Split from T111084.
ref_src_wiki column in flow_wiki_ref is not included in v2 index in enwiki.
``` [enwiki]> show index from flow_wiki_ref ;
+---------------+------------+---------------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------------+------------+---------------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 1 | ref_src_namespace | A | 8 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 2 | ref_src_title | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 3 | ref_type | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 4 | ref_target_namespace | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 5 | ref_target_title | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 6 | ref_src_object_type | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 7 | ref_src_object_id | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 1 | ref_src_namespace | A | 14 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 2 | ref_src_title | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 3 | ref_src_object_type | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 4 | ref_src_object_id | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 5 | ref_type | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 6 | ref_target_namespace | A | 2651 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 7 | ref_target_title | A | 2651 | NULL | NULL | | BTREE | | |
+---------------+------------+---------------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
14 rows in set (0.00 sec)
```
vs
```
[testwiki]> show index from flow_wiki_ref ;
+---------------+------------+---------------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| Table | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |
+---------------+------------+---------------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 1 | ref_src_wiki | A | 2 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 2 | ref_src_namespace | A | 26 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 3 | ref_src_title | A | 592 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 4 | ref_type | A | 592 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 5 | ref_target_namespace | A | 592 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 6 | ref_target_title | A | 592 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 7 | ref_src_object_type | A | 592 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_idx_v2 | 8 | ref_src_object_id | A | 592 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 1 | ref_src_wiki | A | 2 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 2 | ref_src_namespace | A | 19 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 3 | ref_src_title | A | 296 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 4 | ref_src_object_type | A | 296 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 5 | ref_src_object_id | A | 592 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 6 | ref_type | A | 592 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 7 | ref_target_namespace | A | 592 | NULL | NULL | | BTREE | | |
| flow_wiki_ref | 1 | flow_wiki_ref_revision_v2 | 8 | ref_target_title | A | 592 | NULL | NULL | | BTREE | | |
+---------------+------------+---------------------------+--------------+----------------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
16 rows in set (0.00 sec)
```