Re: UPDATE of partition key

On 18 May 2017 at 16:52, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Wed, May 17, 2017 at 4:05 PM, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
>> On Wed, May 17, 2017 at 3:15 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
>>>> Earlier I thought that option1 is better but later I think that this
>>>> can complicate the situation as we are firing first BR update then BR
>>>> delete and can change the row multiple time and defining such
>>>> behaviour can be complicated.
>>>>
>>>
>>> If we have to go by this theory, then the option you have preferred
>>> will still execute BR triggers for both delete and insert, so input
>>> row can still be changed twice.
>>
>> Yeah, right as per my theory above Option3 have the same problem.
>>
>> But after putting some more thought I realised that only for "Before
>> Update" or the "Before Insert" trigger row can be changed.
>>
>
> Before Row Delete triggers can suppress the delete operation itself
> which is kind of unintended in this case. I think without the user
> being aware it doesn't seem advisable to execute multiple BR triggers.

By now, majority of the opinions have shown that they do not favour
two triggers getting fired on a single update. Amit, do you consider
option 2 as a valid option ? That is, fire only UPDATE triggers. BR on
source partition, and AR on destination partition. Do you agree that
firing BR update trigger is essential since it can modify the row and
even prevent the update from happening ?

Also, since a user does not have a provision to install a common
UPDATE row trigger, (s)he installs it on each of the leaf partitions.
And then when an update causes row movement, using option 3 would end
up not firing update triggers on any of the partitions. So, I prefer
option 2 over option 3 , i.e. make sure to fire BR and AR update
triggers. Actually option 2 is what Robert had proposed in the
beginning.

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