TiDB cannot delete the old partition stats after changing one table from a partitioned table to a non-partitioned table

[Rustin170506]

Bug Report

TiDB cannot delete the old partition stats after changing one table from a partitioned table to a non-partitioned table.

1. Minimal reproduce step (Required)

1. Create partitioned table: create table ht(a int, b varchar(10), index idx_b (b)) partition by hash(a) partitions 3;
2. Insert one row into each partition: insert into ht values (1, "a"), (2, "b"), (3, "c");
3. Check the meta first: select * from mysql.stats_meta;

mysql> select * from mysql.stats_meta;
+--------------------+----------+--------------+-------+----------+
| version            | table_id | modify_count | count | snapshot |
+--------------------+----------+--------------+-------+----------+
| 445471591002800132 |      103 |            1 |     1 |        0 |
| 445471591002800141 |      104 |            1 |     1 |        0 |
| 445471591002800146 |      105 |            1 |     1 |        0 |
| 445471591002800146 |      102 |            3 |     3 |        0 |
+--------------------+----------+--------------+-------+----------+
4 rows in set (0.01 sec)

4. Remove partitions: alter table ht remove PARTITIONING;
5. Check the meta again: select * from mysql.stats_meta;

mysql> select * from mysql.stats_meta;
+--------------------+----------+--------------+-------+----------+
| version            | table_id | modify_count | count | snapshot |
+--------------------+----------+--------------+-------+----------+
| 445471591002800132 |      103 |            1 |     1 |        0 |
| 445471591002800141 |      104 |            1 |     1 |        0 |
| 445471591002800146 |      105 |            1 |     1 |        0 |
| 445471591002800146 |      107 |            3 |     3 |        0 |
+--------------------+----------+--------------+-------+----------+
4 rows in set (0.00 sec)

mysql> show stats_meta;
+---------+------------+----------------+---------------------+--------------+-----------+
| Db_name | Table_name | Partition_name | Update_time         | Modify_count | Row_count |
+---------+------------+----------------+---------------------+--------------+-----------+
| test    | ht         |                | 2023-11-07 14:41:00 |            3 |         3 |
+---------+------------+----------------+---------------------+--------------+-----------+
1 row in set (0.00 sec)

6. Wait for 5 minutes: select * from mysql.stats_meta;

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

Delete the old partition's stats.

3. What did you see instead (Required)

Nothing happened.

4. What is your TiDB version? (Required)

mysql> select tidb_version();
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| tidb_version()                                                                                                                                                                                                                                                      |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Release Version: v7.6.0-alpha-69-gbf8c728934
Edition: Community
Git Commit Hash: bf8c728934c7376765ddd943fd302fcb65af4bf0
Git Branch: master
UTC Build Time: 2023-11-01 08:29:41
GoVersion: go1.21.1
Race Enabled: false
Check Table Before Drop: false
Store: tikv |
+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)