>> It only checks for server version 8 or newer as I couldn't easily
find
>> the threshold for the RETURNING support.
>
> 8.1.5 does not have it. I suppose it is 8.2 feature. You can check by
> looking into 8.1 and 8.2 documentation, and, I suppose, "what's new"
> for 8.2
Yes, it is new in 8.2.
Yours,
Laurenz Albe