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

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.

Yours,
Laurenz Albe