Horton

Re: UPDATE of partition key

Amit Kapila <amit.kapila16@gmail.com>

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From: Amit Kapila <amit.kapila16@gmail.com>
To: Amit Khandekar <amitdkhan.pg@gmail.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-06-05T05:57:49Z
Lists: pgsql-hackers 
On Fri, Jun 2, 2017 at 4:37 PM, Amit Khandekar <amitdkhan.pg@gmail.com> wrote:
> On 2 June 2017 at 01:17, Robert Haas <robertmhaas@gmail.com> wrote:
>> On Thu, Jun 1, 2017 at 7:41 AM, Amit Khandekar <amitdkhan.pg@gmail.com> wrote:
>>>> Regarding the trigger issue, I can't claim to have a terribly strong
>>>> opinion on this.  I think that practically anything we do here might
>>>> upset somebody, but probably any halfway-reasonable thing we choose to
>>>> do will be OK for most people.  However, there seems to be a
>>>> discrepancy between the approach that got the most votes and the one
>>>> that is implemented by the v8 patch, so that seems like something to
>>>> fix.
>>>
>>> Yes, I have started working on updating the patch to use that approach
>>> (BR and AR update triggers on source and destination partition
>>> respectively, instead of delete+insert) The approach taken by the
>>> patch (BR update + delete+insert triggers) didn't require any changes
>>> in the way ExecDelete() and ExecInsert() were called. Now we would
>>> require to skip the delete/insert triggers, so some flags need to be
>>> passed to these functions,
>>>

I thought you already need to pass an additional flag for special
handling of ctid in Delete case.  For Insert, a new flag needs to be
passed and need to have a check for that in few places.

> or else have stripped down versions of
>>> ExecDelete() and ExecInsert() which don't do other things like
>>> RETURNING handling and firing triggers.
>>
>> See, that strikes me as a pretty good argument for firing the
>> DELETE+INSERT triggers...
>>
>> I'm not wedded to that approach, but "what makes the code simplest?"
>> is not a bad tiebreak, other things being equal.
>
> Yes, that sounds good to me.
>

I am okay if we want to go ahead with firing BR UPDATE + DELETE +
INSERT triggers for an Update statement (when row movement happens) on
the argument of code simplicity, but it sounds slightly odd behavior.

> But I think we want to wait for other's
> opinion because it is quite understandable that two triggers firing on
> the same partition sounds odd.
>

Yeah, but I think we have to rely on docs in this case as behavior is
not intuitive.

-- 
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com

Commits

  1. Avoid referencing off the end of subplan_partition_offsets.

  2. Allow UPDATE to move rows between partitions.

  3. Remove useless lookup of root partitioned rel in ExecInitModifyTable().

  4. Factor error generation out of ExecPartitionCheck.

  5. Minor preparatory refactoring for UPDATE row movement.

  6. Simplify and encapsulate tuple routing support code.

  7. Avoid coercing a whole-row variable that is already coerced.

  8. Use ResultRelInfo ** rather than ResultRelInfo * for tuple routing.

  9. Make RelationGetPartitionDispatchInfo expand depth-first.

  10. Expand partitioned tables in PartDesc order.

  11. Use a real RT index when setting up partition tuple routing.

  12. Fix transition tables for partition/inheritance.

  13. Fix confusion about number of subplans in partitioned INSERT setup.

  14. Prevent BEFORE triggers from violating partitioning constraints.

  15. Fire per-statement triggers on partitioned tables.

  16. Fix reporting of violations in ExecConstraints, again.

  17. Don't scan partitioned tables.

  18. Allow FDWs to push down quals without breaking EvalPlanQual rechecks.