diff --git a/expression/expr_to_pb_test.go b/expression/expr_to_pb_test.go
index 610beede45..cf949394e7 100644
--- a/expression/expr_to_pb_test.go
+++ b/expression/expr_to_pb_test.go
@@ -1246,11 +1246,6 @@ func TestExprPushDownToTiKV(t *testing.T) {
 			retType:      types.NewFieldType(mysql.TypeString),
 			args:         []Expression{stringColumn, intColumn},
 		},
-		{
-			functionName: ast.Left,
-			retType:      types.NewFieldType(mysql.TypeString),
-			args:         []Expression{stringColumn, intColumn},
-		},
 		{
 			functionName: ast.Sin,
 			retType:      types.NewFieldType(mysql.TypeDouble),
diff --git a/expression/expression.go b/expression/expression.go
index d611f1a8c8..fe56ff5520 100644
--- a/expression/expression.go
+++ b/expression/expression.go
@@ -975,7 +975,7 @@ func scalarExprSupportedByTiKV(sf *ScalarFunction) bool {
 		ast.Length, ast.BitLength, ast.Concat, ast.ConcatWS, ast.Replace, ast.ASCII, ast.Hex,
 		ast.Reverse, ast.LTrim, ast.RTrim, ast.Strcmp, ast.Space, ast.Elt, ast.Field,
 		InternalFuncFromBinary, InternalFuncToBinary, ast.Mid, ast.Substring, ast.Substr, ast.CharLength,
-		ast.Right, ast.Left,
+		ast.Right, /* ast.Left */
 
 		// json functions.
 		ast.JSONType, ast.JSONExtract, ast.JSONObject, ast.JSONArray, ast.JSONMerge, ast.JSONSet,
diff --git a/planner/core/integration_test.go b/planner/core/integration_test.go
index 75f3c65186..e87e689d67 100644
--- a/planner/core/integration_test.go
+++ b/planner/core/integration_test.go
@@ -2771,10 +2771,6 @@ func TestScalarFunctionPushDown(t *testing.T) {
 	tk.MustQuery("explain analyze select /*+read_from_storage(tikv[t])*/ * from t where right(c,1);").
 		CheckAt([]int{0, 3, 6}, rows)
 
-	rows[1][2] = "left(test.t.c, 1)"
-	tk.MustQuery("explain analyze select /*+read_from_storage(tikv[t])*/ * from t where left(c,1);").
-		CheckAt([]int{0, 3, 6}, rows)
-
 	rows[1][2] = "mod(test.t.id, test.t.id)"
 	tk.MustQuery("explain analyze select /*+read_from_storage(tikv[t])*/ * from t where mod(id, id);").
 		CheckAt([]int{0, 3, 6}, rows)
diff --git a/planner/core/testdata/integration_suite_out.json b/planner/core/testdata/integration_suite_out.json
index 242bac6254..0024560973 100644
--- a/planner/core/testdata/integration_suite_out.json
+++ b/planner/core/testdata/integration_suite_out.json
@@ -2077,11 +2077,11 @@
         "SQL": "select /*+ use_index_merge(t1) */ 1 from t1 where c1 = 'ab' or c2 = '10' and char_length(left(c1, 10)) = 10;",
         "Plan": [
           "Projection 17.99 root  1->Column#5",
-          "└─IndexMerge 0.04 root  ",
-          "  ├─IndexRangeScan(Build) 10.00 cop[tikv] table:t1, index:c1(c1) range:[\"ab\",\"ab\"], keep order:false, stats:pseudo",
-          "  ├─IndexRangeScan(Build) 10.00 cop[tikv] table:t1, index:c2(c2) range:[\"10\",\"10\"], keep order:false, stats:pseudo",
-          "  └─Selection(Probe) 0.04 cop[tikv]  or(eq(test.t1.c1, \"ab\"), and(eq(test.t1.c2, \"10\"), eq(char_length(left(test.t1.c1, 10)), 10)))",
-          "    └─TableRowIDScan 19.99 cop[tikv] table:t1 keep order:false, stats:pseudo"
+          "└─Selection 0.04 root  or(eq(test.t1.c1, \"ab\"), and(eq(test.t1.c2, \"10\"), eq(char_length(left(test.t1.c1, 10)), 10)))",
+          "  └─IndexMerge 19.99 root  ",
+          "    ├─IndexRangeScan(Build) 10.00 cop[tikv] table:t1, index:c1(c1) range:[\"ab\",\"ab\"], keep order:false, stats:pseudo",
+          "    ├─IndexRangeScan(Build) 10.00 cop[tikv] table:t1, index:c2(c2) range:[\"10\",\"10\"], keep order:false, stats:pseudo",
+          "    └─TableRowIDScan(Probe) 19.99 cop[tikv] table:t1 keep order:false, stats:pseudo"
         ],
         "Res": [
           "1"
@@ -2105,12 +2105,11 @@
         "SQL": "select /*+ use_index_merge( tt2 ) */ 1 from tt2 where tt2.c1 in (-3896405) or tt2.pk in (1, 53330) and to_base64(left(pk, 5));",
         "Plan": [
           "Projection 2.60 root  1->Column#3",
-          "└─IndexMerge 0.00 root  ",
-          "  ├─IndexRangeScan(Build) 1.00 cop[tikv] table:tt2, index:c1(c1) range:[-3896405,-3896405], keep order:false, stats:pseudo",
-          "  ├─Selection(Build) 1.60 cop[tikv]  istrue_with_null(cast(to_base64(left(cast(test.tt2.pk, var_string(20)), 5)), double BINARY))",
-          "  │ └─TableRangeScan 2.00 cop[tikv] table:tt2 range:[1,1], [53330,53330], keep order:false, stats:pseudo",
-          "  └─Selection(Probe) 0.00 cop[tikv]  or(eq(test.tt2.c1, -3896405), and(in(test.tt2.pk, 1, 53330), istrue_with_null(cast(to_base64(left(cast(test.tt2.pk, var_string(20)), 5)), double BINARY))))",
-          "    └─TableRowIDScan 3.00 cop[tikv] table:tt2 keep order:false, stats:pseudo"
+          "└─Selection 0.00 root  or(eq(test.tt2.c1, -3896405), and(in(test.tt2.pk, 1, 53330), istrue_with_null(cast(to_base64(left(cast(test.tt2.pk, var_string(20)), 5)), double BINARY))))",
+          "  └─IndexMerge 3.00 root  ",
+          "    ├─IndexRangeScan(Build) 1.00 cop[tikv] table:tt2, index:c1(c1) range:[-3896405,-3896405], keep order:false, stats:pseudo",
+          "    ├─TableRangeScan(Build) 2.00 cop[tikv] table:tt2 range:[1,1], [53330,53330], keep order:false, stats:pseudo",
+          "    └─TableRowIDScan(Probe) 3.00 cop[tikv] table:tt2 keep order:false, stats:pseudo"
         ],
         "Res": [
           "1"