Re: machine-readable explain output

On Sunday 14 June 2009 07:27:19 Robert Haas wrote:
> On Sat, Jun 13, 2009 at 7:42 PM, Tom Lane<tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> >> In any event, considering that EXPLAIN is a utility statement and
> >> can't be embedded within a query, I'm not sure what benefit we get out
> >> of returning the data as XML rather than text. This doesn't seem
> >> likely to change either, based on Tom's comments here.
> >>
> >> http://archives.postgresql.org/pgsql-hackers/2009-05/msg00969.php
> >
> > I think you misinterpreted the point of that example, which is that
> > there already is a way to get the output of EXPLAIN into the system
> > for further processing. Were this not so, we wouldn't be worrying
> > at all what data type it claims to have. But since there is a way,
> > it's important what data type it produces.
>
> Well, if you get the EXPLAIN output into the system by defining a
> wrapper function, said wrapper function will return the type that it's
> defined to return, regardless of what EXPLAIN itself returns, no?
>
> I don't have a problem making it return XML; I'm just not exactly sure
> how to do it. Is it possible to get that working without depending on
> libxml? How?

Even if this doesn't end up being feasible, I feel it's important that the XML
and JSON formats return one datum, not one per line. Otherwise a client that
wants to do some processing on the result will have to do about three extra
steps to get the result usable.