In working on a Python wrapper around virtual tables, I thought it might be beneficial if SQLite provided an official C API for creating simple table-valued functions. The wrapper could build on the existing virtual table APIs and would consist of:
* user supplied list of parameters, which would be converted to HIDDEN columns in a virtual table. * user supplied list of column names, which would constitute the return values of the table-valued function * user supplied initialization function which would accept the parameters passed, i.e. SELECT * FROM user_func(p1, p2, p3), the init function would receive (p1, p2, p3). * user supplied iterate function which would accept a zero-based index and a result context, returning 1 to indicate EOF and 0 to indicate more results exist. I think this might lead to a larger ecosystem of quality open-source table-valued functions. Given the fact that creating even a simple vtable is cumbersome, providing an API that required the bare minimum seems like a good idea to me. Thoughts? PS if you're curious about the Python wrapper, I posted on it a day or two ago.
