Re: [HACKERS] UPDATE of partition key

On 22 January 2018 at 02:40, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Sun, Jan 21, 2018 at 1:43 AM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>>> Committed with a bunch of mostly-cosmetic revisions.
>>
>> Buildfarm member skink has been unhappy since this patch went in.
>> Running the regression tests under valgrind easily reproduces the
>> failure. Now, I might be wrong about which of the patches committed
>> on Friday caused the unhappiness, but the valgrind backtrace sure
>> looks like it's to do with partition routing:
>
> Yeah, that must be the fault of this patch. We assign to
> proute->subplan_partition_offsets[update_rri_index] from
> update_rri_index = 0 .. num_update_rri, and there's an Assert() at the
> bottom of this function that checks this, so probably this is indexing
> off the end of the array. I bet the issue happens when we find all of
> the UPDATE result rels while there are still partitions left; then,
> subplan_index will be equal to the length of the
> proute->subplan_partition_offsets array and we'll be indexing just off
> the end.

Yes, right, that's what is happening. It is not happening on an Assert
though (there is no assert in that function). It is happening when we
try to access the array here :

if (proute->subplan_partition_offsets &&
proute->subplan_partition_offsets[subplan_index] == i)

Attached is a fix, where I have introduced another field
PartitionTupleRouting.num_ subplan_partition_offsets, so that above,
we can add another condition (subplan_index <
proute->num_subplan_partition_offsets) in order to stop accessing the
array once we are done with all the offset array elements.

Ran the update.sql test with valgrind enabled on my laptop, and the
valgrind output now does not show errors.

--
Thanks,
-Amit Khandekar
EnterpriseDB Corporation
The Postgres Database Company