Re: pgsql: libpq: Grease the protocol by default

On 2026-02-23 Mo 9:08 PM, Tom Lane wrote:
> Jacob Champion<jacob(dot)champion(at)enterprisedb(dot)com> writes:
>> On Mon, Feb 23, 2026 at 4:45 PM Tom Lane<tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> Also: I was initially baffled why you thought this needs
>>> back-patching, but I guess you have one eye on packagers like
>>> Debian who think they can make older versions use newer libpq.so.
>> Right.
> Actually, that is going to be harder than you thought, because libpq
> before v18 will spit up on connection option "max_protocol_version".
> This patch will not work as-is for back-patching unless we care to
> also back-patch the addition of that option, which I'd be inclined
> to resist.
>
> Fortunately, we long ago had the foresight to invent PQlibVersion,
> so you could make addition of the extra option conditional on
> PQlibVersion(conn) >= 180000 in branches before 18.
>
>> Hmmm, looks like the -dump1.log output is actually from *before*
>> pg_upgrade actually runs:
> Yeah, I came to the same conclusion. I got a clean BF run using
> your patch together with the attached patch for the BF client.
> (In this patch, I did not worry about scenarios involving old
> minor releases. If Andrew is excited about that case he can
> extend the version-comparison logic.)
>
>

I am not worried about old minor releases. I am currently testing a
patch with similar intent to yours.

cheers

andrew

--
Andrew Dunstan
EDB:https://www.enterprisedb.com