Re: backend crash

On Mon, Apr 13, 2020 at 06:02:34PM +0200, Kamil Jońca wrote:
>Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
>
>> On Mon, Apr 13, 2020 at 11:01:01AM -0400, Tom Lane wrote:
>>>Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
>>>> On Mon, Apr 13, 2020 at 09:25:35AM +0200, Kamil Jońca wrote:
>>>>> I have problem with (pseudo) random backend crashes.
>>>>> They seems to happen at one query, but not every time.
>>>
>>>> I've tried to reproduce this, but unfortunately it does not fail for me.
>>>> Chances are this depends on data. Can you prepare a small data sample
>>>> that would trigger the issue?
>>>
>>>This is evidently a parallel-query worker, so it's unlikely you'd ever
>>>get anywhere near this crash with a "small" data sample; for starters
>>>there'd have to be enough data to prompt use of a parallel plan.
>>>
>>>I doubt that the crash is very data-specific though.  Maybe just fill
>>>the table with a lot of dummy data?
>>>
>>
>> I did that, of course, and the plan looks like this:
>>
>
>1. Did you try run this many times? As I wrote this does not crash every
>time. I can reproduce this on my data by running query 1000 times in
>loop.

I did run it about 100x, I'll reduce the amount of data and let it run.

How often it crashes? What execution plan does it use?

>2. I can try to prepare test data, but it will be rather long
>process. Stay tuned :/

OK

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services