Обсуждение: Re: Missing mention of autovacuum_work_mem

Hi,

There was no follow up to my message below so I'm raising it again.


I can see in
src/backend/access/heap/vacuumlazy.c
that compute_max_dead_tuples uses autovacuum_work_mem when it is given.


> The "vacuuming indexes" documentation has:
>

> "If a table has any indexes, this will happen at least once per vacuum,
> after the heap has been completely scanned. It may happen multiple times per
> vacuum if maintenance_work_mem is insufficient to store the number of dead
> tuples found."
>

> should be something like
>


(I've changed this slightly and removed maximum as it seems redundant)

"If a table has any indexes, this will happen at least once per vacuum,
after the heap has been completely scanned. It may happen multiple times per
vacuum if the memory is insufficient to store the number of dead
tuples found. The memory is set via the maintenance_work_mem unless
it is an autovacuum then autovacuum_work_mem will be used."

On Mon, 2021-09-20 at 08:07 +0000, nikolai.berkoff wrote:
> I can see in
> src/backend/access/heap/vacuumlazy.c
> that compute_max_dead_tuples uses autovacuum_work_mem when it is given.
>
> The "vacuuming indexes" documentation has:
>
> > "If a table has any indexes, this will happen at least once per vacuum,
> > after the heap has been completely scanned. It may happen multiple times per
> > vacuum if maintenance_work_mem is insufficient to store the number of dead
> > tuples found."

Your suggested change is:

> "If a table has any indexes, this will happen at least once per vacuum,
> after the heap has been completely scanned. It may happen multiple times per
> vacuum if the memory is insufficient to store the number of dead
> tuples found. The memory is set via the maintenance_work_mem unless
> it is an autovacuum then autovacuum_work_mem will be used."

Why not keep it simple with

"If a table has any indexes, this will happen at least once per vacuum,
 after the heap has been completely scanned. It may happen multiple times per
 vacuum if maintenance_work_mem (or, in the case of autovacuum,
 autovacuum_work_mem) is insufficient to store the number of dead
 tuples found."

Yours,
Laurenz Albe
-- 
Cybertec | https://www.cybertec-postgresql.com

> Why not keep it simple with
>

> "If a table has any indexes, this will happen at least once per vacuum,
>

> after the heap has been completely scanned. It may happen multiple times per
>

> vacuum if maintenance_work_mem (or, in the case of autovacuum,
>

> autovacuum_work_mem) is insufficient to store the number of dead
>

> tuples found."

Thank you Laurenz,

Yes that reads better still.

Regards,

Nikolai

Yes that reads better still.

On Wed, 2021-09-22 at 17:45 -0300, Euler Taveira wrote:
> On Mon, Sep 20, 2021, at 10:40 AM, nikolai.berkoff wrote:
> > Yes that reads better still.
> I'm attaching a patch with Laurenz's words.

Thanks, and +1 from me.

Yours,
Laurenz Albe

On Thu, Sep 23, 2021 at 10:48:37AM +0200, Laurenz Albe wrote:
> Thanks, and +1 from me.

maintenance_work_mem would be used in the context of autovacuum if
autovacuum_work_mem is -1, but it seems to me that the suggested
wording sounds like only autovacuum_work_mem is used and that it would
never fall back to maintenance_work_mem, no?  I would suggest the
addition of "if specified" in the new part within parenthesis
--
Michael

On Thu, Sep 23, 2021 at 10:48:37AM +0200, Laurenz Albe wrote:

> Thanks, and +1 from me.

maintenance_work_mem would be used in the context of autovacuum if

autovacuum_work_mem is -1, but it seems to me that the suggested

wording sounds like only autovacuum_work_mem is used and that it would

never fall back to maintenance_work_mem, no?  I would suggest the

addition of "if specified" in the new part within parenthesis

On Fri, Sep 24, 2021 at 12:21:40PM -0300, Euler Taveira wrote:
> Good point. However, I prefer "if set".

WFM.
--
Michael

On Sat, Sep 25, 2021 at 07:51:15AM +0900, Michael Paquier wrote:
> WFM.

This has been applied and backpatched as of 1ba8410.
--
Michael

On Mon, 2021-09-27 at 09:25 +0900, Michael Paquier wrote:
> On Sat, Sep 25, 2021 at 07:51:15AM +0900, Michael Paquier wrote:
> > WFM.
> 
> This has been applied and backpatched as of 1ba8410.

Thank you!

Yours,
Laurenz Albe