diff --git a/optimizer/optimizer.go b/optimizer/optimizer.go
index ca8794cb75..655cf2496f 100644
--- a/optimizer/optimizer.go
+++ b/optimizer/optimizer.go
@@ -39,18 +39,16 @@ func Optimize(ctx context.Context, node ast.Node) (plan.Plan, error) {
 	if err != nil {
 		return nil, errors.Trace(err)
 	}
-	err = plan.Refine(p)
-	if err != nil {
-		return nil, errors.Trace(err)
-	}
-
-	bestPlan := p
-	bestCost := plan.EstimateCost(p)
-
 	alts, err := plan.Alternatives(p)
 	if err != nil {
 		return nil, errors.Trace(err)
 	}
+	err = plan.Refine(p)
+	if err != nil {
+		return nil, errors.Trace(err)
+	}
+	bestCost := plan.EstimateCost(p)
+	bestPlan := p
 	for _, alt := range alts {
 		err = plan.Refine(alt)
 		if err != nil {