executor: fix the missing Grantor when querying mysql.`tables_pri…

…v` (#38461)

close #38293

executor/grant.go

@@ -130,6 +130,7 @@ func (e *GrantExec) Next(ctx context.Context, req *chunk.Chunk) error {
 	// Create internal session to start internal transaction.
 	isCommit := false
 	internalSession, err := e.getSysSession()
+	internalSession.GetSessionVars().User = e.ctx.GetSessionVars().User
 	if err != nil {
 		return err
 	}

executor/grant_test.go

@@ -588,3 +588,16 @@ func TestIssue34610(t *testing.T) {
 	tk.MustExec("GRANT SELECT ON T1 to user_1@localhost;")
 	tk.MustExec("GRANT SELECT ON t1 to user_1@localhost;")
 }
+
+func TestIssue38293(t *testing.T) {
+	store := testkit.CreateMockStore(t)
+	tk := testkit.NewTestKit(t, store)
+	tk.Session().GetSessionVars().User = &auth.UserIdentity{Username: "root", Hostname: "localhost"}
+	tk.MustExec("DROP USER IF EXISTS test")
+	tk.MustExec("CREATE USER test")
+	defer func() {
+		tk.MustExec("DROP USER test")
+	}()
+	tk.MustExec("GRANT SELECT ON `mysql`.`db` TO test")
+	tk.MustQuery("SELECT `Grantor` FROM `mysql`.`tables_priv` WHERE User = 'test'").Check(testkit.Rows("root@localhost"))
+}