FYI, will try to use this API in psycopg3, which supports the PostgreSQL decimal binary format. Thank you very much: it seems exactly what needed.

Binary conversion with Python Decimal currently has disappointing performances and is slower than the text format conversion. This is likely caused by the use of Decimal.as_tuple(), which creates tuples for the return value and the digits and requires Python calls to access their values.

I have considered using libmpdec directly: personally I wouldn't be opposed to that, but the additional dependency on libmpdec-dev would earn the project no new fan :\

Ref. https://github.com/psycopg/psycopg3/issues/54