Re: psql metaqueries with \gexec

On Sun, Apr 3, 2016 at 4:26 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > Jim, can you re-review this?
>
> I'm not Jim, but I have a question: what's the motivation for the
> Fortran-order traversal of the result (down rows before across columns)?
> It seems less than intuitive to do it that way. Perhaps there's a good
> reason, but I do not see any defense of this choice in the thread.
>

If I am understanding you correctly, it does work the way you find
intuitive: all results from the first row are executed before any in the
second row, so

SELECT a, b UNION ALL SELECT c, d

will execute the queries in order: a, b, c, d as is shown in the changes to
the sgml and the test cases.

Did you get the impression of Fortran-ordering from the phrase
"top-to-bottom, left-to-right order" in the sgml patch? If so, would
calling it "rows first" or something else be more clear?

Or am I misunderstanding you and you find the order a, c, b, d more
intuitive?

I also note that the patch seems to be missing resetting gexec_flag
> in some error exit paths, possibly allowing the \gexec to be applied
> to the next query unexpectedly. It should clear that in all the same
> places where gfname or gset_prefix get cleared.
>

Will do!

I'm only seeing one place where those two vars are deallocated and nulled,
and that's at the tail end of SendQuery. Were you expecting more than just
that?