Horton

Re: UPDATE of partition key

Amit Khandekar <amitdkhan.pg@gmail.com>

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From: Amit Khandekar <amitdkhan.pg@gmail.com>
To: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
Cc: Etsuro Fujita <fujita.etsuro@lab.ntt.co.jp>, Robert Haas <robertmhaas@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Dilip Kumar <dilipbalaut@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>
Date: 2017-07-04T09:53:05Z
Lists: pgsql-hackers 
On 4 July 2017 at 14:48, Amit Khandekar <amitdkhan.pg@gmail.com> wrote:
> On 4 July 2017 at 14:38, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp> wrote:
>> On 2017/07/04 17:25, Etsuro Fujita wrote:
>>> On 2017/07/03 18:54, Amit Langote wrote:
>>>> On 2017/07/02 20:10, Robert Haas wrote:
>>>>> That
>>>>> seems pretty easy to do - just have expand_inherited_rtentry() notice
>>>>> that it's got a partitioned table and call
>>>>> RelationGetPartitionDispatchInfo() instead of find_all_inheritors() to
>>>>> produce the list of OIDs.
>>> Seems like a good idea.
>>>
>>>> Interesting idea.
>>>>
>>>> If we are going to do this, I think we may need to modify
>>>> RelationGetPartitionDispatchInfo() a bit or invent an alternative that
>>>> does not do as much work.  Currently, it assumes that it's only ever
>>>> called by ExecSetupPartitionTupleRouting() and hence also generates
>>>> PartitionDispatchInfo objects for partitioned child tables.  We don't need
>>>> that if called from within the planner.
>>>>
>>>> Actually, it seems that RelationGetPartitionDispatchInfo() is too coupled
>>>> with its usage within the executor, because there is this comment:
>>>>
>>>>          /*
>>>>           * We keep the partitioned ones open until we're done using the
>>>>           * information being collected here (for example, see
>>>>           * ExecEndModifyTable).
>>>>           */
>>>
>>> Yeah, we need some refactoring work.  Is anyone working on that?
>>
>> I would like to take a shot at that if someone else hasn't already cooked
>> up a patch.  Working on making RelationGetPartitionDispatchInfo() a
>> routine callable from both within the planner and the executor should be a
>> worthwhile effort.
>
> What I am currently working on is to see if we can call
> find_all_inheritors() or find_inheritance_children() instead of
> generating the leaf_part_oids using APPEND_REL_PARTITION_OIDS().
> Possibly we don't have to refactor it completely.
> find_inheritance_children() needs to return the oids in canonical
> order. So in find_inheritance_children () need to re-use part of
> RelationBuildPartitionDesc() where it generates those oids in that
> order. I am checking this part, and am going to come up with an
> approach based on findings.

The other approach is to make canonical ordering only in
find_all_inheritors() by replacing call to find_inheritance_children()
with the refactored/modified RelationGetPartitionDispatchInfo(). But
that would mean that the callers of find_inheritance_children() would
have one ordering, while the callers of find_all_inheritors() would
have a different ordering; that brings up chances of deadlocks. That's
why I think, we need to think about modifying the common function
find_inheritance_children(), so that we would be consistent with the
ordering. And then use find_inheritance_children() or
find_all_inheritors() in RelationGetPartitionDispatchInfo(). So yes,
there would be some modifications to
RelationGetPartitionDispatchInfo().

>
> Also, need to investigate whether *always* sorting the oids in
> canonical order is going to be much expensive than the current sorting
> using oids. But I guess it won't be that expensive.
>
>
> --
> Thanks,
> -Amit Khandekar
> EnterpriseDB Corporation
> The Postgres Database Company



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

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.