'Delete' object has no attribute 'values' about databases

[tomchristie]

It'd be nice if the package could interpret the query passed in, and translate it.

I'm not sure exactly what you mean "interpret the query passed in, and translate it."

Happy to accept a pull request with a failing test for this and the proposed fix.

[szelenka]

I did some more digging, and it seems the problem is with using SQLAlchemy's bindparam in a statement and passing the values to the values param. I get similar errors with using sa.select with a bindparam in it.

_build_query is what throws the exception, but I couldn't find where a ClauseElement has a method "values" on it.

I tried converting the query to a str then wrapping it in text to assign the bindparams

    @staticmethod
    def _build_query(
        query: typing.Union[ClauseElement, str], values: dict = None
    ) -> ClauseElement:
        if isinstance(query, str):
            query = text(query)

            return query.bindparams(**values) if values is not None else query
        elif values:
            try:
                return query.values(**values)
            except AttributeError as ex:
                return text(str(query)).bindparams(**values)

        return query

However, this introduced a different problem inside _compile method when attempting to use the fetch_one/fetch_all methods, where the compiled._result_columns would contain an empty list:
https://github.com/encode/databases/blob/master/databases/backends/postgres.py#L179

The data is still returned correctly, and you can access them via named keys, but the shorthand for dict() conversion of the returned asyncpg.Record object fails due to compiled._result_columns being empty when this package attempts to create an instance of it here (where it passes in an empty result_columns):
https://github.com/encode/databases/blob/master/databases/backends/postgres.py#L144

A workaround is to simply not use bindparam and let SQLAlchemy handle all the compiling without passing values into the execute/fetch methods of this package.

I'll keep poking around to see if I can find a better solution, but may just end up stop using bindparams in my statements.

[tomchristie]

I think we've several issues with .bindparam - https://github.com/encode/databases/search?q=bindparam&type=Issues (Specifically #79, #103)

Is there an easy way to detect if bindparam has been used? Perhaps we ought to just raise a hard error in that case, and treat any bindparam usage as currently being out of scope?