Re: BUG #16369: Segmentation Faults and Data Corruption with Generated Columns

On 2020-04-16 07:30, Michael Paquier wrote:
> On Thu, Apr 16, 2020 at 12:40:24PM +1200, David Rowley wrote:
>> On Thu, 16 Apr 2020 at 11:52, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>>> That looks like it'll fail on a null result.
>>
>> Thanks. I'll have another go then.
>
> Shouldn't you have more regression test cases here? I guess one for
> the non-NULL case, and one for the NULL case?

I've tried creating a smaller test case, but it's difficult. I haven't
fully understood the reason why it sometimes crashes and sometimes not.
The smallest I could come up with so far is something like this:

CREATE TABLE crash (
hostname varchar,
hostname_short varchar GENERATED ALWAYS AS (hostname) STORED,
device text,
mount text,
used_space_bytes bigint,
avail_space_bytes bigint
);
INSERT INTO crash (hostname, device, mount, used_space_bytes,
avail_space_bytes) VALUES (repeat('1234567890', 100), 'devtmpfs',
'/dev', 0, 6047076131313);

Would this be easier to reproduce with one of the memory-cleaning
#defines enabled?

--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services