计划移除 Hint DistSQL

RaigorJiang · 2023 年2 月 3 日 06:32

大家好，Hint DistSQL 已经存在很长时间了，但在使用上一直有些不方便，例如：

需要用户发送多次 SQL 语句
需要额外的 CLEAR 语句来清理 Hint value
需要对 Proxy 线程进行特殊处理（带来性能问题）

现在 SQL Hint 已经非常好用，我提议删除 Hint DistSQL，大家可以关注如下 issue：

github.com/apache/shardingsphere

Remove Hint DistSQL

opened 05:32AM - 03 Feb 23 UTC

RaigorJiang

in: proxy in: API feature: DistSQL

Hi community, Since [SQL Hint](https://shardingsphere.apache.org/document/cur…rent/en/user-manual/shardingsphere-jdbc/special-api/sharding/hint/#use-special-sql-comments) is more convenient and compatible with Proxy, I think it is time to consider removing [Hint DistSQL](https://shardingsphere.apache.org/document/current/en/user-manual/shardingsphere-proxy/distsql/syntax/ral/hint/). #### Using DistSQL to implement Hint has the following problems: 1. To execute a query, the user needs to send `Hint DistSQL` and `DML SQL` separately, which is not friendly to use; 2. After using `Hint DistSQL`, the user needs to send an additional `CLEAR` statement; 3. When Hint is enabled, Proxy needs to make a special judgment on the connected thread, which increases the complexity; ([link](https://github.com/apache/shardingsphere/blob/efe9ee21266d6507dee4639eb0c19a6d98992325/proxy/frontend/core/src/main/java/org/apache/shardingsphere/proxy/frontend/state/impl/OKProxyState.java#L61)) Now, SQL Hint can perfectly solve the above problems, so I suggest to start the work of removing Hint DistSQL, with the following tasks: - [ ] Remove `HintRALStatementExecutor` and implementation - [ ] Remove `HintRALBackendHandler` - [ ] Remove `HintRALStatement` and subclasses - [ ] Remove Hint DistSQL documentation - [ ] Remove the judgment related to Hint in `OKProxyState` - [ ] Remove the configuration item: `proxy-hint-enabled` - [ ] Remove related test cases