Re: [HACKERS] Binary cursors, numerics and other types

Theo Kramer <theo(at)flame(dot)co(dot)za> writes:
> I am using the libpq interface with binary cursors and am using numeric
> fields. There seems to be no conversion routines available in the
> front end library for numeric types. Am I missing something or do
> I have to roll my own from numeric.c as per the backend?
> I also can't find anything in libpq on dates.
> Should appropriate conversion routines exist in libpq?

It is not libpq's job to try to deal with binary data from the server
--- for one thing, libpq may be compiled on a different architecture
with a different representation than the server is (wrong endianness,
different floating point format, etc). libpq doesn't even have any
way of finding out whether a conversion is needed, let alone doing it.

In the current scheme of things, binary cursors are of very limited use,
and you are *really* foolish if you try to use them for anything except
the most primitive data types like "int4". Your code will break without
warning whenever Jan feels like changing the internal representation of
numeric, as I believe he intends to do soon. We have never guaranteed
that the internal representation of date/time types is frozen, either
--- Thomas has been heard muttering about replacing timestamp with
datetime, for example.

There has been some talk of creating a CORBA interface to Postgres,
which would make use of binary representations for the basic data types
safer, since I believe CORBA offers facilities for cross-platform
transfer of binary integers (floats too? not sure). But I don't think
that would extend to nonstandard Postgres datatypes.

regards, tom lane