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planner: fix incorrect cost when the plan has IndexLookup->Limit (#…
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…44041) (#44087)

close #44025
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@ti-chi-bot
ti-chi-bot authored May 23, 2023
1 parent 504bcdf commit b3da118
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Showing 3 changed files with 57 additions and 14 deletions.
31 changes: 31 additions & 0 deletions planner/core/find_best_task.go
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Original file line number Diff line number Diff line change
Expand Up @@ -321,7 +321,38 @@ func getTaskPlanCost(t task, op *physicalOptimizeOp) (float64, bool, error) {
case *rootTask:
taskType = property.RootTaskType
case *copTask: // no need to know whether the task is single-read or double-read, so both CopSingleReadTaskType and CopDoubleReadTaskType are OK
cop := t.(*copTask)
if cop.indexPlan != nil && cop.tablePlan != nil { // handle IndexLookup specially
taskType = property.CopMultiReadTaskType
// keep compatible with the old cost interface, for CopMultiReadTask, the cost is idxCost + tblCost.
if !cop.indexPlanFinished { // only consider index cost in this case
idxCost, err := getPlanCost(cop.indexPlan, taskType, NewDefaultPlanCostOption().WithOptimizeTracer(op))
return idxCost, false, err
}
// consider both sides
idxCost, err := getPlanCost(cop.indexPlan, taskType, NewDefaultPlanCostOption().WithOptimizeTracer(op))
if err != nil {
return 0, false, err
}
tblCost, err := getPlanCost(cop.tablePlan, taskType, NewDefaultPlanCostOption().WithOptimizeTracer(op))
if err != nil {
return 0, false, err
}
return idxCost + tblCost, false, nil
}

taskType = property.CopSingleReadTaskType

// TiFlash can run cop task as well, check whether this cop task will run on TiKV or TiFlash.
if cop.tablePlan != nil {
leafNode := cop.tablePlan
for len(leafNode.Children()) > 0 {
leafNode = leafNode.Children()[0]
}
if tblScan, isScan := leafNode.(*PhysicalTableScan); isScan && tblScan.StoreType == kv.TiFlash {
taskType = property.MppTaskType
}
}
case *mppTask:
taskType = property.MppTaskType
default:
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9 changes: 9 additions & 0 deletions planner/core/plan_cost_ver2_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -280,6 +280,15 @@ func TestIndexJoinPenaltyCost(t *testing.T) {
require.Greater(t, cost3, cost2)
}

func TestIssue44025(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, d int, index ia(a), index ibc(b,c))`)
tk.MustExec(`set @@tidb_cost_model_version=1`)
tk.MustUseIndex(`select * from t where a between 1 and 5 and b != 200 and c = 20 limit 100000`, `ia(a)`)
}

func BenchmarkGetPlanCost(b *testing.B) {
store := testkit.CreateMockStore(b)
tk := testkit.NewTestKit(b, store)
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31 changes: 17 additions & 14 deletions planner/core/testdata/enforce_mpp_suite_out.json
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Original file line number Diff line number Diff line change
Expand Up @@ -51,10 +51,11 @@
{
"SQL": "explain format='verbose' select /*+ read_from_storage(tiflash[t]) */ count(*) from t where a=1",
"Plan": [
"StreamAgg_10 1.00 64007.91 root funcs:count(1)->Column#4",
"└─TableReader_24 10.00 63508.91 root data:Selection_23",
" └─Selection_23 10.00 952000.00 cop[tiflash] eq(test.t.a, 1)",
" └─TableFullScan_22 10000.00 928000.00 cop[tiflash] table:t keep order:false, stats:pseudo"
"StreamAgg_20 1.00 63520.28 root funcs:count(Column#6)->Column#4",
"└─TableReader_21 1.00 63470.38 root data:StreamAgg_9",
" └─StreamAgg_9 1.00 952024.00 batchCop[tiflash] funcs:count(1)->Column#6",
" └─Selection_19 10.00 952000.00 batchCop[tiflash] eq(test.t.a, 1)",
" └─TableFullScan_18 10000.00 928000.00 batchCop[tiflash] table:t keep order:false, stats:pseudo"
],
"Warn": null
},
Expand Down Expand Up @@ -91,10 +92,11 @@
{
"SQL": "explain format='verbose' select /*+ read_from_storage(tiflash[t]) */ count(*) from t where a=1",
"Plan": [
"StreamAgg_12 1.00 64007.91 root funcs:count(1)->Column#4",
"└─TableReader_31 10.00 63508.91 root data:Selection_30",
" └─Selection_30 10.00 952000.00 cop[tiflash] eq(test.t.a, 1)",
" └─TableFullScan_29 10000.00 928000.00 cop[tiflash] table:t keep order:false, stats:pseudo"
"StreamAgg_27 1.00 63520.28 root funcs:count(Column#7)->Column#4",
"└─TableReader_28 1.00 63470.38 root data:StreamAgg_11",
" └─StreamAgg_11 1.00 952024.00 batchCop[tiflash] funcs:count(1)->Column#7",
" └─Selection_26 10.00 952000.00 batchCop[tiflash] eq(test.t.a, 1)",
" └─TableFullScan_25 10000.00 928000.00 batchCop[tiflash] table:t keep order:false, stats:pseudo"
],
"Warn": null
},
Expand Down Expand Up @@ -126,10 +128,11 @@
{
"SQL": "explain format='verbose' select /*+ read_from_storage(tiflash[t]) */ count(*) from t where a=1",
"Plan": [
"StreamAgg_12 1.00 64007.91 root funcs:count(1)->Column#4",
"└─TableReader_31 10.00 63508.91 root data:Selection_30",
" └─Selection_30 10.00 952000.00 cop[tiflash] eq(test.t.a, 1)",
" └─TableFullScan_29 10000.00 928000.00 cop[tiflash] table:t keep order:false, stats:pseudo"
"StreamAgg_27 1.00 63520.28 root funcs:count(Column#7)->Column#4",
"└─TableReader_28 1.00 63470.38 root data:StreamAgg_11",
" └─StreamAgg_11 1.00 952024.00 batchCop[tiflash] funcs:count(1)->Column#7",
" └─Selection_26 10.00 952000.00 batchCop[tiflash] eq(test.t.a, 1)",
" └─TableFullScan_25 10000.00 928000.00 batchCop[tiflash] table:t keep order:false, stats:pseudo"
],
"Warn": null
},
Expand Down Expand Up @@ -165,8 +168,8 @@
"Plan": [
"StreamAgg_27 1.00 49.90 root funcs:count(Column#7)->Column#4",
"└─TableReader_28 1.00 0.00 root data:StreamAgg_11",
" └─StreamAgg_11 1.00 1427024.00 batchCop[tiflash] funcs:count(1)->Column#7",
" └─Selection_26 10.00 1427000.00 batchCop[tiflash] eq(test.t.a, 1)",
" └─StreamAgg_11 1.00 952024.00 batchCop[tiflash] funcs:count(1)->Column#7",
" └─Selection_26 10.00 952000.00 batchCop[tiflash] eq(test.t.a, 1)",
" └─TableFullScan_25 10000.00 928000.00 batchCop[tiflash] table:t keep order:false, stats:pseudo"
],
"Warn": null
Expand Down

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