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

On Wed, Sep 2, 2015 at 3:07 PM, Shulgin, Oleksandr <
oleksandr(dot)shulgin(at)zalando(dot)de> wrote:

> On Wed, Sep 2, 2015 at 3:04 PM, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> wrote:
>>
>>
>>> Well, maybe I'm missing something, but sh_mq_create() will just
>>> overwrite the contents of the struct, so it doesn't care about
>>> sender/receiver: only sh_mq_set_sender/receiver() do.
>>>
>>
>> if you create sh_mq from scratch, then you can reuse structure.
>>
>
Please find attached a v3.

It uses a shared memory queue and also has the ability to capture plans
nested deeply in the call stack. Not sure about using the executor hook,
since this is not an extension...

The LWLock is used around initializing/cleaning the shared struct and the
message queue, the IO synchronization is handled by the message queue
itself. After some testing with concurrent pgbench and intentionally deep
recursive plpgsql functions (up to 700 plpgsql stack frames) I think this
approach can work. Unless there's some theoretical problem I'm just not
aware of. :-)

Comments welcome!
--
Alex