Re: REVIEW: EXPLAIN and nfiltered

On Thu, Jan 20, 2011 at 12:57 PM, Magnus Hagander <magnus@hagander.net> wrote:
>
> On Jan 20, 2011 6:43 PM, "Tom Lane" <tgl@sss.pgh.pa.us> wrote:
>>
>> Robert Haas <robertmhaas@gmail.com> writes:
>> > On Thu, Jan 20, 2011 at 11:55 AM, Stephen Frost <sfrost@snowman.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..

How much has that code been updated from one release to the next?

--
Robert Haas
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