Re: Lossless transmission of double precision floating point

On Fri, Jul 18, 2025 at 4:12 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> "Michael J. Baars" <mjbaars1977(dot)pgsql(at)gmail(dot)com> writes:
> > I receive data from a data provider on a daily basis, and noticed how they
> > use fixed type floating point in text mode, to transmit data. As you might
> > know, this type of transmission is not lossless.
>
> It is if you use enough decimal digits. Are you sure you're not
> inventing something to worry about?

The graphs speak for themselves. They do have a problem with accuracy
in the lower digits. Transmitting doubles as byte arrays takes less
characters (especially for very small numbers) and is 100% accurate.

The current solution would be to combine the data stream and its
inverse into one, depending on the two numbers being above or below
1.0. But that is a pretty ugly client side solution.

>
> regards, tom lane