Horton

Re: [HACKERS] UPDATE of partition key

Amit Khandekar <amitdkhan.pg@gmail.com>

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From: Amit Khandekar <amitdkhan.pg@gmail.com>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: Robert Haas <robertmhaas@gmail.com>, Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>, pgsql-hackers <pgsql-hackers@postgresql.org>, Thomas Munro <thomas.munro@enterprisedb.com>
Date: 2018-01-03T06:12:50Z
Lists: pgsql-hackers 
On 2 January 2018 at 10:56, David Rowley <david.rowley@2ndquadrant.com> wrote:
> On 23 December 2017 at 04:00, Amit Khandekar <amitdkhan.pg@gmail.com> wrote:
>> On 15 December 2017 at 18:28, Robert Haas <robertmhaas@gmail.com> wrote:
>>> -    PartitionDispatch **pd,
>>> -    ResultRelInfo ***partitions,
>>> -    TupleConversionMap ***tup_conv_maps,
>>> -    TupleTableSlot **partition_tuple_slot,
>>> -    int *num_parted, int *num_partitions)
>>> +    PartitionTupleRouting **partition_tuple_routing)
>>>
>>> Since we're consolidating all of ExecSetupPartitionTupleRouting's
>>> output parameters into a single structure, I think it might make more
>>> sense to have it just return that value.  I think it's only done with
>>> output parameter today because there are so many different things
>>> being produced, and we can't return them all.
>>
>> You mean ExecSetupPartitionTupleRouting() will return the structure
>> (not pointer to structure), and the caller will get the copy of the
>> structure like this ? :
>>
>> mtstate->mt_partition_tuple_routing =
>> ExecSetupPartitionTupleRouting(mtstate, rel, node->nominalRelation, estate);
>>
>> I am ok with that, but just wanted to confirm if that is what you are
>> saying. I don't recall seeing a structure return value in PG code, so
>> not sure if it is conventional in PG to do that. Hence, I am somewhat
>> inclined to keep it as output param. It also avoids a structure copy.
>>
>> Another way is for ExecSetupPartitionTupleRouting() to palloc this
>> structure, and return its pointer, but then caller would have to
>> anyway do a structure copy, so that's not convenient, and I don't
>> think you are suggesting this way either.
>
> I'm pretty sure Robert is suggesting that
> ExecSetupPartitionTupleRouting pallocs the memory for the structure,
> sets it up then returns a pointer to the new struct. That's not very
> unusual. It seems unusual for a function to return void and modify a
> single parameter pointer to get the value to the caller rather than
> just to return that value.

Sorry, my mistake. Earlier I somehow was under the impression that the
callers of ExecSetupPartitionTupleRouting() already have this
structure palloc'ed, and that they pass address of this structure. I
now can see that both CopyStateData->partition_tuple_routing and
ModifyTableState->mt_partition_tuple_routing are pointers, not
structures. So it make perfect sense for
ExecSetupPartitionTupleRouting() to palloc and return a pointer. Sorry
for the noise. Will share the change in an upcoming patch version.
Thanks !

-- 
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.