Tracking Issue for Partition Statistics

[hi-rustin]

Enhancement

In the past, there were issues with statistics information related to partition operations. Here are some examples:

1. Truncate partition does not update global statistics #39681 When we truncate a partition table, the global statistics remain unchanged.
2. TiDB can not update stats correctly after exchange a partition #47354 After we exchange a partition table, the global statistics remain unchanged.

This will impact how we generate the correct query plan. Therefore, we need to test all partition operations and fix any potential issues.

You can see more at: https://pingcap.feishu.cn/docx/VIW7d4I7KoXpx5xOsqRczZ1hnUc

Task list:

• Truncate partition does not update global statistics #39681
• TiDB can not update stats correctly after exchange a partition #47354
• TiDB can not update stats correctly after drop a partition #48182
• TiDB can not update stats correctly after reorg some partitions #48226
• Truncating the hash partition in TiDB does not automatically delete old statistics and update the global stats  #48235
• Decreasing the hash partition count in TiDB does not automatically delete old statistics and update the global stats #48233
• Increasing the hash partition count in TiDB does not automatically delete old statistics #48231
• TiDB cannot delete the old partition stats after changing one table from a partitioned table to a non-partitioned table #49547

[hi-rustin]

Test report: https://pingcap.feishu.cn/docx/XSnOdZ51IoxtjZxP3DwcOjwinoh?from=from_copylink

[hi-rustin]

Design doc: https://pingcap.feishu.cn/docx/OLCrdxHj2ojb9KxlUvUch60LnBe

[hi-rustin]

We are going to use the solution 2.

[hi-rustin]

Operation	Event	Required Info
Drop a Partition	ActionDropTablePartition	1. Global table info ✓ 2. Dropped partition info ✓
Exchange a Partition	ActionExchangeTablePartition	No event right now, but doable
Reorganize a Partition	ActionReorganizePartition	1. Global table info ✓ 2. Dropped partition info ✕ 3. Added partition info ✓
Truncate a Partition	ActionTruncateTablePartition	1. Global table info ✓ 2. Dropped partition info ✕ 3. Added partition info ✓
Increase Hash Partition Number	ActionReorganizePartition	1. Global table info ✓ 2. Dropped partition info ✕ 3. Added partition info ✓
Decrease Hash Partition Number	ActionReorganizePartition	1. Global table info ✓ 2. Dropped partition info ✕ 3. Added partition info ✓
Truncate a Hash Partition	ActionTruncateTablePartition	1. Global table info ✓ 2. Dropped partition info ✕ 3. Added partition info ✓
Remove Partitioning	ActionRemovePartitioning	1. Global table info ✓ 2. Dropped partition info ✓

[hi-rustin]

The test report after fixing: https://pingcap.feishu.cn/docx/XPYIdC4Ihoc7jNxuPficBbOgn8g