Thread: pg_dump shared locks documentation

Hi, 

In the `pg_dump` documentation we talk about "shared locks", but IIUC, we actually take `AccessShareLock`s. 
This might be misunderstood with the `ShareLock`.

There are 5 occurrences. 4 in `--jobs=njobs` and 1 in `--lock-wait-timeout=timeout` sections. 

Cheers,  
Florin Irion

On 2022-Mar-15, Florin Irion wrote:

> In the `pg_dump` documentation we talk about "shared locks", but IIUC,
> we actually take `AccessShareLock`s.  This might be misunderstood with
> the `ShareLock`.

This might be a bit excessive to have in the main text.  What about
adding a footnote to point out the exact lock level that is meant, with
a link to the server doc page that explains each lock level?
Something like this:

>          Requesting exclusive locks on database objects while running a parallel dump could
>          cause the dump to fail. The reason is that the <application>pg_dump</application> leader process
> -        requests shared locks on the objects that the worker processes are going to dump later
> +        requests shared locks<footnote>The precise lock level used is <literal>ACCESS SHARE</literal>.
> +        See <xref ... /> for more information.</footnote> on the objects that the worker processes are
>          going to dump later

...

> @@ -870,7 +870,7 @@ PostgreSQL documentation
>        <term><option>--lock-wait-timeout=<replaceable class="parameter">timeout</replaceable></option></term>
>        <listitem>
>         <para>
> -        Do not wait forever to acquire shared table locks at the beginning of

Same here.

-- 
Álvaro Herrera

Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
> This might be a bit excessive to have in the main text.  What about
> adding a footnote to point out the exact lock level that is meant, with
> a link to the server doc page that explains each lock level?

I dunno how well <footnote> will render in man-page format.
How about just inserting a parenthetical remark at the first usage?

... leader process requests shared locks (ACCESS SHARE) on the ...

Possibly we could make the "ACCESS SHARE" be a <link> without causing
problems in man format.

            regards, tom lane

On 15/03/22 16:55, Tom Lane wrote:
> Alvaro Herrera <alvherre@alvh.no-ip.org> writes:
>> This might be a bit excessive to have in the main text.  What about
>> adding a footnote to point out the exact lock level that is meant, with
>> a link to the server doc page that explains each lock level?
> 
> I dunno how well <footnote> will render in man-page format.
> How about just inserting a parenthetical remark at the first usage?
> 
> ... leader process requests shared locks (ACCESS SHARE) on the ...
> 
> Possibly we could make the "ACCESS SHARE" be a <link> without causing
> problems in man format.
> 
>             regards, tom lane

Makes sense.
I tried the footnote and in fact, it doesn't render well in the man page. It just adds a blank line(at least how I
triedit).
 

So, I made the link to ACCESS SHARE, pointing to section 13.3.1. "Table-Level Locks" , was this what you had in mind? 

V2 attached. 

Thank you for looking into this.
Florin Irion

On Tue, Mar 15, 2022 at 11:21:41PM +0100, Florin Irion wrote:
> So, I made the link to ACCESS SHARE, pointing to section 13.3.1. "Table-Level Locks" , was this what you had in mind?

> 
> V2 attached. 

LGTM.  I've marked the commitfest entry as ready-for-committer.

-- 
Nathan Bossart
Amazon Web Services: https://aws.amazon.com