Re: pgbench - allow to store select results into variables

On Wed, Jul 13, 2016 at 3:02 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>> On Sat, Jul 9, 2016 at 7:52 AM, Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> wrote:
>>> If someone thinks that "gset" is a good idea for pgbench, which I don't, it
>>> could be implemented. I think that an "into" feature, like PL/pgSQL & ECPG,
>>> makes more sense for scripting.
>
>> I agree: I like \into.
>
>> But:
>
>>> SELECT 1, 2 \; SELECT 3;
>>> \into one two three
>
>> I think that's pretty weird.
>
> Yeah, that's seriously nasty action-at-a-distance in my view. I'd be okay
> with
>
> SELECT 1, 2 \into one two
> SELECT 3 \into three
>
> but I do not think that a metacommand on a following line should
> retroactively affect the execution of a prior command, much less commands
> before the last one. Even if this happens to be easy to do in pgbench's
> existing over-contorted logic, it's tremendously confusing to the user;
> and it might be much less easy if we try to refactor that logic.
>
> And I'm with Pavel on this: it should work exactly like \gset. Inventing
> \into to do almost the same thing in a randomly different way exhibits a
> bad case of NIH syndrome. Sure, you can argue about how it's not quite
> the same use-case and so you could micro-optimize by doing it differently,
> but that's ignoring the cognitive load on users who have to remember two
> different commands. Claiming that plpgsql's SELECT INTO is a closer
> analogy than psql's \gset is quite bogus, too: the environment is
> different (client side vs server side, declared vs undeclared target
> variables), and the syntax is different (backslash or not, commas or not,
> just for starters). I note also that we were talking a couple months ago
> about trying to align psql and pgbench backslash commands more closely.
> This would not be a good step in that direction.

True, but I'd still argue that \into is a lot more readable than
\gset. Maybe both programs should support both commands.

--
Robert Haas
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