Subject: Re: PATCH: psql tab completion for SELECT
To: Tom Lane <tgl@sss.pgh.pa.us>, Edmund Horner <ejrh00@gmail.com>
Cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org,
 pgsql-hackers@postgresql.org
References: 
 <CAMyN-kB_xrU4iYdcF1j=tijgO1DSyjtb3j96O4UEj91XZrZcMg@mail.gmail.com>
 <CAMyN-kCr6aUFaE=ov+_r=b4nS_ihtmJ8-MLMoomZGWdNFgMaVw@mail.gmail.com>
 <F9466A55-8F16-4DC2-BAE8-6386870A3C3C@anarazel.de>
 <CAMyN-kC65Xdn3Y5A+muYWMAR50gk-oCABcyZ809wuV0x9_nsJQ@mail.gmail.com>
 <882D6617-FA16-4C56-8FE0-884BCBBE5A4C@anarazel.de>
 <CAMyN-kAJX9fkzm1aFE5sp4se9t1c+p1e1JJGc_MXerxHUK9qoQ@mail.gmail.com>
 <2738.1516234038@sss.pgh.pa.us>
From: Vik Fearing <vik.fearing@2ndquadrant.com>
Organization: 2ndQuadrant France
Message-ID: <3a919958-e508-3b66-686f-44a7937fb6e7@2ndquadrant.com>
Date: Thu, 18 Jan 2018 17:37:30 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101
 Thunderbird/52.5.0
MIME-Version: 1.0
In-Reply-To: <2738.1516234038@sss.pgh.pa.us>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Precedence: bulk

On 01/18/2018 01:07 AM, Tom Lane wrote:
> Edmund Horner <ejrh00@gmail.com> writes:
>> On 15 January 2018 at 15:45, Andres Freund <andres@anarazel.de> wrote:
>>> All worries like this are supposed to check the server version.
> 
>> In psql there are around 200 such tab completion queries, none of
>> which checks the server version.  Many would cause the user's
>> transaction to abort if invoked on an older server.  Identifying the
>> appropriate server versions for each one would be quite a bit of work.
> 
>> Is there a better way to make this more robust?
> 
> Maybe it'd be worth the effort to wrap tab completion queries in
> SAVEPOINT/RELEASE SAVEPOINT if we're inside a user transaction
> (which we could detect from libpq's state, I believe).
> 
> That seems like an independent patch, but it'd be a prerequisite
> if you want to issue tab completion queries with version dependencies.
> 
> A bigger point here is: do you really want SELECT tab completion
> to work only against the latest and greatest server version?
> That would become an argument against committing the feature at all;
> maybe not enough to tip the scales against it, but still a demerit.

I don't really want such a patch.  I use new psql on old servers all the
time.
-- 
Vik Fearing                                          +33 6 46 75 15 36
http://2ndQuadrant.fr     PostgreSQL : Expertise, Formation et Support