From: Tom Lane <tgl@sss.pgh.pa.us>
To: Edmund Horner <ejrh00@gmail.com>
cc: Andres Freund <andres@anarazel.de>, pgsql-hackers@lists.postgresql.org,
        pgsql-hackers@postgresql.org
Subject: Re: PATCH: psql tab completion for SELECT
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Comments: In-reply-to Edmund Horner <ejrh00@gmail.com>
	message dated "Thu, 18 Jan 2018 10:47:11 +1300"
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Date: Wed, 17 Jan 2018 19:07:18 -0500
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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.

			regards, tom lane