Re: partition tree inspection functions

On 2018/10/09 18:10, Michael Paquier wrote:
> On Tue, Oct 09, 2018 at 05:11:59PM +0900, Amit Langote wrote:
>> Hmm, how would one find the size of a partitioned index tree if we don't
>> allow indexes to be passed?
>
> pg_total_relation_size() and pg_indexes_size() are designed for that
> purpose. Anyway, the elements of a partition tree are things which can
> be directly attached to it, like a table or a foreign table, and not
> objects which are directly dependent on a given table, like indexes or
> toast tables. So we have to add some filtering on the relkind.
> Indexes, partitioned indexes and sequences are three things which cannot
> be added as partitions. But I think that we had better just make sure
> that the filtering allows RELKIND_RELATION, RELKIND_PARTITIONED_TABLE
> and RELKIND_FOREIGN_TABLE relations only.

I think the way I phrased my question may have been a bit confusing. I
was pointing out that just like tables, indexes can now also form their
own partition tree.

Partitioned indexes, just like partitioned tables, don't have their own
storage, so pg_relation_size() cannot be used to obtain their size. We
decided that the correct way to get the partitioned table's size is *not*
to modify pg_relation_size itself to internally find all partitions and
sum their sizes, but to provide a function that returns partitions and
tell users to write SQL queries around it to calculate the total size.
I'm saying that the new function should be able to be used with
partitioned indexes too.

Thanks,
Amit