Horton

Re: BUG #19102: Assertion failure in generate_orderedappend_paths with aggregate pushdown

Richard Guo <guofenglinux@gmail.com>

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From: Richard Guo <guofenglinux@gmail.com>
To: Kuntal Ghosh <kuntalghosh.2007@gmail.com>
Cc: pgsql-bugs@lists.postgresql.org, akorotkov@postgresql.org
Date: 2025-11-03T10:09:25Z
Lists: pgsql-bugs

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  1. Fix assertion failure in generate_orderedappend_paths()

  2. Avoid creating duplicate ordered append paths

On Mon, Nov 3, 2025 at 2:58 PM Kuntal Ghosh <kuntalghosh.2007@gmail.com> wrote:
> On Mon, Nov 3, 2025 at 11:22 AM PG Bug reporting form <noreply@postgresql.org> wrote:
>> Server crashes with assertion failure:
>> TRAP: FailedAssertion("childrel->rows > 0", File: "allpaths.c", Line: 1983)
>>
>> To fix the issue, we can replace the direct division with
>> clamp_row_est(childrel->rows) to safely handle zero, and remove the
>> incorrect assertion:
>>
>> -   Assert(childrel->rows > 0);
>> -   path_fraction /= childrel->rows;
>> +   path_fraction /= clamp_row_est(childrel->rows);
>>
> Added a patch with the proposed fix and regression test.

Thanks for the report -- that's a good catch.  However, I don't think
we should use childrel->rows to calculate the fraction in the first
place.  It would be better to use cheapest_total->rows instead.

- Richard