Re: RFC: Logging plan of the running query

On 2021-07-28 03:45, Pavel Stehule wrote:
> út 27. 7. 2021 v 20:34 odesílatel Fujii Masao
> <masao(dot)fujii(at)oss(dot)nttdata(dot)com> napsal:
>
>> On 2021/07/09 14:05, torikoshia wrote:
>>> On 2021-07-02 23:21, Bharath Rupireddy wrote:
>>>> On Tue, Jun 22, 2021 at 8:00 AM torikoshia
>> <torikoshia(at)oss(dot)nttdata(dot)com> wrote:
>>>>> Updated the patch.
>>>>
>>>> Thanks for the patch. Here are some comments on the v4 patch:
>>>
>>> Thanks for your comments and suggestions!
>>> I agree with you and updated the patch.
>>>
>>> On Thu, Jul 1, 2021 at 3:34 PM Fujii Masao
>> <masao(dot)fujii(at)oss(dot)nttdata(dot)com> wrote:
>>>
>>>> DO $$
>>>> BEGIN
>>>> PERFORM pg_sleep(100);
>>>> END$$;
>>>>
>>>> When I called pg_log_current_query_plan() to send the signal to
>>>> the backend executing the above query, I got the following log
>> message.
>>>> I think that this is not expected message. I guess this issue
>> happened
>>>> because the information about query text and plan is retrieved
>>>> from ActivePortal. If this understanding is right, ISTM that we
>> should
>>>> implement new mechanism so that we can retrieve those information
>>>> even while nested query is being executed.
>>>
>>> I'm now working on this comment.
>>
>> One idea is to define new global pointer, e.g., "QueryDesc
>> *ActiveQueryDesc;".
>> This global pointer is set to queryDesc in ExecutorRun()
>> (also maybe ExecutorStart()). And this is reset to NULL in
>> ExecutorEnd() and
>> when an error is thrown. Then ProcessLogCurrentPlanInterrupt() can
>> get the plan of the currently running query from that global pointer
>> instead of ActivePortal, and log it. Thought?
>
> It cannot work - there can be a lot of nested queries, and at the end
> you cannot reset to null, but you should return back pointer to outer
> query.

Thanks for your comment!

I'm wondering if we can avoid this problem by saving one outer level
QueryDesc in addition to the current one.
I'm going to try it.

--
Regards,

--
Atsushi Torikoshi
NTT DATA CORPORATION