Re: Review: Display number of changed rows since last analyze

On Mon, Jul 1, 2013 at 3:15 PM, Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at> wrote:
> Magnus Hagander wrote:
>>>> On Mon, Jun 17, 2013 at 1:49 PM, Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at> wrote:
>>>>> I think that the column name is ok as it is, even if it
>>>>> is a bit long - I cannot come up with a more succinct
>>>>> idea. Perhaps "n_changed_since_analyze" could be shortened
>>>>> to "n_mod_since_analyze", but that's not much of an improvement.
>>>>
>>>> AFAICT it's related to "n_live_tup", and "n_dead_tup". How about just
>>>> "n_mod_tup"? Though that doesn't convey that it's since the last
>>>> analyze, I guess.
>>>>
>>>> But given that both n_dead_tup and n_live_tup don't really indicate
>>>> that they're not "since the beginning of stats" in the name (which
>>>> other stats counters are), I'm not sure that's a problem? It would be
>>>> a name that sounds more similar to the rest of the table.
>>>
>>> I don't get that.
>>>
>>> As far as I know, n_dead_tup and n_live_tup are estimates for
>>> the total number of live and dead tuples, period.
>>>
>>> Both numbers are not reset to zero when ANALYZE (or even VACUUM)
>>> takes place.
>>
>> No, but they are zero *until* vacuum runs.
>>
>> The point I was trying to make was that they are showing an absolute
>> number. Unlike for example n_tup_inserted and friends which show the
>> total number of <event> since stat reset.
>
> Ok, I understand you now.
>
> All the old names are fairly intuitive in my opinion.
>
> "Number of life tuples since the statistics were reset" doesn't make
> a lot of sense to me, so I would automatically read that as an absolute
> number.
>
> But it would not be clear to me that "n_mod_tuples" are counted
> since the last ANALYZE (different from other columns); I would
> jump to the conclusion that it is a sum of n_tup_ins, n_tup_upd
> and n_tup_del.
>
> So I think that a name that it less likely to cause confusion
> would be better that a short, but misleading name.

Yeah, you're probably right. Applied with your suggested name, and
some further minor tweaking on the wording in the docs.

Thanks!

--
Magnus Hagander
Me: http://www.hagander.net/
Work: http://www.redpill-linpro.com/