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Re: postgres_fdw: wrong results with self join + enable_nestloop off

Etsuro Fujita <etsuro.fujita@gmail.com>

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From: Etsuro Fujita <etsuro.fujita@gmail.com>
To: Richard Guo <guofenglinux@gmail.com>
Cc: Nishant Sharma <nishant.sharma@enterprisedb.com>, Suraj Kharage <suraj.kharage@enterprisedb.com>, pgsql-hackers@postgresql.org
Date: 2023-07-28T08:55:52Z
Lists: pgsql-hackers

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Hi Richard,

On Mon, Jul 24, 2023 at 11:45 AM Richard Guo <guofenglinux@gmail.com> wrote:
> On Fri, Jul 21, 2023 at 8:51 PM Etsuro Fujita <etsuro.fujita@gmail.com> wrote:
>> * In this bit I changed the last argument to NIL, which would be
>> nitpicking, though.
>>
>> @@ -1038,7 +1038,7 @@ postgresGetForeignPaths(PlannerInfo *root,
>>   add_path(baserel, (Path *) path);
>>
>>   /* Add paths with pathkeys */
>> - add_paths_with_pathkeys_for_rel(root, baserel, NULL);
>> + add_paths_with_pathkeys_for_rel(root, baserel, NULL, NULL);

> This was my oversight.

No.  IIUC, I think that that would work well as-proposed, but I
changed it as such, for readability.

> So the two patches both look good to me now.

Cool!  I pushed the first patch after polishing it a little bit, so
here is a rebased version of the second patch, in which I modified the
ForeignPath and CustomPath cases in reparameterize_path_by_child() to
reflect the new members fdw_restrictinfo and custom_restrictinfo, for
safety, and tweaked a comment a bit.

Thanks for looking!

Best regards,
Etsuro Fujita

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Re-allow FDWs and custom scan providers to replace joins with pseudoconstant quals.

  2. Disallow replacing joins with scans in problematic cases.

  3. doc: PQinitOpenSSL and PQinitSSL are obsolete in OpenSSL 1.1.0+