show table t next_row_id shows row id on auto_random table

[cyliu0]

Bug Report

Please answer these questions before submitting your issue. Thanks!

1. Minimal reproduce step (Required)

drop table if exists t;
create table t (a bigint primary key auto_random, b varchar(100), c varchar(100));
show table t next_row_id;

2. What did you expect to see? (Required)

+---------+------------+-------------+--------------------+----------------+
| DB_NAME | TABLE_NAME | COLUMN_NAME | NEXT_GLOBAL_ROW_ID | ID_TYPE        |
+---------+------------+-------------+--------------------+----------------+
| test    | t          | a           | 1                  | AUTO_RANDOM    |
+---------+------------+-------------+--------------------+----------------+

3. What did you see instead (Required)

+---------+------------+-------------+--------------------+----------------+
| DB_NAME | TABLE_NAME | COLUMN_NAME | NEXT_GLOBAL_ROW_ID | ID_TYPE        |
+---------+------------+-------------+--------------------+----------------+
| test    | t          | _tidb_rowid | 1                  | AUTO_INCREMENT |
| test    | t          | a           | 1                  | AUTO_RANDOM    |
+---------+------------+-------------+--------------------+----------------+

4. Affected version (Required)

mysql root@127.0.0.1:test> select tidb_version()
+-------------------------------------------------------------------+
| tidb_version()                                                    |
+-------------------------------------------------------------------+
| Release Version: v4.0.0-beta.2-691-ge0be394f0                     |
| Edition: Community                                                |
| Git Commit Hash: e0be394f0bfba8c0a1006998948d3c4c9a4ae392         |
| Git Branch: master                                                |
| UTC Build Time: 2020-06-29 02:58:38                               |
| GoVersion: go1.14.2                                               |
| Race Enabled: false                                               |
| TiKV Min Version: v3.0.0-60965b006877ca7234adaced7890d7b029ed1306 |
| Check Table Before Drop: false                                    |
+-------------------------------------------------------------------+
1 row in set
Time: 0.012s

5. Root Cause Analysis

[cyliu0]

@tangenta Check this out

[tangenta]

The fixing PR #18326 is not cherry-picked to release-4.0 because of the compatibility issue.