Re: pgbench - allow backslash continuations in \set expressions

On Fri, Dec 2, 2016 at 6:13 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Fabien COELHO <coelho(at)cri(dot)ensmp(dot)fr> writes:
> >> In psql, if backslash followed by [CR]LF is interpreted as a
> >> continuation symbol, commands like these seem problematic
> >> on Windows since backslash is the directory separator:
> >>
> >> \cd \
> >> \cd c:\somepath\
> >>
> >> Shell invocations also come to mind:
> >> \! dir \
>
> > Thanks for pointing out these particular cases. I was afraid of such
> > potential issues, hence my questions...
>
> Those look like nasty counterexamples, but I think they are not, because
> they don't work today. What you get is
>
> regression=# \cd \
> Invalid command \. Try \? for help.
>
> AFAICT you would need to write it
>
> regression=# \cd '\\'
> \cd: could not change directory to "\": No such file or directory
>
> (That's on Unix of course, on Windows I'd expect it to succeed.)
>
> The reason for this is that psql already has a policy that an unquoted
> backslash begins a new backslash command on the same line. Since
> there is no command named backslash-return, this is available syntax
> that can be repurposed in the direction we want.
>
> I believe that we need to do basically the same thing in pgbench, and
> I'm fine with that because I think we should have an overall policy of
> synchronizing the psql and pgbench metacommand syntaxes as best we can.
> This will at some point necessitate invention of a quoting rule for
> pgbench metacommand arguments, so that you can write a backslash as part
> of an argument when you need to. We might not need to do that today
> (as I'm not sure there are any use-cases for one), but maybe it'd be best
> to just bite the bullet and put it in.
>
>
The review from the committer is arrived at the end of commitfest,
so moved the patch into next CF with "waiting on author" status.

Regards,
Hari Babu
Fujitsu Australia