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planner: generate PointGet plans for prepare/execute statements (#42194)

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close pingcap/tidb#42125
This commit is contained in:
Yuanjia Zhang
2023-03-16 23:16:41 +08:00
committed by GitHub
parent e09a2140ca
commit 7a9388283f
4 changed files with 59 additions and 17 deletions
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10
executor/prepared_test.go
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@ -170,11 +170,10 @@ func TestIssue29850(t *testing.T) {
tkProcess = tk.Session().ShowProcess()
ps = []*util.ProcessInfo{tkProcess}
tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).Check(testkit.Rows( // cannot use PointGet since it contains a range condition
`TableReader_6 1.00 root data:TableRangeScan_5`,
`└─TableRangeScan_5 1.00 cop[tikv] table:t range:[1,1], keep order:false, stats:pseudo`))
tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).Check(testkit.Rows(
`Point_Get_5 1.00 root table:t handle:1`))
tk.MustQuery(`execute stmt using @a1, @a2`).Check(testkit.Rows("1", "2"))
tk.MustQuery(`select @@last_plan_from_cache`).Check(testkit.Rows("1"))
tk.MustQuery(`select @@last_plan_from_cache`).Check(testkit.Rows("0"))
tk.MustExec(`prepare stmt from 'select * from t where a=? or a=?'`)
tk.MustQuery(`execute stmt using @a1, @a1`).Check(testkit.Rows("1"))
@ -182,8 +181,7 @@ func TestIssue29850(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( // cannot use PointGet since it contains a or condition
`TableReader_6 1.00 root data:TableRangeScan_5`,
`└─TableRangeScan_5 1.00 cop[tikv] table:t range:[1,1], keep order:false, stats:pseudo`))
`Point_Get_5 1.00 root table:t handle:1`))
tk.MustQuery(`execute stmt using @a1, @a2`).Check(testkit.Rows("1", "2"))
}

15
planner/core/find_best_task.go
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@ -953,9 +953,6 @@ func (ds *DataSource) findBestTask(prop *property.PhysicalProperty, planCounter
canConvertPointGet := len(path.Ranges) > 0 && path.StoreType == kv.TiKV && ds.isPointGetConvertableSchema()
if canConvertPointGet && expression.MaybeOverOptimized4PlanCache(ds.ctx, path.AccessConds) {
canConvertPointGet = ds.canConvertToPointGetForPlanCache(path)
}
if canConvertPointGet && path.Index != nil && path.Index.MVIndex {
canConvertPointGet = false // cannot use PointGet upon MVIndex
}
@ -1015,6 +1012,13 @@ func (ds *DataSource) findBestTask(prop *property.PhysicalProperty, planCounter
} else {
pointGetTask = ds.convertToBatchPointGet(prop, candidate, hashPartColName, opt)
}
// Batch/PointGet plans may be over-optimized, like `a>=1(?) and a<=1(?)` --> `a=1` --> PointGet(a=1).
// For safety, prevent these plans from the plan cache here.
if !pointGetTask.invalid() && expression.MaybeOverOptimized4PlanCache(ds.ctx, candidate.path.AccessConds) && !ds.isSafePointGetPlan4PlanCache(candidate.path) {
ds.ctx.GetSessionVars().StmtCtx.SetSkipPlanCache(errors.New("Batch/PointGet plans may be over-optimized"))
}
appendCandidate(ds, pointGetTask, prop, opt)
if !pointGetTask.invalid() {
cntPlan++
@ -1094,12 +1098,11 @@ func (ds *DataSource) findBestTask(prop *property.PhysicalProperty, planCounter
return
}
func (ds *DataSource) canConvertToPointGetForPlanCache(path *util.AccessPath) bool {
func (ds *DataSource) isSafePointGetPlan4PlanCache(path *util.AccessPath) bool {
// PointGet might contain some over-optimized assumptions, like `a>=1 and a<=1` --> `a=1`, but
// these assumptions may be broken after parameters change.
// So for safety, we narrow down the scope and just generate PointGet in some particular and simple scenarios.
// scenario 1: each column corresponds to a single EQ, `a=1 and b=2 and c=3` --> `[1, 2, 3]`
// safe scenario 1: each column corresponds to a single EQ, `a=1 and b=2 and c=3` --> `[1, 2, 3]`
if len(path.Ranges) > 0 && path.Ranges[0].Width() == len(path.AccessConds) {
for _, accessCond := range path.AccessConds {
f, ok := accessCond.(*expression.ScalarFunction)

