Re: expanding inheritance in partition bound order

On 18 August 2017 at 10:55, Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp> wrote:
> On 2017/08/18 4:54, Robert Haas wrote:
>> On Thu, Aug 17, 2017 at 8:39 AM, Ashutosh Bapat
>> <ashutosh(dot)bapat(at)enterprisedb(dot)com> wrote:
>>> [2] had a patch with some changes to the original patch you posted. I
>>> didn't describe those changes in my mail, since they rearranged the
>>> comments. Those changes are not part of this patch and you haven't
>>> comments about those changes as well. If you have intentionally
>>> excluded those changes, it's fine. In case, you haven't reviewed them,
>>> please see if they are good to be incorporated.
>>
>> I took a quick look at your version but I think I like Amit's fine the
>> way it is, so committed that and back-patched it to v10.
>
> Thanks for committing.
>
>> I find 0002 pretty ugly as things stand. We get a bunch of tuple maps
>> that we don't really need, only to turn around and free them. We get
>> a bunch of tuple slots that we don't need, only to turn around and
>> drop them. We don't really need the PartitionDispatch objects either,
>> except for the OIDs they contain. There's a lot of extra stuff being
>> computed here that is really irrelevant for this purpose. I think we
>> should try to clean that up somehow.
>
> One way to do that might be to reverse the order of the remaining patches
> and put the patch to refactor RelationGetPartitionDispatchInfo() first.
> With that refactoring, PartitionDispatch itself has become much simpler in
> that it does not contain a relcache reference to be closed eventually by
> the caller, the tuple map, and the tuple table slot. Since those things
> are required for tuple-routing, the refactoring makes
> ExecSetupPartitionTupleRouting itself create them from the (minimal)
> information returned by RelationGetPartitionDispatchInfo and ultimately
> destroy when done using it. I kept the indexes field in
> PartitionDispatchData though, because it's essentially free to create
> while we are walking the partition tree in
> RelationGetPartitionDispatchInfo() and it seems undesirable to make the
> caller compute that information (indexes) by traversing the partition tree
> all over again, if it doesn't otherwise have to. I am still considering
> some counter-arguments raised by Amit Khandekar about this last assertion.
>
> Thoughts?

One another approach (that I have used in update-partition-key patch)
is to *not* generate the oids beforehand, and instead, call a
partition_walker_next() function to traverse through the tree. Each
next() function would return a ChildInfo that includes child oid,
parent oid, etc. All users of this would guarantee a fixed order of
oids. In the update-partition-key patch, I am opening and closing each
of the children, which of course, we need to avoid.

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