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

(2014/09/10 12:31), Fujii Masao wrote:
> On Wed, Sep 10, 2014 at 12:15 PM, Etsuro Fujita
> <fujita.etsuro@lab.ntt.co.jp> wrote:
>> (2014/09/09 22:17), Fujii Masao wrote:
>>> Attached is the updated version of the patch.

>> I took a quick review on the patch.  It looks good to me,

>> but one thing I'm
>> concerned about is
>>
>> You wrote:
>>>>>> The attached patch introduces the GIN index storage parameter
>>>>>> "PENDING_LIST_CLEANUP_SIZE" which specifies the maximum size of
>>>>>> GIN pending list. If it's not set, work_mem is used as that maximum
>>>>>> size,
>>>>>> instead. So this patch doesn't break the existing application which
>>>>>> currently uses work_mem as the threshold of cleanup operation of
>>>>>> the pending list. It has only not to set PENDING_LIST_CLEANUP_SIZE.
>>
>> As you mentioned, I think it's important to consider for the existing
>> applications, but I'm wondering if it would be a bit confusing users to have
>> two parameters,
>
> Yep.
>
>> 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...

Why not use ALTER INDEX ... SET (PENDING_LIST_CLEANUP_SIZE= ...)?  Maybe 
I'm missing something, though.

> 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.

Yeah, that's an idea.  So, I'd like to hear the opinions of others.

Thanks,

Best regards,
Etsuro Fujita