Re-use postgres-simple ToField instance for HasSqlValueSyntax

[jmoore34]

Is there a way to reuse the postgres-simple ToField instance for implementing HasSqlValueSyntax?

[LaurentRDC]

The difference with HasSqlValueSyntax is that FromBackendRow is used to deserialize data from the database's wire protocol via the backend (e.g. via postgresql-simple), whereas HasSqlValueSyntax is used to construct queries inside beam (e.g. bypassing postgresql-simple's Query type).

If you look at postgresql-simple's ToField, you'll notice that it does not always result in a ByteString, whereas sqlite-simple's ToField is much closer to something that could be handled automatically.

Maybe there's a way to have a default instance for HasSqlValueSyntax, but I expect it would look very different than the default instance for FromBackendRow.