> That very much depends on where exactly the failure happens - it might
> be both (or relying on an assumption that changed over). It's not clear
> if it fails during query execution or formatting the output (I seem to
> remember there were/are issues with rows containing multiple large bytea
> values, for example).
>
> Can you attach gdb to the backend, set breakpoint on that elog and share
> the backtrace? Then we can investigate further.
I can't easily get a meaningful query plan (i.e. from the live system)
as the query that failed is based on a temporary table built by some
pl/pgsql (the database is more of a conveyor belt than a long term store).
Unfortunately it's difficult to reproduce the ERROR. This has only
occurred a couple of times on a live system in the last year and these
queries run frequently.
I think we will move to 9.5.10 and see if it ever happens again; then if
it does get a backtrace on that newer version. Incidentally we never saw
this error on 8.4 where this code was running from 2009 until 2017.
> I'll bet you it's not that. It's quite unlikely that would fail with
> exactly 1GB request size. It seems much more like a buffer that we keep
> to be power of 2. The question is which one.
I had dismissed corruption before writing in. It's exactly 1GB every
time this has happened - and we can dump the full dataset periodically
without issue.
>> I have my money on a corrupted TOAST entry. Is this happening on
>> trustworthy hardware or beige box with no ECC or RAID?
It's good quality commercial hardware in our colo - no exactly sure what.
Thanks for taking the time to look at this!
Stefan
On 01/30/18 22:00, Tomas Vondra wrote:
>
>
> On 01/30/2018 10:43 PM, Jan Wieck wrote:
>>
>>
>> On Tue, Jan 30, 2018 at 12:35 PM, Stefan Blanke
>> <stefan.blanke@framestore.com <mailto:stefan.blanke@framestore.com>> wrote:
>>
>> Hello,
>>
>> We've tripped over an error when doing a "COPY.. TO STDOUT WITH
>> BINARY" query.
>>
>> "ERROR: invalid memory alloc request size 1073741824"
>> (exactly 1GB)
>>
>>
>> I have my money on a corrupted TOAST entry. Is this happening on
>> trustworthy hardware or beige box with no ECC or RAID?
>>
>
> I'll bet you it's not that. It's quite unlikely that would fail with
> exactly 1GB request size. It seems much more like a buffer that we keep
> to be power of 2. The question is which one.
>
>
> regards
>
