Re: UPDATE of partition key

On Wed, Sep 13, 2017 at 4:24 PM, amul sul <sulamul(at)gmail(dot)com> wrote:
>
>
> On Sun, Sep 10, 2017 at 8:47 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
> wrote:
>>
>> On Fri, Sep 8, 2017 at 4:51 PM, amul sul <sulamul(at)gmail(dot)com> wrote:
>> > On Thu, May 18, 2017 at 9:13 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
>> > wrote:
>> >>
>> >> On Wed, May 17, 2017 at 5:17 PM, Robert Haas <robertmhaas(at)gmail(dot)com>
>> >> wrote:
>> >> > On Wed, May 17, 2017 at 6:29 AM, Amit Kapila
>> >> > <amit(dot)kapila16(at)gmail(dot)com>
>> >> > wrote:
>> >> >> I think we can do this even without using an additional infomask
>> >> >> bit.
>> >> >> As suggested by Greg up thread, we can set InvalidBlockId in ctid to
>> >> >> indicate such an update.
>> >> >
>> >> > Hmm. How would that work?
>> >> >
>> >>
>> >> We can pass a flag say row_moved (or require_row_movement) to
>> >> heap_delete which will in turn set InvalidBlockId in ctid instead of
>> >> setting it to self. Then the ExecUpdate needs to check for the same
>> >> and return an error when heap_update is not successful (result !=
>> >> HeapTupleMayBeUpdated). Can you explain what difficulty are you
>> >> envisioning?
>> >>
>> >
>> > Attaching WIP patch incorporates the above logic, although I am yet to
>> > check
>> > all the code for places which might be using ip_blkid. I have got a
>> > small
>> > query here,
>> > do we need an error on HeapTupleSelfUpdated case as well?
>> >
>>
>> No, because that case is anyway a no-op (or error depending on whether
>> is updated/deleted by same command or later command). Basically, even
>> if the row wouldn't have been moved to another partition, we would not
>> have allowed the command to proceed with the update. This handling is
>> to make commands fail rather than a no-op where otherwise (when the
>> tuple is not moved to another partition) the command would have
>> succeeded.
>>
> Thank you.
>
> I've rebased patch against Amit Khandekar's latest patch (v17_rebased_2).
> Also, added ip_blkid validation check in heap_get_latest_tid(), rewrite_heap_tuple()
> & rewrite_heap_tuple() function, because only ItemPointerEquals() check is no
> longer sufficient after this patch.

FYI, I have posted this patch in a separate thread :
https://postgr.es/m/CAAJ_b95PkwojoYfz0bzXU8OokcTVGzN6vYGCNVUukeUDrnF3dw@mail.gmail.com

Regards,
Amul