ddl: fix issue pre_split_regions table option doesn't work in the partition table. (#18144)

[ti-srebot]

cherry-pick #18144 to release-4.0

---

Signed-off-by: crazycs520 crazycs520@gmail.com

What problem does this PR solve?

Close #14478

When create partition table, the pre_split_regions table option doesn't work.

create table t (a int, b int) shard_row_id_bits = 2 pre_split_regions=2 partition by hash(a) partitions 3;

After create table, before this PR, TiDB only split 1 regino for the separate partition:

>show table t regions;
+-----------+-----------+---------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+
| REGION_ID | START_KEY | END_KEY | LEADER_ID | LEADER_STORE_ID | PEERS | SCATTERING | WRITTEN_BYTES | READ_BYTES | APPROXIMATE_SIZE(MB) | APPROXIMATE_KEYS |
+-----------+-----------+---------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+
| 44        | t_46_     | t_47_   | 45        | 1               | 45    | 0          | 0             | 0          | 0                    | 0                |
| 46        | t_47_     | t_48_   | 47        | 1               | 47    | 0          | 0             | 0          | 0                    | 0                |
| 48        | t_48_     |         | 49        | 1               | 49    | 0          | 0             | 0          | 0                    | 0                |
+-----------+-----------+---------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+

In this PR, every partition of the table will have 4 regions.

>show table t regions;
+-----------+----------------------------+----------------------------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+
| REGION_ID | START_KEY                  | END_KEY                    | LEADER_ID | LEADER_STORE_ID | PEERS | SCATTERING | WRITTEN_BYTES | READ_BYTES | APPROXIMATE_SIZE(MB) | APPROXIMATE_KEYS |
+-----------+----------------------------+----------------------------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+
| 44        | t_46_                      | t_46_r_2305843009213693952 | 45        | 1               | 45    | 0          | 0             | 0          | 0                    | 0                |
| 46        | t_46_r_2305843009213693952 | t_46_r_4611686018427387904 | 47        | 1               | 47    | 0          | 0             | 0          | 0                    | 0                |
| 48        | t_46_r_4611686018427387904 | t_46_r_6917529027641081856 | 49        | 1               | 49    | 0          | 0             | 0          | 0                    | 0                |
| 50        | t_46_r_6917529027641081856 | t_47_                      | 51        | 1               | 51    | 0          | 0             | 0          | 0                    | 0                |
| 52        | t_47_                      | t_47_r_2305843009213693952 | 53        | 1               | 53    | 0          | 0             | 0          | 0                    | 0                |
| 54        | t_47_r_2305843009213693952 | t_47_r_4611686018427387904 | 55        | 1               | 55    | 0          | 0             | 0          | 0                    | 0                |
| 56        | t_47_r_4611686018427387904 | t_47_r_6917529027641081856 | 57        | 1               | 57    | 0          | 0             | 0          | 0                    | 0                |
| 58        | t_47_r_6917529027641081856 | t_48_                      | 59        | 1               | 59    | 0          | 0             | 0          | 0                    | 0                |
| 60        | t_48_                      | t_48_r_2305843009213693952 | 61        | 1               | 61    | 0          | 0             | 0          | 0                    | 0                |
| 62        | t_48_r_2305843009213693952 | t_48_r_4611686018427387904 | 63        | 1               | 63    | 0          | 0             | 0          | 0                    | 0                |
| 64        | t_48_r_4611686018427387904 | t_48_r_6917529027641081856 | 65        | 1               | 65    | 0          | 0             | 0          | 0                    | 0                |
| 66        | t_48_r_6917529027641081856 |                            | 67        | 1               | 67    | 0          | 0             | 0          | 0                    | 0                |
+-----------+----------------------------+----------------------------+-----------+-----------------+-------+------------+---------------+------------+----------------------+------------------+kk

What is changed and how it works?

Related changes

• Need to cherry-pick to the release branch

Check List

Tests

• Unit test

Side effects

• No

Release note

• Fix issue pre_split_regions table option doesn't work in the partition table.

[ti-srebot]

/run-all-tests

[wjhuang2016]

LGTM

[AilinKid]

LGTM

[crazycs520]

/run-all-tests

[crazycs520]

/run-integration-copr-test

[crazycs520]

/run-unit-test