Re: [HACKERS] Restrict concurrent update/delete with UPDATE of partition key

On Sat, Nov 11, 2017 at 1:05 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Wed, Sep 27, 2017 at 7:07 AM, amul sul <sulamul(at)gmail(dot)com> wrote:
>> Attaching POC patch that throws an error in the case of a concurrent update
>> to an already deleted tuple due to UPDATE of partition key[1].
>>
>> In a normal update new tuple is linked to the old one via ctid forming
>> a chain of tuple versions but UPDATE of partition key[1] move tuple
>> from one partition to an another partition table which breaks that chain.
>
> This patch needs a rebase. It has one whitespace-only hunk that
> should possibly be excluded.
>
Thanks for looking at the patch.

> I think the basic idea of this is sound. Either you or Amit need to
> document the behavior in the user-facing documentation, and it needs
> tests that hit every single one of the new error checks you've added
> (obviously, the tests will only work in combination with Amit's
> patch). The isolation should be sufficient to write such tests.
>
> It needs some more extensive comments as well. The fact that we're
> assigning a meaning to ip_blkid -> InvalidBlockNumber is a big deal,
> and should at least be documented in itemptr.h in the comments for the
> ItemPointerData structure.
>
> I suspect ExecOnConflictUpdate needs an update for the
> HeapTupleUpdated case similar to what you've done elsewhere.
>

UPDATE of partition key v25[1] has documented this concurrent scenario,
I need to rework on that document paragraph to include this behaviour, will
discuss with Amit.

Attached 0001 patch includes error check for 8 functions, out of 8 I am able
to build isolation test for 4 functions -- ExecUpdate,ExecDelete,
GetTupleForTrigger & ExecLockRows.

And remaining are EvalPlanQualFetch, ExecOnConflictUpdate,
RelationFindReplTupleByIndex & RelationFindReplTupleSeq. Note that check in
RelationFindReplTupleByIndex & RelationFindReplTupleSeq will have LOG not an
ERROR.

Any help/suggestion to build test for these function would be much appreciated.

1] http://postgr.es/m/CAJ3gD9f4Um99sOJmVSEPj783VWw5GbXkgU3OWcYZJv=ipjTkAw@mail.gmail.com

Regards,
Amul