Re: Autovacuum launcher occurs error when cancelled by SIGINT

On Thu, Jun 22, 2017 at 9:48 AM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
> On Thu, Jun 22, 2017 at 1:29 AM, Kuntal Ghosh
> <kuntalghosh(dot)2007(at)gmail(dot)com> wrote:
>> On Wed, Jun 21, 2017 at 7:52 PM, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>>> On Wed, Jun 21, 2017 at 7:47 PM, Kuntal Ghosh
>>> <kuntalghosh(dot)2007(at)gmail(dot)com> wrote:
>>>>> IMHO, It's not a good idea to use DSM call to verify the DSA handle.
>>>>>
>>>> Okay. Is there any particular scenario you've in mind where this may fail?
>>>
>>> It's not about failure, but about the abstraction. When we are using
>>> the DSA we should not directly access the DSM which is under DSA.
>>>
>> Okay. I thought that I've found at least one usage of
>> dsm_find_mapping() in the code. :-)
>>
>> But, I've some more doubts.
>> 1. When should we use dsm_find_mapping()? (The first few lines of
>> dsm_attach is same as dsm_find_mapping().)
>> 2. As a user of dsa, how should we check whether my dsa handle is
>> already attached? I guess this is required because, if a user tries to
>> re-attach a dsa handle, it's punishing the user by throwing an error
>> and the user wants to avoid such errors.
>
> From a logical point of view, there is nothing preventing the use of
> dsm_find_mapping() on a DSA handle, still the API layering looks wrong
> if you want to check for an existing mapping. So why not defining a
> new API, like dsa_find_mapping() that just wraps dsm_find_mapping()
> but has its own error handling? This would offer more flexibility for
> the future.
Yeah. That sounds reasonable. Or, dsa_attach can throw error conditionally.

--
Thanks & Regards,
Kuntal Ghosh
EnterpriseDB: http://www.enterprisedb.com