Re: psql \G command -- send query and output using extended format - Mailing list pgsql-hackers

On Thu, Apr 3, 2008 at 6:44 PM, Alvaro Herrera
<alvherre@commandprompt.com> wrote:
> Bruce Momjian escribió:
>
>
>  > It seems more helpful if there were \x option to use extended format
>  > only when the output is too wide.  TODO already has:
>  >
>  >         o Add auto-expanded mode so expanded output is used if the row
>  >           length is wider than the screen width.
>  >
>  >           Consider using auto-expanded mode for backslash commands like \df+.
>
>  Some sort of "\x auto"?  Sounds interesting ...

Hmm, seems doable.

While writing the \G patch I wanted to keep the changes to minimum, so it would
be clear what gets done.  What I don't like about that patch is that
I've added in
struct _printTableOpt another bool "extend_once" after the "extend" bool.

I think there should be a format Enum, which would take values like NORMAL,
EXTENDED, and EXTENDED_ONCE -- but this would be a much more invasive patch.
Oh, and coincidentally its where AUTO format should go. :)

Now, assuming we want "\x auto" there are couple of things to discuss
before actually coding.

1. Adding "\x auto" changes how "\x" (and \pset).  Currently we accept:\x -  toggle between on and off\x off - turn
extendedformat off\x anything - turn extended format on. 
if doing, auto we need to change it to something like,\x - toggle between on and off, if in "auto", toggle to "off"\x
on- extended format on\x off - extended format off\x auto - auto extended format\x anything else - extended format on
witha "depreciated" warning. 

2. Do we want \G?  I would say "yes". ;) But it should get discussed.
pgsql-general perhaps?

3. We should decide how each of the "commands" work in auto mode.
I think it should be something like: "if output is less or equal than
screen width -- use normal mode, else extended".  I we have \g and \G,
they should be handled a bit differently in auto mode:";" -- perform automatic format adjustment"\g" -- force normal
mode(probably for file-output)"\G" -- force extended mode (probably for file-output). 
I especially would like an opinion on this from you.

4. And as for using "\x" for the one-shot expanded output, I think it would
be possible to allow queries like: SELECT * FROM foo\x
...but I think fundamental problem with this approach is that it promotes
"\x" to be able to submit query.  I don't think its a good idea.
  Regards,     Dawid