Re: REVIEW: EXPLAIN and nfiltered

On Jan 20, 2011 6:43 PM, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
> > On Thu, Jan 20, 2011 at 11:55 AM, Stephen Frost <sfrost(at)snowman(dot)net>
wrote:
> >> While I agree completely about the general "if you're going to break,
> >> break it big" approach, but I don't particularly care for holding
output
> >> strings from EXPLAIN to the same level that we do the wireline
protocol.
>
> > I agree; we make bigger changes than this all the time.
>
> No, we don't. It's true that a client that wants to truly *understand*
> the plan has to know a lot of things, but the fundamental format of
> EXPLAIN ANALYZE output has been real stable for a real long time:
>
> node name (cost=xxx.xx..xxx.xx rows=xxx width=xxx) (actual
time=xxx.xxx..xxx.xxx rows=xxx loops=xxx)
> detail line: something or other
> -> subnode name ... more of the same ...
>
> This level of understanding seems plenty sufficient for something like
> explain.depesz.com, to name just one popular tool. The last format
> change of any kind we made in this skeleton was to increase the number
> of decimal places in the "actual time" numbers from 2 to 3 (wow).
> That was in 7.4. Modulo that detail, this basic contract has been valid
> since EXPLAIN ANALYZE was invented, in 7.2. As proposed, this patch
> will break it.
>
> It might be interesting for somebody to go look at Hubert's code and see
> just how much it really knows about the EXPLAIN output format, and how
> much it's had to change across PG releases.
>

Haven't looked at what changes with this patch, but dont forget PgAdmin that
also parses the output. Though if the format changes enough to affect it,
that might be the driving force to have it use xml format instead, which is
the one that is intended for machine parsing after all..

/Magnus