From: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>
To: Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>
To: Michael Paquier <michael.paquier@gmail.com>
To: David Rowley <david.rowley@2ndquadrant.com>
Cc: Robert Haas <robertmhaas@gmail.com>
Cc: Pg Hackers <pgsql-hackers@postgresql.org>
Subject: Re: pg_(total_)relation_size and partitioned tables
Date: Thu, 28 Dec 2017 14:03:11 -0500
Message-ID: <d5323242-b571-9317-1e5b-ee5fd96c2f4a@2ndquadrant.com> (raw)
In-Reply-To: <1a78dea4-36b7-afb7-b3f3-1b4ff319fbb4@lab.ntt.co.jp>
References: <495cec7e-f8d9-7e13-4807-90dbf4eec4ea@lab.ntt.co.jp>
<CA+TgmobG69Nf4E+VKcojXZQa9FRsbr7Dd+NORJRFMh5Umer98w@mail.gmail.com>
<CAKJS1f9Rev615s4k7JhUsqwu-3CjR0xB2F0qpZ5fvQe+mxke0w@mail.gmail.com>
<CAB7nPqQtNv5DLD9pXMWcT2VcsJqOnRUNBKekAapYiJxV4t=tyg@mail.gmail.com>
<CAB7nPqTKy7HRpUM0_vMjGPkM6h6pR86Aegsw+MTmzxWr3-D-tg@mail.gmail.com>
<1a78dea4-36b7-afb7-b3f3-1b4ff319fbb4@lab.ntt.co.jp>
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/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Reply to all the recipients using the --to and --cc options:
reply via email
To: pgsql-hackers@postgresql.org
Cc: peter.eisentraut@2ndquadrant.com, Langote_Amit_f8@lab.ntt.co.jp, michael.paquier@gmail.com, david.rowley@2ndquadrant.com, robertmhaas@gmail.com
Subject: Re: pg_(total_)relation_size and partitioned tables
In-Reply-To: <d5323242-b571-9317-1e5b-ee5fd96c2f4a@2ndquadrant.com>
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
This inbox is served by DDX for PostgreSQL; see mirroring instructions
for how to clone and mirror all data and code used for this inbox