Re: Report planning memory in EXPLAIN ANALYZE

I think this patch is mostly OK and decided to use it to test something
else. In doing so I noticed one small thing that bothers me: if
planning uses buffers, and those were requested to be reported, we get
something like this at the end of the explain

Planning:
Buffers: shared hit=120 read=30
Planning Memory: used=67944 bytes allocated=73728 bytes
Planning Time: 0.892 ms

This looks a bit unpleasant. Wouldn't it be much nicer if the Planning
thingies were all reported together in the Planning group?

Planning:
Buffers: shared hit=120 read=30
Memory: used=67944 bytes allocated=73728 bytes
Time: 0.892 ms

This is easier said than done. First, moving "Time" to be in the same
group would break tools that are already parsing the current format. So
maybe we should leave that one alone. So that means we end up with
this:

Planning:
Buffers: shared hit=120 read=30
Memory: used=67944 bytes allocated=73728 bytes
Planning Time: 0.892 ms

Better than the original, I think, even if not perfect. Looking at the
code, this is a bit of a mess to implement, because of the way
show_buffer_usage is coded; currently it has an internal
increment/decrement of indentation, so in order to report memory we
would have to move the indentation change to outside show_buffer_usage
(I think it does belong outside, but the determination of whether to
print or not is quite messy, so we'd need a new function returning
boolean).

Alternatively we could move the memory reportage to within
show_buffer_usage, but that seems worse.

Or we could leave it as you have it, but to me that's akin to giving up
on doing it nicely.

--
Álvaro Herrera Breisgau, Deutschland — https://www.EnterpriseDB.com/
"I think my standards have lowered enough that now I think 'good design'
is when the page doesn't irritate the living f*ck out of me." (JWZ)