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help / color / mirror / Atom feedFrom: Etsuro Fujita <[email protected]>
To: Amit Langote <[email protected]>
Cc: Richard Guo <[email protected]>
Cc: Matheus Alcantara <[email protected]>
Cc: Ayush Tiwari <[email protected]>
Cc: Rafia Sabih <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Amit Langote <[email protected]>
Subject: Re: BUG #19484: Segmentation fault triggered by FDW
Date: Thu, 25 Jun 2026 02:02:41 +0900
Message-ID: <CAPmGK15do2D1YJFR2VST6+8BnADyZbiiY1hk+HhMGgFyBkE70Q@mail.gmail.com> (raw)
In-Reply-To: <CA+HiwqFd61sXgUWijKg8DfRQDtwYEGSdxuEPDb8rq22rxzxN_g@mail.gmail.com>
References: <[email protected]>
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Amit-san,
On Wed, Jun 24, 2026 at 8:20 PM Amit Langote <[email protected]> wrote:
> On Wed, Jun 24, 2026 at 6:15 PM Etsuro Fujita <[email protected]> wrote:
> > + /*
> > + * node->fdwPrivLists is indexed by the original, pre-pruning
> > + * result relation order and is parallel to node->resultRelations.
> > + * Initial pruning may have dropped earlier relations, so the kept
> > + * index j need not match the original position; find this
> > + * relation's entry by its range table index instead.
> > + */
> > + forboth(lc1, node->resultRelations, lc2, node->fdwPrivLists)
> > + {
> > + if (lfirst_int(lc1) == (int) rti)
> > + {
> > + fdw_private = (List *) lfirst(lc2);
> > + break;
> > + }
> > + }
> >
> > I think it's good to skip this for efficiency, when there are no
> > pruned result relations.
>
> Thanks for the review. v2 attached implements your suggestion: it
> indexes node->fdwPrivLists directly with j when no result relations
> were pruned, and only falls back to matching by range table index when
> pruning appears to have dropped some.
Thank you for doing that work!
This might be nitpicking, but:
+ if (list_length(node->resultRelations) == mtstate->mt_nrels)
+ fdw_private = (List *) list_nth(node->fdwPrivLists, j);
+ else
+ {
+ Index rti = resultRelInfo->ri_RangeTableIndex;
+ ListCell *lc1;
+ ListCell *lc2;
+
+ fdw_private = NIL;
+ forboth(lc1, node->resultRelations, lc2, node->fdwPrivLists)
+ {
+ if (lfirst_int(lc1) == (int) rti)
+ {
+ fdw_private = (List *) lfirst(lc2);
+ break;
+ }
+ }
+ }
I'd put the if-test outside of the outer loop to save cycles.
Other than that v2 looks good to me.
(The forboth loop actually causes an n-squared calculation, but it's
done only when pruning occurs, in which case the number of remaining
result relations would be reduced, so that wouldn't be a problem.)
Best regards,
Etsuro Fujita
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Subject: Re: BUG #19484: Segmentation fault triggered by FDW
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