inl_hash_join does not work as expected

[XuHuaiyu]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

tidb> use test

tidb> create table t1(a int, index(a));
Query OK, 0 rows affected (0.01 sec)

tidb> create table t2(a int, index(a));
Query OK, 0 rows affected (0.01 sec)

tidb> use test2

tidb> desc select /*+ inl_hash_join(test.t1) */ * from test.t1 join test.t2 on test.t1.a = test.t2.a;
+-----------------------------+----------+-----------+-----------------------------------------------------+
| id                          | estRows  | task      | operator info                                       |
+-----------------------------+----------+-----------+-----------------------------------------------------+
| MergeJoin_7                 | 12487.50 | root      | inner join, left key:test.t1.a, right key:test.t2.a |
| ├─IndexReader_35(Build)     | 9990.00  | root      | index:IndexFullScan_34                              |
| │ └─IndexFullScan_34        | 9990.00  | cop[tikv] | table:t2, index:a, keep order:true, stats:pseudo    |
| └─IndexReader_33(Probe)     | 9990.00  | root      | index:IndexFullScan_32                              |
|   └─IndexFullScan_32        | 9990.00  | cop[tikv] | table:t1, index:a, keep order:true, stats:pseudo    |
+-----------------------------+----------+-----------+-----------------------------------------------------+
5 rows in set, 1 warning (0.00 sec)

tidb> show warnings;
+---------+------+-------------------------------------------------------------------------------------------------------------------------------+
| Level   | Code | Message                                                                                                                       |
+---------+------+-------------------------------------------------------------------------------------------------------------------------------+
| Warning | 1815 | There are no matching table names for (t1) in optimizer hint /*+ INL_HASH_JOIN(t1) */. Maybe you can use the table alias name |
+---------+------+-------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)

2. What did you expect to see?
   indexHashJoin can be chosen forcibly

3. What version of TiDB are you using (tidb-server -V or run select tidb_version(); on TiDB)?

Release Version: v4.0.0-beta-345-gf51a7fc6e
Git Commit Hash: f51a7fc6e9b24fc0c0eb1ecb6da2e67ad8a34be4
Git Branch: master
UTC Build Time: 2020-03-12 06:26:29
GoVersion: go1.13
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false