46
planner/core/plan_cache_test.go
View File

@ -1081,8 +1081,6 @@ func TestPlanCacheWithLimit(t *testing.T) {
{"prepare stmt from 'insert into t select * from t order by a desc limit ?, ?'", []int{1, 2}},
{"prepare stmt from 'update t set a = 1 limit ?'", []int{1}},
{"prepare stmt from '(select * from t order by a limit ?) union (select * from t order by a desc limit ?)'", []int{1, 2}},
{"prepare stmt from 'select * from t where a = ? limit ?, ?'", []int{1, 1, 1}},
{"prepare stmt from 'select * from t where a in (?, ?) limit ?, ?'", []int{1, 2, 1, 1}},
}
for idx, testCase := range testCases {
@ -1298,6 +1296,50 @@ func TestNonPreparedPlanCacheExplain(t *testing.T) {
}
}
func TestIssue42125(t *testing.T) {
store := testkit.CreateMockStore(t)
tk := testkit.NewTestKit(t, store)
tk.MustExec("use test")
tk.MustExec("create table t (a int, b int, c int, unique key(a, b))")
// should use BatchPointGet
tk.MustExec("prepare st from 'select * from t where a=1 and b in (?, ?)'")
tk.MustExec("set @a=1, @b=2")
tk.MustExec("execute st using @a, @b")
tkProcess := tk.Session().ShowProcess()
ps := []*util.ProcessInfo{tkProcess}
tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
rows := tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).Rows()
require.Equal(t, rows[0][0], "Batch_Point_Get_5") // use BatchPointGet
tk.MustExec("execute st using @a, @b")
tk.MustQuery("show warnings").Check(testkit.Rows("Warning 1105 skip prepared plan-cache: Batch/PointGet plans may be over-optimized"))
// should use PointGet: unsafe PointGet
tk.MustExec("prepare st from 'select * from t where a=1 and b>=? and b<=?'")
tk.MustExec("set @a=1, @b=1")
tk.MustExec("execute st using @a, @b")
tkProcess = tk.Session().ShowProcess()
ps = []*util.ProcessInfo{tkProcess}
tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
rows = tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).Rows()
require.Equal(t, rows[0][0], "Point_Get_5") // use Point_Get_5
tk.MustExec("execute st using @a, @b")
tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // cannot hit
// safe PointGet
tk.MustExec("prepare st from 'select * from t where a=1 and b=? and c<?'")
tk.MustExec("set @a=1, @b=1")
tk.MustExec("execute st using @a, @b")
tkProcess = tk.Session().ShowProcess()
ps = []*util.ProcessInfo{tkProcess}
tk.Session().SetSessionManager(&testkit.MockSessionManager{PS: ps})
rows = tk.MustQuery(fmt.Sprintf("explain for connection %d", tkProcess.ID)).Rows()
require.Contains(t, rows[0][0], "Selection") // PointGet -> Selection
require.Contains(t, rows[1][0], "Point_Get")
tk.MustExec("execute st using @a, @b")
tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1")) // can hit
}
func TestNonPreparedPlanExplainWarning(t *testing.T) {
store := testkit.CreateMockStore(t)

5
planner/core/prepare_test.go
View File

@ -1954,11 +1954,10 @@ func TestPlanCachePointGetAndTableDual(t *testing.T) {
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")
// TableReader plan would be built, we should cache it.
tk.MustQuery("execute s2 using @a2, @a2").Check(testkit.Rows())
tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
tk.MustQuery("execute s2 using @a2, @b2").Check(testkit.Rows("1 7777"))
tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0")) // PointPlan
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)")
@ -2007,7 +2006,7 @@ func TestIssue26873(t *testing.T) {
tk.MustQuery("execute stmt using @p").Check(testkit.Rows())
tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
tk.MustQuery("execute stmt using @p").Check(testkit.Rows())
tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("1"))
tk.MustQuery("select @@last_plan_from_cache").Check(testkit.Rows("0"))
}
func TestIssue29511(t *testing.T) {