Re: UPDATE of partition key

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.

Regards,
Amul