TiDB v8.1 Documentation

• 语言: 英语
• 格式: .pdf
• 来源: download.pingcap.org

摘要

文档详细介绍了TiDB v8.1版本的更新内容，包括新功能、性能优化和bug修复。主要改进包括支持无序字符集、增强RECOVER TABLE语法、优化写性能、支持管道化特性以提升TPC-C性能等。文档还列出了与MySQL的兼容性差异，并提供了升级路径和工具优化的相关信息。

AI总结

### TiDB v8.1 Documentation Summary

#### 1. **New Features**
- **TiDB Enhancements**:
- Added case-insensitive collation support for `utf8mb4_general_ci` and `utf8_general_ci` in new clusters.
- Improved `RECOVER TABLE` syntax to support truncated table recovery.
- Enhanced performance for using sequences as default column values.
- Added the `DDLJobs` system table to query DDL job details.
- Optimized `aggFuncSum` and `EXPLAIN` output performance.
- Added support for `admin show next_row_id` and improved transaction handling with a configurable option.
- Fixed issues with `UNION ORDER BY` generating extra columns and special character escaping in `Show Create Table`.

- **TiKV Improvements**:
- Added support for the pipelined feature in pessimistic transactions, improving TPC-C performance by 20% (with a risk of commit failure due to lock issues).
- Enabled the `unify-read-pool` configuration by default in new clusters.
- Added `kv_scan` interface with an end-key limit and updated configuration options for task management.

- **PD Enhancements**:
- Added support for retrieving default PD configuration via HTTP API.
- Improved stability and performance of the placement driver under exceptional conditions.

#### 2. **Bug Fixes**
- **TiDB**:
- Fixed replication issues between upstream and downstream during DDL job execution using `PREPARE` statements.
- Resolved issues with incorrect job queries in internal records and improved `UNION` statement performance.
- Fixed DDL job rollback issues and `tidb_max_chunk_size` behavior.
- Addressed issues with `LIKE` behavior, `do_div_mod` bugs, and `UNION` statement errors.

- **TiKV**:
- Fixed issues with incomplete snapshots and iterator status checks.
- Added validation for `block-size` configuration.

- **PD**:
- Fixed issues related to `pd-ctl` reading region keys and `regions/check` API results.
- Resolved PD leader election issues and improved compact file operations in RocksDB.

#### 3. **Upgrade Information**
- **Upgrade Paths**:
- Support upgrading from TiDB 4.0, 5.0-5.4, 6.0-6.6, 7.0-7.6, and 8.0 to TiDB 8.1.
- Detailed upgrade instructions are provided for each path.

#### 4. **TiDB 2.0.8 Release Notes**
- **Improvements**:
- Slowed down auto-increment ID generation in `UPDATE` statements.
- Enhanced compatibility and stability.

- **Bug Fixes**:
- Fixed issues with time zone handling in `DateTime` default values and duplicate key updates.
- Improved etcd session recovery when the PD leader goes down.

#### 5. **TiDB 3.0.4 Release Notes**
- **New Features**:
- Added `performance_schema.events_statements_summary_by_digest` for troubleshooting.
- Introduced `WHERE` clause support in `SHOW TABLE REGIONS`.
- Added `worker-count` and `txn-batch` configuration items in Reparo for recovery speed control.

- **Improvements**:
- Enhanced batch region split performance and RocksDB double linked list performance.
- Added diagnostic tools (`iosnoop` and `funcslower`) in TiDB Ansible.
- Optimized slow query log output.

#### 6. **TiDB 2.1.13 Release Notes**
- **New Features**:
- Added support for `SHARD_ROW_ID_BITS` to scatter row IDs and reduce hotspots.
- Added `PRE_SPLIT_REGIONS` and `SPLIT TABLE` syntax for region presplitting.
- Improved DDL metadata management and added `update-stats` configuration.

- **Bug Fixes**:
- Fixed OOM issues in high-concurrency scenarios and panic issues caused by `KILL` syntax.
- Improved compatibility with MySQL for `ADD_DATE` and `IN` expression handling.

#### 7. **TiDB 1.0 Release Notes**
- **Key Features**:
- Enhanced MySQL compatibility, SQL optimization, and stability.
- Added support for `NO_SQL_CACHE`, `Stream Aggregator`, and `Batch Create Table`.

- **Improvements**:
- Optimized the Hash Aggregator operator and introduced the `Targeted Optimization for TiDB` tool.

#### 8. **Compatibility Differences**
- **Unsupported MySQL Features**:
- Stored procedures, triggers, events, user-defined functions, `FULLTEXT` syntax, GIS functions, and more.

- **Key Differences**:
- TiDB auto-increment IDs are globally unique within a single server.
- TiDB does not support XA syntax or two-phase commit via SQL.

#### 9. **Glossary**
- **ACID**: Ensures transaction atomicity, consistency, isolation, and durability. TiDB achieves atomicity through Region-level transactions and uses persistent storage for durability.
- **Bucket**: A small range within a Region used for query statistics and optimization.

This summary highlights the major updates, improvements, and compatibility considerations in TiDB v8.1, providing a concise overview of its features and enhancements.