Re: pgbench - add \aset to store results of a combined query

V2 is a rebase.

> A long time ago I submitted a pgbench \into command to store results of 
> queries into variables independently of the query being processed, which got 
> turn into \gset (;) and \cset (\;), which got committed, then \cset was 
> removed because it was not "up to standard", as it could not work with empty 
> query (the underlying issue is that pg silently skips empty queries, so that 
> "\; SELECT 1 \; \; SELECT 3," returns 2 results instead of 4, a misplaced 
> optimisation from my point of view).
>
> Now there is a pgbench \gset which allows to extract the results of variables 
> of the last query, but as it does both setting and ending a query at the same 
> time, there is no way to set variables out of a combined (\;) query but the 
> last, which is the kind of non orthogonal behavior that I dislike much.
>
> This annoys me because testing the performance of combined queries cannot be 
> tested if the script needs to extract variables.
>
> To make the feature somehow accessible to combined queries, the attached 
> patch adds the "\aset" (all set) command to store all results of queries 
> which return just one row into variables, i.e.:
>
>  SELECT 1 AS one \;
>  SELECT 2 AS two UNION SELECT 2 \;
>  SELECT 3 AS three \aset
>
> will set both "one" and "three", while "two" is not set because there were 
> two rows. It is a kind of more permissive \gset.
>
> Because it does it for all queries, there is no need for synchronizing with 
> the underlying queries, which made the code for \cset both awkward and with 
> limitations. Hopefully this version might be "up to standard".
> I'll see. I'm in no hurry:-)
>
>

-- 
Fabien.