Date: Fri, 21 Jan 2022 12:02:00 -0600
From: Justin Pryzby <pryzby@telsasoft.com>
To: Tomas Vondra <tomas.vondra@enterprisedb.com>
Cc: =?iso-8859-1?Q?=C1lvaro?= Herrera <alvherre@alvh.no-ip.org>,
	yuzuko <yuzukohosoya@gmail.com>, pgsql-hackers@postgresql.org
Subject: Re: document the need to analyze partitioned tables
Message-ID: <20220121180200.GM23027@telsasoft.com>
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 <20211008125822.GJ27491@telsasoft.com>
 <681e76ad-3a7b-ea3c-b6b0-55946239c49b@enterprisedb.com>
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Thanks for looking at this

On Fri, Jan 21, 2022 at 06:21:57PM +0100, Tomas Vondra wrote:
> Hi,
> 
> On 10/8/21 14:58, Justin Pryzby wrote:
> > Cleaned up and attached as a .patch.
> > 
> > The patch implementing autoanalyze on partitioned tables should
> > revert relevant portions of this patch.
> 
> I went through this patch and I'd like to propose a couple changes, per the
> 0002 patch:
> 
> 1) I've reworded the changes in maintenance.sgml a bit. It sounded a bit
> strange before, but I'm not a native speaker so maybe it's worse ...

+     autoanalyze on the parent table.  If your queries require statistics on                                                                       
+     parent relations for proper planning, it's necessary to periodically run                                                                      

You added two references to "relations", but everything else talks about
"tables", which is all that analyze processes.

> 2) Remove unnecessary whitespace changes in perform.sgml.

Those were a note to myself and to any reviewer - should that be updated too ?

> 3) Simplify the analyze.sgml changes a bit - it was trying to cram too much
> stuff into a single paragraph, so I split that.
> 
> Does that seem OK, or did omit something important?

+    If the table being analyzed has one or more children,

I think you're referring to both legacy inheritance and and partitioning.  That
should be more clear.

+    <command>ANALYZE</command> gathers two sets of statistics: once on the rows
+    of the parent table only, and a second one including rows of both the parent
+    table and all child relations.  This second set of statistics is needed when

I think should say ".. and all of its children".

> FWIW I think it's really confusing we have inheritance and partitioning, and
> partitions and child tables. And sometimes we use partitioning in the
> generic sense (i.e. including the inheritance approach), and sometimes only
> the declarative variant. Same for partitions vs child tables. I can't even
> imagine how confusing this has to be for people just learning this stuff.
> They must be in permanent WTF?! state ...

The docs were cleaned up some in 0c06534bd.  At least the word "partitioned"
should never be used for legacy inheritance - but "partitioning" is.

-- 
Justin