fixup

planner/core/plan_cost_test.go

@@ -16,6 +16,7 @@ package core_test
 
 import (
 	"fmt"
+	"strconv"
 	"strings"
 	"testing"
 
@@ -967,3 +968,39 @@ func TestTrueCardCost(t *testing.T) {
 	checkPlanCost(`select * from t where a>10 limit 10`)
 	checkPlanCost(`select sum(a), b*2 from t use index(b) group by b order by sum(a) limit 10`)
 }
+
+func TestIssue36243(t *testing.T) {
+	store, clean := testkit.CreateMockStore(t)
+	defer clean()
+	tk := testkit.NewTestKit(t, store)
+
+	tk.MustExec("use test")
+	tk.MustExec(`create table t (a int)`)
+	tk.MustExec(`insert into mysql.expr_pushdown_blacklist values ('>','tikv','')`)
+	tk.MustExec(`admin reload expr_pushdown_blacklist`)
+	tk.MustExec(`set @@tidb_enable_new_cost_interface=1`)
+
+	getCost := func() (selCost, readerCost float64) {
+		res := tk.MustQuery(`explain format=verbose select * from t where a>0`).Rows()
+		// TableScan -> TableReader -> Selection
+		require.Equal(t, len(res), 3)
+		require.Contains(t, res[0][0], "Selection")
+		require.Contains(t, res[1][0], "TableReader")
+		require.Contains(t, res[2][0], "Scan")
+		var err error
+		selCost, err = strconv.ParseFloat(res[0][2].(string), 64)
+		require.NoError(t, err)
+		readerCost, err = strconv.ParseFloat(res[1][2].(string), 64)
+		require.NoError(t, err)
+		return
+	}
+
+	tk.MustExec(`set @@tidb_cost_model_version=1`)
+	// Selection has the same cost with TableReader, ignore Selection cost for compatibility in cost model ver1.
+	selCost, readerCost := getCost()
+	require.Equal(t, selCost, readerCost)
+
+	tk.MustExec(`set @@tidb_cost_model_version=2`)
+	selCost, readerCost = getCost()
+	require.True(t, selCost > readerCost)
+}