Note about upcoming instability in FE/BE protocol

I am about to start committing changes to CVS tip to implement the
planned FE/BE protocol changes.  My plan is to do this a bit at a time,
since I don't want to get far out of sync with CVS.  This means that the
actual protocol supported by CVS tip is going to change little by
little.  Yesterday's libpq may or may not talk to today's server.

To try to keep people from wasting time chasing version-skew problems
while this goes on, I have devised the following plan.  The server and
libpq will claim to speak protocol numbers 3.100, 3.101, 3.102, etc,
changing each time a visible change is committed.  There is also a
temporary hack in postmaster.c that will reject connections from clients
claiming to speak 3.anything-other-than-postmaster's-version.  If you
have an out-of-sync libpq, you will get something like
FATAL: unsupported frontend protocol 3.110: server supports 1.0 to 3.109
or
FATAL: Your development libpq is out of sync with the server

After the dust settles, I'll reset the protocol version number to 3.0
for release.

Note that this should only affect libpq.  Other clients may continue to
speak protocol 2.0 while this is going on, and that should not change.
In emergency you should be able to use a 7.3 copy of libpq.so to talk to
the CVS-tip server.
        regards, tom lane