Re: pg_(total_)relation_size and partitioned tables

On 12/18/17 00:17, Amit Langote wrote:
> I agree with the Robert's point which both David and Michael seem to agree
> with that we shouldn't really be changing what pg_relation_size() is doing
> under the covers. And I guess the same for pg_table_size(), too. Both of
> those functions and their siblings work with relations that possess
> on-disk structures and have associated relations (TOAST, indexes) that in
> turn possess on-disk structures. It seems quite clearly documented as
> such. Partitioned tables are different in that they neither possess
> on-disk structures nor have any relations (TOAST, indexes) associated
> directly with them. Instead, they have partitions that are the relations
> that aforementioned dbsize.c functions are familiar with.

Here is another idea. If we had a function

pg_partition_root(regclass) returns regclass

(returning itself for non-partitioned relations), then users can easily
construct queries to get the results they want in different shapes, e.g.,

select pg_partition_root(c.oid), c.relname, pg_table_size(c.oid)
from pg_class c
order by 1

select pg_partition_root(c.oid), sum(pg_table_size(c.oid))
from pg_class c
group by 1

--
Peter Eisentraut http://www.2ndQuadrant.com/
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