Hi, ZheHu Thanks for your reply, makes sense to me.
Best, Ron Zhe Hu <iluff...@163.com> 于2025年2月8日周六 20:35写道： > As far as I can tell, RelToSqlConverter is a suitable way to unparse a > RelNode, which is also how our team applied it currently. > For your question 1, the output SQL after rel2sql may not be exactly the > same as your original query when using some optimized rules, however, more > efficient (at least this is one of the goals). And I think you can find > some useful information here: https://calcite.apache.org/docs/algebra.html. > Since we can set dialect for rel2sql, there may also be a little semantic > difference, which provides you an option to query different data sources. > For your question 2, if a RelNode cannot be converted to SQL text, I think > it’s possibly a bug. > > > I hope those information can be helpful for you. > > > Best > ZheHu > > > > > ---- Replied Message ---- > | From | Ron Liu<ron9....@gmail.com> | > | Date | 02/8/2025 15:50 | > | To | <dev@calcite.apache.org> | > | Subject | [Discuss] Converting RelNode/RexNode to SQL Text | > Hello, Dev! > > I am a contributor to Apache Flink. As you know, Flink SQL uses Apache > Calcite as a framework for SQL parsing and optimization. For a SQL, Calcite > will go through the transformation of SQL Text -> SqlNode -> RelNode. Now I > have a requirement to reverse parse RelNode to SQL Text. By digging into > the Calcite code, I found a tool RelToSqlConverter that can convert RelNode > to SQL Text. Since Calcite may generate some unreadable intermediate > variables during the process of converting SQL text to RelNode, I have the > following concern when using RelToSqlConverter to reverse parse RelNode to > SQL: > 1. Can the SQL text parsed by RelToSqlConverter be equal to the original > input SQL text? > 2. Does RelToSqlConverter support parsing all RelNodes to SQL text? > > To summarize, my key question is whether using RelToSqlConverter to unparse > a RelNode into SQL text is a production-ready solution? Since I don't know > much about Calcite, I came to the community to ask for help. > > Other input: I found that the Coral[1] project is using RelToSqlConverter > to unparsing RelNode into SQL text, which looks like a viable solution. > > 1. https://github.com/linkedin/coral > > Best, > Ron >
