Re: machine-readable explain output v2

Hi Robert, Hi all,

explain_format_infrastructure-v2.patch:
Applies cleanly, code changes look sensible, no behaviour changes.

explain_format-v2.patch
Applies after trivial conflicts (updated version attached). Once more the code
changes look sensible to me, except maybe that I don't like the codeflow at
some parts. That's partially related due to having to generate xml/json output
by hand...

One part where I find the code flow ugly is 'did_boilerplate' in
report_triggers/its callsites.
I can see why it is done that way, but its not exactly obvious to read when
you want to find out how the format looks.

Another, minor, issue is that the patch changes the FORMAT TEXT/default output
if VERBOSE is specified (schema is added). I don't see that as a real problem
because the format for VERBOSE is new anyway, but I thought I would mention
it.

XML Format:
As discussed previously I would like the format to look a bit different - but
everyone wants it to look different anyway, so I think its ok as one of
multiple possible lowest common determinators... With the big advantage of
already being implemented.

I think it would be nice in the future to add some sort of
'category={planner,timing,..}' attribute, but I think that should be
discussed/implemented separately.

Documentation:
I think it would be nice to add some more documentation about the xml format
for application writers, but I think this should be a separate patch anyway.

I did not yet look at the contrib/autoexplain portions. Will do that on Monday
or so.

Andres