Re: partition tree inspection functions

On Tue, Oct 09, 2018 at 06:41:59PM +0900, Amit Langote wrote:
> 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.

I have to admit that I find the concept non-intuitive.  A partition tree
is a set of partitions based on a root called a partitioned table.  A
partitioned index is not a partition, it is a specific object which is
associated to a partitioned table without any physical on-disk presence.
An index is not a partition as well, it is an object associated to one
relation.

I am not saying that there is no merit in that.  I honestly don't know,
but being able to list all the partitioned tables and their partition
tables looks enough to cover all the grounds discussed, and there is no
need to work out more details for a new clone of find_all_inheritors and
get_partition_ancestors.
--
Michael