Re: list of extended statistics on psql

From: Tatsuro Yamada <tatsuro(dot)yamada(dot)tf(at)nttcom(dot)co(dot)jp>
To: Tomas Vondra <tomas(dot)vondra(at)enterprisedb(dot)com>, Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
Cc: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz>, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>, Julien Rouhaud <rjuju123(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: list of extended statistics on psql
Date: 2021-01-13 01:22:05
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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)

Tatsuro Yamada

Attachment Content-Type Size
0001-psql-dX-list-extended-statistics-objects-20210113.patch text/plain 10.2 KB
0002-regression-test-for-psql-dX-20210113.patch text/plain 9.8 KB
app-psql.html text/html 206.1 KB

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