Re: PENDING_LIST_CLEANUP_SIZE - maximum size of GIN pending list Re: HEAD seems to generate larger WAL regarding GIN index

(2014/09/13 2:42), Fujii Masao wrote:
> On Wed, Sep 10, 2014 at 10:37 PM, Alvaro Herrera
> <alvherre(at)2ndquadrant(dot)com> wrote:
>> Fujii Masao wrote:
>>> On Wed, Sep 10, 2014 at 12:15 PM, Etsuro Fujita
>>> <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> wrote:
>>
>>>> PENDING_LIST_CLEANUP_SIZE and work_mem, for this setting.
>>>> Wouldn't it be easy-to-use to have only one parameter,
>>>> PENDING_LIST_CLEANUP_SIZE? How about setting PENDING_LIST_CLEANUP_SIZE to
>>>> work_mem as the default value when running the CREATE INDEX command?
>>>
>>> That's an idea. But there might be some users who want to change
>>> the cleanup size per session like they can do by setting work_mem,
>>> and your idea would prevent them from doing that...
>>>
>>> So what about introduing pending_list_cleanup_size also as GUC?
>>> That is, users can set the threshold by using either the reloption or
>>> GUC.
>>
>> Yes, I think having both a GUC and a reloption makes sense -- the GUC
>> applies to all indexes, and can be tweaked for individual indexes using
>> the reloption.
>
> Agreed.
>
>> I'm not sure about the idea of being able to change it per session,
>> though. Do you mean that you would like insert processes use a very
>> large value so that they can just append new values to the pending list,
>> and have vacuum use a small value so that it cleans up as soon as it
>> runs? Two things: 1. we could have an "autovacuum_" reloption which
>> only changes what autovacuum does; 2. we could have autovacuum run
>> index cleanup actions separately from actual vacuuming.
>
> Yes, I was thinking something like that. But if autovacuum
> has already been able to handle that, it's nice. Anyway,
> as you pointed out, it's better to have both GUC and reloption
> for the cleanup size of pending list.

OK, I'd vote for your idea of having both the GUC and the reloption.
So, I think the patch needs to be updated. Fujii-san, what plan do you
have about the patch?

Sorry for the delay.

Thanks,

Best regards,
Etsuro Fujita