Re: BUG #19405: Assertion in eval_windowaggregates() fails due to integer overflow

Richard Guo <guofenglinux@gmail.com> 于2026年2月14日周六 17:41写道：
>
> On Fri, Feb 13, 2026 at 7:09 PM PG Bug reporting form
> <noreply@postgresql.org> wrote:
> > The following script:
> > CREATE TABLE t (i integer);
> > INSERT INTO t SELECT g FROM generate_series(1, 2) g;
> > SELECT SUM(i) OVER (ROWS BETWEEN 1 PRECEDING AND 0x7fffffffffffffff
> > FOLLOWING EXCLUDE CURRENT ROW) FROM t;
>
> Thanks for the report.  Reproduced here.
>
> It seems to be caused by a signed integer overflow in row_is_in_frame
> when calculating the frame's end position:
>
>             if (pos > winstate->currentpos + offset)
>                 return -1;
>
> When offset is very large (close to INT64_MAX, as in the reported
> case), the addition can overflow, in which case the result would wrap
> to a negative number (with -fwrapv), causing the comparison to
> incorrectly return true.  In release builds, this causes valid rows to
> be excluded from the window frame.  In debug builds, it leads to an
> assertion failure.

Yes, the code above may overflow; in debug builds, the assertion would fail.

>
> I think we can fix this by leveraging the overflow-aware integer
> operation (ie, pg_add_s64_overflow) to perform the addition here.  If
> an overflow is detected, we can assume the frame boundary extends to
> the end of the partition, meaning the current row is within the frame.
>
I've also considered similar solutions.  But I'm not very familiar
with the window function
internal codes, so not sure it's the right fix.


> Right, I noticed this one too.  Basically, nodeWindowAgg.c doesn't
> check for overflow when adding startOffsetValue or endOffsetValue.
> Since these values are provided by the user and can be arbitrarily
> large, simple addition does not seem safe.  I think we may need to
> switch to overflow-aware integer operations in all relevant code.

>Here is an updated patch to fix all relevant code in nodeWindowAgg.c.

v2 seems to cover all cases. WFM.

In window.sql, we don't have a test case for this issue. I think we
should add it to the window.sql

-- 
Thanks,
Tender Wang