\echo :VERSION PostgreSQL 10devel on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609, 64-bit
Probably some :VERSION_NUM would make some sense. See attached PoC patch. Would it make sense?
Maybe better name for you CLIENT_VERSION_NUM
If it was starting from nothing I would tend to agree with you, but there is already an existing :VERSION variable, so it seemed logical to keep on and create variants with the same prefix.
you have true - so VERSION_NUM should be client side version
Can be SERVER_VERSION_NUM taken from connection info?
Probably it could. It seems a little less straightforward than defining a client-side string at compile time. The information is displayed when the connection is established, so the information is there somewhere.
I'm anxious to help with these patches, but they seem a bit of a moving target. Happy to jump in and review as soon as we've settled on what should be done.