This is an automated cherry-pick of pingcap#61608

Signed-off-by: ti-chi-bot <[email protected]>

Author: hawkingrei

pkg/planner/core/plan_cost_ver1.go

@@ -29,6 +29,7 @@ import (
 	"github.com/pingcap/tidb/pkg/planner/util/optimizetrace"
 	"github.com/pingcap/tidb/pkg/sessionctx/variable"
 	"github.com/pingcap/tidb/pkg/statistics"
+	"github.com/pingcap/tidb/pkg/util/intest"
 	"github.com/pingcap/tidb/pkg/util/paging"
 )
 
@@ -87,6 +88,7 @@ func (p *PhysicalProjection) GetCost(count float64) float64 {
 
 // GetPlanCostVer1 calculates the cost of the plan if it has not been calculated yet and returns the cost.
 func (p *PhysicalProjection) GetPlanCostVer1(taskType property.TaskType, option *optimizetrace.PlanCostOption) (float64, error) {
+	intest.Assert(p.SCtx().GetSessionVars().CostModelVersion != 0)
 	costFlag := option.CostFlag
 	if p.PlanCostInit && !hasCostFlag(costFlag, costusage.CostFlagRecalculate) {
 		return p.PlanCost, nil

pkg/sessionctx/variable/session.go

@@ -2226,6 +2226,7 @@ func NewSessionVars(hctx HookContext) *SessionVars {
 		EnableRedactLog:               DefTiDBRedactLog,
 		EnableWindowFunction:          DefEnableWindowFunction,
 		OptOrderingIdxSelRatio:        DefTiDBOptOrderingIdxSelRatio,
+		CostModelVersion:              DefTiDBCostModelVer,
 	}
 	vars.status.Store(uint32(mysql.ServerStatusAutocommit))
 	vars.StmtCtx.ResourceGroupName = resourcegroup.DefaultResourceGroupName

pkg/util/mock/context.go

@@ -668,9 +668,14 @@ func newContext() *Context {
 	vars.StmtCtx.MemTracker.AttachTo(vars.MemTracker)
 	vars.StmtCtx.DiskTracker.AttachTo(vars.DiskTracker)
 	vars.GlobalVarsAccessor = variable.NewMockGlobalAccessor()
+<<<<<<< HEAD
 	vars.EnablePaging = variable.DefTiDBEnablePaging
 	vars.MinPagingSize = variable.DefMinPagingSize
 	vars.CostModelVersion = variable.DefTiDBCostModelVer
+=======
+	vars.EnablePaging = vardef.DefTiDBEnablePaging
+	vars.MinPagingSize = vardef.DefMinPagingSize
+>>>>>>> 1ef4c269cd7 (planner: set the default of the tidb_cost_model_version correctly (#61608))
 	vars.EnableChunkRPC = true
 	vars.DivPrecisionIncrement = variable.DefDivPrecisionIncrement
 	if err := sctx.GetSessionVars().SetSystemVar(variable.MaxAllowedPacket, "67108864"); err != nil {