Re: Protocol forced to V2 in low-memory conditions?

On Tue, Sep 10, 2013 at 9:53 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Andres Freund <andres(at)2ndquadrant(dot)com> writes:
>> On 2013-09-10 12:31:22 +0200, Magnus Hagander wrote:
>>> On Tue, Sep 10, 2013 at 5:29 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>>> I've been thinking of late that it might be time to retire libpq's
>>>> support for V2 protocol (other than in the specific context of the first
>>>> error message received while trying to make a connection).
>
>>> It's probably worth polling for that. I believe the jdbc driver at
>>> least has code for it, but I don't know if it's a requirement at this
>>> point.
>
>> Yes, it has code for it and I think it's still used pretty frequently to
>> circumvent prepared statement planning problems (misestimation,
>> indeterminate types). So I think we need convincing reasons to break
>> their usage.
>
> Note that I was proposing removing libpq's support for V2 connections.
> Not the backend's.

I vote against this. If we remove V2 support from libpq, then we'll
have no easy way to test that the backend's support still works. And
we've got too many people using V2 to think that it's OK not to have
an easy way of testing that. I think the question we ought to be
asking is: how can we get widely-used connectors to stop relying on V2
in the first place?

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company