set @a4=1,@b4=3")
+	// TableDual partial plan would be built, we should not cache it.
+	tk.MustQuery("execute s4 using @b4,@a4").Check(testkit.Rows())
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+	// Must not reuse the previous IndexMerge with partial TableDual plan.
+	tk.MustQuery("execute s4 using @a4,@b4").Check(testkit.Rows("2 1 1"))
+	tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
+}

planner/core/stats.go

@@ -285,6 +285,7 @@ func (ds *DataSource) DeriveStats(childStats []*property.StatsInfo, selfSchema *
 			if noIntervalRanges || len(path.Ranges) == 0 {
 				ds.possibleAccessPaths[0] = path
 				ds.possibleAccessPaths = ds.possibleAccessPaths[:1]
+				ds.ctx.GetSessionVars().StmtCtx.OptimDependOnMutableConst = true
 				break
 			}
 			continue
@@ -294,6 +295,7 @@ func (ds *DataSource) DeriveStats(childStats []*property.StatsInfo, selfSchema *
 		if (noIntervalRanges && path.Index.Unique) || len(path.Ranges) == 0 {
 			ds.possibleAccessPaths[0] = path
 			ds.possibleAccessPaths = ds.possibleAccessPaths[:1]
+			ds.ctx.GetSessionVars().StmtCtx.OptimDependOnMutableConst = true
 			break
 		}
 	}
@@ -506,10 +508,8 @@ func (ds *DataSource) accessPathsForConds(conditions []expression.Expression, us
 				logutil.BgLogger().Debug("can not derive statistics of a path", zap.Error(err))
 				continue
 			}
-			// If `AccessConds` is empty, we ignore the access path.
-			// If the path contains a full range, ignore it also. This can happen when `AccessConds` is constant true, and
-			// it comes from the result of a subquery, so it is not folded.
-			if len(path.AccessConds) == 0 || ranger.HasFullRange(path.Ranges) {
+			// If the path contains a full range, ignore it.
+			if ranger.HasFullRange(path.Ranges) {
 				continue
 			}
 			// If we have point or empty range, just remove other possible paths.
@@ -520,6 +520,7 @@ func (ds *DataSource) accessPathsForConds(conditions []expression.Expression, us
 					results[0] = path
 					results = results[:1]
 				}
+				ds.ctx.GetSessionVars().StmtCtx.OptimDependOnMutableConst = true
 				break
 			}
 		} else {
@@ -533,10 +534,8 @@ func (ds *DataSource) accessPathsForConds(conditions []expression.Expression, us
 				continue
 			}
 			noIntervalRanges := ds.deriveIndexPathStats(path, conditions, true)
-			// If `AccessConds` is empty, we ignore the access path.
-			// If the path contains a full range, ignore it also. This can happen when `AccessConds` is constant true, and
-			// it comes from the result of a subquery, so it is not folded.
-			if len(path.AccessConds) == 0 || ranger.HasFullRange(path.Ranges) {
+			// If the path contains a full range, ignore it.
+			if ranger.HasFullRange(path.Ranges) {
 				continue
 			}
 			// If we have empty range, or point range on unique index, just remove other possible paths.
@@ -547,6 +546,7 @@ func (ds *DataSource) accessPathsForConds(conditions []expression.Expression, us
 					results[0] = path
 					results = results[:1]
 				}
+				ds.ctx.GetSessionVars().StmtCtx.OptimDependOnMutableConst = true
 				break
 			}
 		}