missing build and probe suffix for index merge operator

[zz-jason]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. What did you do?

enable index merge, check the execution plan:

TiDB(root@127.0.0.1:test) > create table t (a bigint, b bigint, index idx_a(a), index idx_b(b));
Query OK, 0 rows affected (0.01 sec)

TiDB(root@127.0.0.1:test) > set @@tidb_enable_index_merge = 1;
Query OK, 0 rows affected (0.00 sec)

TiDB(root@127.0.0.1:test) > desc select * from t use index(idx_a, idx_b) where a > 1 or b > 1;
+-------------------------+---------+-----------+------------------------------------------------------------------+
| id                      | estRows | task      | operator info                                                    |
+-------------------------+---------+-----------+------------------------------------------------------------------+
| IndexMerge_16           | 6666.67 | root      |                                                                  |
| ├─IndexRangeScan_13     | 3333.33 | cop[tikv] | table:t, index:a, range:(1,+inf], keep order:false, stats:pseudo |
| ├─IndexRangeScan_14     | 3333.33 | cop[tikv] | table:t, index:b, range:(1,+inf], keep order:false, stats:pseudo |
| └─TableRowIDScan_15     | 6666.67 | cop[tikv] | table:t, keep order:false, stats:pseudo                          |
+-------------------------+---------+-----------+------------------------------------------------------------------+
4 rows in set (0.00 sec)

2. What did you expect to see?

show the build and probe side as index lookup did:

TiDB(root@127.0.0.1:test) > desc select * from t use index(idx_a) where a > 1 or b > 1;
+------------------------------+----------+-----------+--------------------------------------------------+
| id                           | estRows  | task      | operator info                                    |
+------------------------------+----------+-----------+--------------------------------------------------+
| IndexLookUp_8                | 8000.00  | root      |                                                  |
| ├─IndexFullScan_5(Build)     | 10000.00 | cop[tikv] | table:t, index:a, keep order:false, stats:pseudo |
| └─Selection_7(Probe)         | 8000.00  | cop[tikv] | or(gt(test.t.a, 1), gt(test.t.b, 1))             |
|   └─TableRowIDScan_6         | 10000.00 | cop[tikv] | table:t, keep order:false, stats:pseudo          |
+------------------------------+----------+-----------+--------------------------------------------------+
4 rows in set (0.00 sec)

3. What did you see instead?

didn't show these two suffixes.

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

TiDB(root@127.0.0.1:test) > select tidb_version()\G
*************************** 1. row ***************************
tidb_version(): Release Version: v4.0.0-beta-329-g0aef6eca2
Git Commit Hash: 0aef6eca2c661a69819f403be20a743a978cbe70
Git Branch: master
UTC Build Time: 2020-03-08 04:56:50
GoVersion: go1.13.8
Race Enabled: false
TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306
Check Table Before Drop: false
1 row in set (0.01 sec)

[LittleFall]

Is this your expectation?

+--------------------------------+---------+-----------+------------------------------------------------------------------+
| id                             | estRows | task      | operator info                                                    |
+--------------------------------+---------+-----------+------------------------------------------------------------------+
| IndexMerge_16                  | 6666.67 | root      |                                                                  |
| ├─IndexRangeScan_13 (Build)    | 3333.33 | cop[tikv] | table:t, index:a, range:(1,+inf], keep order:false, stats:pseudo |
| ├─IndexRangeScan_14 (Build)    | 3333.33 | cop[tikv] | table:t, index:b, range:(1,+inf], keep order:false, stats:pseudo |
| └─TableRowIDScan_15 (Probe)    | 6666.67 | cop[tikv] | table:t, keep order:false, stats:pseudo                          |
+--------------------------------+---------+-----------+------------------------------------------------------------------+