Hi Julian, Thanks for your explanation. I think we can add support for lambda expressions in CTE syntax later, for example: ``` with f as (x, y) -> x + y select f(c1, c2) from t; ```
Another thing, I provided the wrong PR link, and the correct one should be: [1] https://github.com/apache/calcite/pull/3502 Best, Hongyu On Tue, Nov 14, 2023 at 2:54 AM Julian Hyde <jhyde.apa...@gmail.com> wrote: > Thank you. I’ll take a look. > > For what it's worth, I take issue the people (not you - they are in Spark > and/or Presto) who originally describe this feature as ‘lambdas’, > ‘higher-order functions’ or ‘function values’. The lambdas can only be used > within that particular function call, not passed around as a value, and are > therefore no more lambdas than the filter ‘e -> e.sal > 10’ in the query > ’select * from emp as e where e.sal > 10’. > > The so-called ‘higher-order functions’ are all built-in, and work by > supporting a particular syntax in the parser. There is no ability to define > your own higher-order function (the equivalent of MAP, FILTER or EXISTS), > and no ability to treat the lambdas as function values that can be passed > to another function. > > The bitter irony is that SQL has always supported the MAP and FILTER > higher-order functions with a constant argument: these are the project and > filter relational operators. All the ‘lambda’ feature does is apply those > operators to nested collections, using syntax reminiscent of a real > functional programming language. > > But the good news is that, now that I have come to terms with the fact > that this feature does not really intend to make SQL into a functional > programming language, and can see that it doesn’t require vast changes to > the type system and execution model, I am happy to consider adding it to > Calcite SQL. > > Also good news: my dissatisfaction led me to create Morel, which is both a > real functional programming language and a real query language. > > Julian > > > > > On Nov 13, 2023, at 4:11 AM, Hongyu Guo <guohongyu...@gmail.com> wrote: > > > > Hi devs, > > > > I have opened a PR regarding lambda expressions, Calcite will support > > lambda expressions like `(a, b) - > a+ b` in function parameters if this > PR > > is merged. > > > > This PR includes the following: > > - Parse, validation, SqlToRel and RelToSql for lambda expressions. > > - Execution of higher-order functions for EnumerableConvention. > > - Addition of the EXISTS function to verify the correctness of the > > execution results of higher-order functions. > > > > For more details, please refer to the following links: > > [1] https://github.com/apache/calcite > > [2] https://issues.apache.org/jira/browse/CALCITE-3679 > > [3] https://issues.apache.org/jira/browse/CALCITE-6116 > > > > Best, > > Hongyu > >
