Date: Tue, 1 Sep 2020 23:22:42 +0200
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
To: Alvaro Herrera <alvherre@2ndquadrant.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>, gkokolatos@pm.me,
	pgsql-hackers@postgresql.org,
	Tatsuro Yamada <tatsuro.yamada.tf@nttcom.co.jp>
Subject: Re: v13: show extended stats target in \d
Message-ID: <20200901212242.hgjpy4wswibjee4f@development>
References: <20200901011429.GZ5450@telsasoft.com>
 <20200901210825.GA20170@alvherre.pgsql>
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On Tue, Sep 01, 2020 at 05:08:25PM -0400, Alvaro Herrera wrote:
>+1 on fixing this, since the ability to change stats target is new in
>pg13.
>
>On 2020-Aug-31, Justin Pryzby wrote:
>
>> Maybe it should have a comma, like ", STATISTICS %s"?
>
>It does need some separator.  Maybe a comma is sufficient, but I'm not
>sure: that will fail when we add cross-relation stats, because the
>FROM clause will have more relations and possibly have commas too.
>
>                                    Table "public.ab1"
> Column |  Type   | Collation | Nullable | Default | Storage | Stats target | Description
>--------+---------+-----------+----------+---------+---------+--------------+-------------
> a      | integer |           |          |         | plain   |              |
> b      | integer |           |          |         | plain   |              |
>Statistics objects:
>    "public"."ab1_a_b_stats" (ndistinct, dependencies, mcv) ON a, b FROM ab1
>
>
>> Also, now I wonder if CREATE STATISTICS should support some syntax to set the
>> initial target.  Like:
>>
>> |CREATE STATISTICS abstats ON a,b FROM child.abc_202006 WITH(STATISTICS 111);
>
>Umm, if true (on which I'm not sold), maybe it should appear in the
>parenthesized list that currently is just the stats type list:
>
> |CREATE STATISTICS abstats (STATISTICS 111) ON a,b FROM child.abc_202006;
>
>I'm not really convinced we need this.
>

Me neither. IMHO it's somewhat similar to per-column statistics target,
where we don't allow specifying that in CREATE TABLE and you have to do

     ALTER TABLE ... ALTER COLUMN ... SET STATISTICS n;

as a separate step.


regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services