Re: Defer selection of asynchronous subplans until the executor initialization stage - Mailing list pgsql-hackers

From Zhihong Yu
Subject Re: Defer selection of asynchronous subplans until the executor initialization stage
Date
Msg-id CALNJ-vRF1fw9dh-2sZW9bETqwcttOMw4ptLp6sOrzVUSw=Ycvw@mail.gmail.com
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In response to Re: Defer selection of asynchronous subplans until the executor initialization stage  (Andrey Lepikhov <a.lepikhov@postgrespro.ru>)
Responses Re: Defer selection of asynchronous subplans until the executor initialization stage  (Justin Pryzby <pryzby@telsasoft.com>)
List pgsql-hackers


On Sun, Apr 10, 2022 at 3:42 AM Etsuro Fujita <etsuro.fujita@gmail.com> wrote:
On Sat, Apr 9, 2022 at 1:58 AM Etsuro Fujita <etsuro.fujita@gmail.com> wrote:
> On Fri, Apr 8, 2022 at 9:43 PM 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.
>
> Reproduced.  Will look into this.

I think the cause of this is that mark_async_capable_plan() failed to
take into account that when the given path is a SubqueryScanPath or
ForeignPath, the given corresponding plan might include a gating
Result node that evaluates pseudoconstant quals.  My oversight.  :-(
Attached is a patch for fixing that.  I think v14 has the same issue,
so I think we need backpatching.

Best regards,
Etsuro Fujita
Hi,
Looking at the second hunk of the patch:
                FdwRoutine *fdwroutine = path->parent->fdwroutine; 
...
+               if (IsA(plan, Result))
+                   return false;

It seems the check of whether plan is a Result node can be lifted ahead of the switch statement (i.e. to the beginning of mark_async_capable_plan).

This way, we don't have to check for every case in the switch statement.

Cheers

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