Re: On-demand running query plans using auto_explain and signals

2015-09-08 18:53 GMT+02:00 Shulgin, Oleksandr <oleksandr(dot)shulgin(at)zalando(dot)de>
:

> On Tue, Sep 8, 2015 at 11:49 AM, Shulgin, Oleksandr <
> oleksandr(dot)shulgin(at)zalando(dot)de> wrote:
>
>>
>> >> The real problem could be if the process that was signaled to connect
>> to the message queue never handles the interrupt, and we keep waiting
>> forever in shm_mq_receive(). We could add a timeout parameter or just let
>> the user cancel the call: send a cancellation request, use
>> pg_cancel_backend() or set statement_timeout before running this.
>> >
>> > This is valid question - for begin we can use a statement_timeout and
>> we don't need to design some special (if you don't hold some important
>> lock).
>> > My example (the code has prototype quality) is little bit longer, but
>> it work without global lock - the requester doesn't block any other
>>
>> I'll update the commitfest patch to use this technique.
>>
>
> Please find attached v4.
>

It is better

Two notices:

1. The communication mechanism can be used more wide, than only for this
purpose. We can introduce a SendInfoHook - and it can be used for any
customer probes - memory, cpu, ...

2. With your support for explain of nested queries we have all what we need
for integration auto_explain to core.

Regards

Pavel

>
> --
> Alex
>
>