From 458968b6e9386c88e56824c77b8801cb639a49c1 Mon Sep 17 00:00:00 2001
From: Zhi Qi <qizhi@pingcap.com>
Date: Mon, 24 May 2021 00:37:30 +0800
Subject: [PATCH] solve conflicts

---
 planner/core/exhaust_physical_plans.go | 4 ++--
 planner/core/task.go                   | 6 +++---
 sessionctx/variable/session.go         | 4 ++--
 sessionctx/variable/sysvar.go          | 5 +----
 4 files changed, 8 insertions(+), 11 deletions(-)

diff --git a/planner/core/exhaust_physical_plans.go b/planner/core/exhaust_physical_plans.go
index 5e31335ab2412..86041b54da121 100644
--- a/planner/core/exhaust_physical_plans.go
+++ b/planner/core/exhaust_physical_plans.go
@@ -2480,7 +2480,7 @@ func (p *LogicalLimit) exhaustPhysicalPlans(prop *property.PhysicalProperty) ([]
 	if !p.limitHints.preferLimitToCop {
 		allTaskTypes = append(allTaskTypes, property.RootTaskType)
 	}
-	if p.canPushToCop(kv.TiFlash) && p.ctx.GetSessionVars().AllowMPPExecution {
+	if p.canPushToCop(kv.TiFlash) && p.ctx.GetSessionVars().IsMPPAllowed() {
 		allTaskTypes = append(allTaskTypes, property.MppTaskType)
 	}
 	ret := make([]PhysicalPlan, 0, len(allTaskTypes))
@@ -2517,7 +2517,7 @@ func (p *LogicalUnionAll) exhaustPhysicalPlans(prop *property.PhysicalProperty)
 	if prop.TaskTp == property.MppTaskType && prop.PartitionTp != property.AnyType {
 		return nil, true
 	}
-	canUseMpp := p.ctx.GetSessionVars().AllowMPPExecution && p.canPushToCop(kv.TiFlash)
+	canUseMpp := p.ctx.GetSessionVars().IsMPPAllowed() && p.canPushToCop(kv.TiFlash)
 	chReqProps := make([]*property.PhysicalProperty, 0, len(p.children))
 	for range p.children {
 		if canUseMpp && prop.TaskTp == property.MppTaskType {
diff --git a/planner/core/task.go b/planner/core/task.go
index 69522c28f798c..45a0f729e41c7 100644
--- a/planner/core/task.go
+++ b/planner/core/task.go
@@ -2008,13 +2008,13 @@ func (t *mppTask) convertToRootTaskImpl(ctx sessionctx.Context) *rootTask {
 	}.Init(ctx, t.p.SelectBlockOffset())
 	p.stats = t.p.statsInfo()
 
-	p.cost = t.cst / p.ctx.GetSessionVars().CopTiFlashConcurrencyFactor
+	cst := t.cst / p.ctx.GetSessionVars().CopTiFlashConcurrencyFactor
 	if p.ctx.GetSessionVars().IsMPPEnforced() {
-		p.cost = 0
+		cst = 0
 	}
 	rt := &rootTask{
 		p:   p,
-		cst: p.cost,
+		cst: cst,
 	}
 	return rt
 }
diff --git a/sessionctx/variable/session.go b/sessionctx/variable/session.go
index 9622df335cfdc..f7f0ccd7b7566 100644
--- a/sessionctx/variable/session.go
+++ b/sessionctx/variable/session.go
@@ -500,7 +500,7 @@ type SessionVars struct {
 	AllowBatchCop int
 
 	// AllowMPPExecution means if we should use mpp way to execute query. Default value is "ON", means to be determined by the optimizer.
-	// Value set to "ENFORCE" means to use mpp whenever possible. Value set to means never use mpp.
+	// Value set to "ENFORCE" means to use mpp whenever possible. Value set to "OFF" means never use mpp.
 	allowMPPExecution string
 
 	// TiDBAllowAutoRandExplicitInsert indicates whether explicit insertion on auto_random column is allowed.
@@ -1501,7 +1501,7 @@ func (s *SessionVars) SetSystemVar(name string, val string) error {
 	case TiDBAllowBatchCop:
 		s.AllowBatchCop = int(tidbOptInt64(val, DefTiDBAllowBatchCop))
 	case TiDBAllowMPPExecution:
-		s.AllowMPPExecution = TiDBOptOn(val)
+		s.allowMPPExecution = val
 	case TiDBIndexLookupSize:
 		s.IndexLookupSize = tidbOptPositiveInt32(val, DefIndexLookupSize)
 	case TiDBHashJoinConcurrency:
diff --git a/sessionctx/variable/sysvar.go b/sessionctx/variable/sysvar.go
index 1c82a8403a403..63f378b004cc8 100644
--- a/sessionctx/variable/sysvar.go
+++ b/sessionctx/variable/sysvar.go
@@ -580,10 +580,7 @@ var defaultSysVars = []*SysVar{
 		return oracle.LocalTxnScope
 	}()},
 	/* TiDB specific variables */
-	{Scope: ScopeGlobal | ScopeSession, Name: TiDBAllowMPPExecution, Value: On, Type: TypeEnum, PossibleValues: []string{"OFF", "ON", "ENFORCE"}, SetSession: func(s *SessionVars, val string) error {
-		s.allowMPPExecution = val
-		return nil
-	}},
+	{Scope: ScopeGlobal | ScopeSession, Name: TiDBAllowMPPExecution, Value: On, Type: TypeEnum, PossibleValues: []string{"OFF", "ON", "ENFORCE"}},
 	{Scope: ScopeGlobal | ScopeSession, Name: TiDBBCJThresholdCount, Value: strconv.Itoa(DefBroadcastJoinThresholdCount), Type: TypeInt, MinValue: 0, MaxValue: math.MaxInt64},
 	{Scope: ScopeGlobal | ScopeSession, Name: TiDBBCJThresholdSize, Value: strconv.Itoa(DefBroadcastJoinThresholdSize), Type: TypeInt, MinValue: 0, MaxValue: math.MaxInt64},
 	{Scope: ScopeSession, Name: TiDBSnapshot, Value: ""},