Last year I struggled a lot trying to query a PostgreSQL database using native Julia APIs and only partially succeeded using Cxx.jl by calling C++ code that used pqxx libraries. No problem attaching to the database and getting simple strings back into Julia but I could NOT get multiple rows or mixed data type returns to unpack properly into Julia. Lots of mucking about with “unsafe_string(pointer(connection))”. Please, please make this easier!! 
I think what is needed to start with is a static (singleton) connection so that once it’s made it can be reused. Multiple DB connections are to be avoided if possible. (IMHO)