Robert Haas <robertmh...@gmail.com> writes: > But ... if it's just a GUC, it can be set by code on the server side > that the client knows nothing about, breaking the client. That seems > pretty bad to me.
It's impossible for the proposed patch to break *existing* clients, because they all send requested format 0 or 1, and that is exactly what they'll get back. A client that is sending -1 and assuming that it will get back a particular format could get broken if the GUC doesn't have the value it thinks, true. But I'd argue that such code is unreasonably non-robust. Can't we solve this by recommending that clients using this feature always double-check which format they actually got? ISTM that the use-cases for the feature involve checking what data type you got anyway, so that's not an unreasonable added requirement. regards, tom lane