Local/Global Transaction in Cross-DC Deployment Tasklist

[JmPotato]

Development Task

Part of #18253, #20561, and tikv/pd#2759, in order to make TiDB support the Local/Global Transaction in Cross-DC Deployment, which further enables TiDB to support Cross-Region Deployment & Geo-Partition (https://github.com/pingcap/tidb/issues/18273).

• RFC: Local/Global Transaction in Cross-DC Deployment (In Chinese)
• Proposal: #20588 or Proposal: Support the Local/Global Transaction in Cross-DC Deployment

New feature

Basic Work

• [x] Update the PD Client wrapper to support the new Local/Global TSO generation. #20980 @JmPotato
• [x] Introduce the new DC location configuration. @Yisaer
• [x] Add a new Session variable tidb_txn_scope to dispatch the Local/Global Transactions. #20721 @Yisaer
• [x] Dispatch a transaction as local or global. #21353 @JmPotato

Data Constraint Check

• [x] Get the Placement Rule from DDL info. #20911 (~1 day) @Yisaer
• [x] Check the data constraint of a local transaction. #20827 (~4 days) @Yisaer
• [x] Check partition placement constraints when local transactions read data. #21426 (~4 days)
• [x] Add a middle state in altering placement policies. #21119 (~4 days) @Yisaer
• [x] Check the scheme version changing. #20809 (~3 days) @Yisaer
• [x] Check the internal SQL. #20853 (~4 days) @JmPotato
• [x] Allocate local TSO for other modules. @JmPotato #21452 (~1 day)
• [ ] Resolve the Async Commit/1PC conflicts. （ ref: https://github.com/tikv/sig-transaction/issues/63 ）

Optional Work

• [ ] Record transaction scopes in statements summary and slow logs. #20774 (~2 days)
• [ ] Provide a session variable to query the last transaction scope. #20775 （~1 day)

[Yisaer]

assign "Add a new Session variable tidb_txn_scope to dispatch the Local/Global Transactions." @Yisaer

[JmPotato]

assign "Update the PD Client wrapper to support the new Local/Global TSO generation." @JmPotato