Re: PATCH: psql tab completion for SELECT

On 19 January 2018 at 05:37, Vik Fearing <vik(dot)fearing(at)2ndquadrant(dot)com> wrote:
> On 01/18/2018 01:07 AM, Tom Lane wrote:
>> Edmund Horner <ejrh00(at)gmail(dot)com> writes:
>>> On 15 January 2018 at 15:45, Andres Freund <andres(at)anarazel(dot)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.

I'm not sure where we got with this. I really should have put this
patch in a separate thread, since it's an independent feature.

The patch mentioned attempts to put savepoints around the tab
completion query where appropriate.