RE: list of extended statistics on psql - Mailing list pgsql-hackers

Hi, hackers.

I tested this committed feature. 
It doesn't seem to be available to non-superusers due to the inability to access pg_statistics_ext_data. 
Is this the expected behavior?

--- operation ---
postgres=> CREATE STATISTICS stat1_data1 ON c1, c2 FROM data1;
CREATE STATISTICS
postgres=> ANALYZE data1;
ANALYZE
postgres=> SELECT * FROM pg_statistic_ext;
  oid  | stxrelid |   stxname   | stxnamespace | stxowner | stxstattarget | stxkeys | stxkind
-------+----------+-------------+--------------+----------+---------------+---------+---------
 16393 |    16385 | stat1_data1 |         2200 |    16384 |            -1 | 1 2     | {d,f,m}
(1 row)

postgres=> \dX
ERROR:  permission denied for table pg_statistic_ext_data
postgres=>
postgres=> \connect postgres postgres
You are now connected to database "postgres" as user "postgres".
postgres=#
postgres=# \dX
                           List of extended statistics
 Schema |    Name     |    Definition     | Ndistinct | Dependencies |    MCV
--------+-------------+-------------------+-----------+--------------+-----------
 public | stat1_data1 | c1, c2 FROM data1 | built     | built        | requested
(1 row)

--- operation ---

Regards,
Noriyoshi Shinoda

-----Original Message-----
From: Tomas Vondra [mailto:tomas.vondra@enterprisedb.com] 
Sent: Sunday, January 17, 2021 8:32 AM
To: Julien Rouhaud <rjuju123@gmail.com>; Tatsuro Yamada <tatsuro.yamada.tf@nttcom.co.jp>
Cc: Alvaro Herrera <alvherre@2ndquadrant.com>; Tomas Vondra <tomas.vondra@2ndquadrant.com>; Michael Paquier
<michael@paquier.xyz>;Pavel Stehule <pavel.stehule@gmail.com>; PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
 
Subject: Re: list of extended statistics on psql



On 1/15/21 5:19 PM, Tomas Vondra wrote:
> 
> 
> On 1/15/21 9:47 AM, Julien Rouhaud wrote:
>> On Wed, Jan 13, 2021 at 10:22:05AM +0900, Tatsuro Yamada wrote:
>>> Hi Tomas,
>>>
>>> On 2021/01/13 7:48, Tatsuro Yamada wrote:
>>>> On 2021/01/12 20:08, Tomas Vondra wrote:
>>>>> On 1/12/21 2:57 AM, Tatsuro Yamada wrote:
>>>>>> On 2021/01/09 9:01, Tomas Vondra wrote:
>>>>> ...>
>>>>>>> While working on that, I realized that 'defined' might be a bit 
>>>>>>> ambiguous, I initially thought it means 'NOT NULL' (which it does not).
>>>>>>> I propose to change it to 'requested' instead. Tatsuro, do you 
>>>>>>> agree, or do you think 'defined' is better?
>>>>>>
>>>>>> Regarding the status of extended stats, I think the followings:
>>>>>>
>>>>>>    - "defined": it shows the extended stats defined only. We 
>>>>>> can't know
>>>>>>                 whether it needs to analyze or not. I agree this 
>>>>>> name was
>>>>>>                  ambiguous. Therefore we should replace it with a 
>>>>>> more suitable
>>>>>>                 name.
>>>>>>    - "requested": it shows the extended stats needs something. Of 
>>>>>> course,
>>>>>>                 we know it needs to ANALYZE because we can create the patch.
>>>>>>                 However, I feel there is a little ambiguity for DBA.
>>>>>>                 To solve this, it would be better to write an 
>>>>>> explanation of
>>>>>>                 the status in the document. For example,
>>>>>>
>>>>>> ======
>>>>>> The column of the kind of extended stats (e. g. Ndistinct) shows some statuses.
>>>>>> "requested" means that it needs to gather data by ANALYZE. 
>>>>>> "built" means ANALYZE
>>>>>>    was finished, and the planner can use it. NULL means that it doesn't exists.
>>>>>> ======
>>>>>>
>>>>>> What do you think? :-D
>>>>>>
>>>>>
>>>>> Yes, that seems reasonable to me. Will you provide an updated patch?
>>>>
>>>>
>>>> Sounds good. I'll send the updated patch today.
>>>
>>>
>>>
>>> I updated the patch to add the explanation of the extended stats' statuses.
>>> Please feel free to modify the patch to improve it more clearly.
>>>
>>> The attached files are:
>>>     0001: Add psql \dx and the fixed document
>>>     0002: Regression test for psql \dX
>>>     app-psql.html: Created by "make html" command (You can check the
>>>                    explanation of the statuses easily, probably)
>>
>> Hello Yamada-san,
>>
>> I reviewed the patch and don't have specific complaints, it all looks good!
>>
>> I'm however thinking about the "requested" status.  I'm wondering if 
>> it could lead to people think that an ANALYZE is scheduled and will happen soon.
>> Maybe "defined" or "declared" might be less misleading, or even 
>> "waiting for analyze"?
>>
> 
> Well, the "defined" option is not great either, because it can be 
> interpreted as "NOT NULL" - that's why I proposed "requested". Not 
> sure about "declared" - I wouldn't use it in this context, but I'm not 
> a native speaker so maybe it's OK.
> 

I've pushed this, keeping the "requested". If we decide that some other term is a better choice, we can tweak that
laterof course.
 

Thanks Tatsuro-san for the patience!


regards

--
Tomas Vondra
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