Re: [HACKERS] UPDATE of partition key

On 23 December 2017 at 04:00, Amit Khandekar <amitdkhan(dot)pg(at)gmail(dot)com> wrote:
> On 15 December 2017 at 18:28, Robert Haas <robertmhaas(at)gmail(dot)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.

--
David Rowley http://www.2ndQuadrant.com/
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