SQL is simply converted into a logical relation algebra tree. So anything that can do that could be used. It's a shame that PSQL doesn't provide an API for this

SQL is simply converted into a logical relation algebra tree. So anything that can do that could be used. It's a shame that PSQL doesn't provide an API for this, then all the quirks of SQL could be fixed. However, then we would probably have a proliferation of non-standard SQL like what happened with JavaScript, and standard tooling couldn't be used. SQL is somewhat nice because its fairly well standardized.