Re: [HACKERS] UPDATE of partition key

On Fri, Sep 8, 2017 at 4:51 PM, amul sul <sulamul@gmail.com> wrote:
> On Thu, May 18, 2017 at 9:13 AM, Amit Kapila <amit.kapila16@gmail.com>
> wrote:
>>
>>  On Wed, May 17, 2017 at 5:17 PM, Robert Haas <robertmhaas@gmail.com>
>> wrote:
>> > On Wed, May 17, 2017 at 6:29 AM, Amit Kapila <amit.kapila16@gmail.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.