Horton

Re: Defer selection of asynchronous subplans until the executor initialization stage

Etsuro Fujita <etsuro.fujita@gmail.com>

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From: Etsuro Fujita <etsuro.fujita@gmail.com>
To: Zhihong Yu <zyu@yugabyte.com>
Cc: Justin Pryzby <pryzby@telsasoft.com>, Alexander Pyhalov <a.pyhalov@postgrespro.ru>, "Andrey V. Lepikhov" <a.lepikhov@postgrespro.ru>, Kyotaro Horiguchi <horikyota.ntt@gmail.com>, PostgreSQL Developers <pgsql-hackers@lists.postgresql.org>
Date: 2022-04-10T10:58:30Z
Lists: pgsql-hackers 
Hi,

On Sat, Apr 9, 2022 at 1:24 AM Zhihong Yu <zyu@yugabyte.com> wrote:
> On Fri, Apr 8, 2022 at 5:43 AM Justin Pryzby <pryzby@telsasoft.com> wrote:
>> This patch seems to be causing the planner to crash.
>> Here's a query reduced from sqlsmith.
>>
>> | explain SELECT 1 FROM information_schema.constraint_column_usage WHERE 1 <= pg_trigger_depth();
>>
>> Program terminated with signal SIGSEGV, Segmentation fault.

> I logged the value of plan->scanstatus before the assertion :
>
> 2022-04-08 16:20:59.601 UTC [26325] LOG:  scan status 0
> 2022-04-08 16:20:59.601 UTC [26325] STATEMENT:  explain SELECT 1 FROM information_schema.constraint_column_usage WHERE 1 <= pg_trigger_depth();
> 2022-04-08 16:20:59.796 UTC [26296] LOG:  server process (PID 26325) was terminated by signal 11: Segmentation fault
>
> It seems its value was SUBQUERY_SCAN_UNKNOWN.
>
> Still trying to find out the cause for the crash.

I think the cause is an oversight in mark_async_capable_plan().  See [1].

Thanks!

Best regards,
Etsuro Fujita

[1] https://www.postgresql.org/message-id/CAPmGK15NkuaVo0Fu_0TfoCpPPJaJi4OMLzEQtkE6Bt6YT52fPQ%40mail.gmail.com

Commits

  1. Improve comments for trivial_subqueryscan().

  2. Disable asynchronous execution if using gating Result nodes.

  3. Allow asynchronous execution in more cases.

  4. Doc: Further update documentation for asynchronous execution.

  5. Fix rescanning of async-aware Append nodes.

  6. Doc: Update documentation for asynchronous execution.

  7. Fix EXPLAIN ANALYZE for async-capable nodes.

  8. Minor code cleanup in asynchronous execution support.

  9. Adjust input value to WaitEventSetWait() in ExecAppendAsyncEventWait().

  10. Add support for asynchronous execution.