Re: document the need to analyze partitioned tables

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