protocol change in 7.4

There has been some previous discussion of changing the FE/BE protocol
in 7.4, in order to fix several problems. I think this is worth doing:
if we can resolve all these issues in a single release, it will lessen
the upgrade difficulties for users.

I'm aware of the following problems that need a protocol change to fix
them:

(1) Add an optional textual message to NOTIFY

(2) Remove the hard-coded limits on database and user names
(SM_USER, SM_DATABASE), replace them with variable-length
fields.

(3) Remove some legacy elements in the startup packet
('unused' can go -- perhaps 'tty' as well). I think the
'length' field of the password packet is also not used,
but I'll need to double-check that.

(4) Fix the COPY protocol (Tom?)

(5) Fix the Fastpath protocol (Tom?)

(6) Protocol-level support for prepared queries, in order to
bypass the parser (and maybe be more compatible with the
implementation of prepared queries in other databases).

(7) Include the current transaction status, since it's
difficult for the client app to determine it for certain
(Tom/Bruce?)

If I've missed anything or if there is something you think we should
add, please let me know.

I can implement (1), (2), (3), and possibly (7), if someone can tell
me exactly what is required (my memory of the discussion relating to
this is fuzzy). The rest is up for grabs.

Finally, how should we manage the transition? I wasn't around for the
earlier protocol changes, so I'd appreciate any input on steps we can
take to improve backward-compatibility.

Cheers,

Neil

--
Neil Conway <neilc(at)samurai(dot)com> || PGP Key ID: DB3C29FC