Re: ToDo: show size of partitioned table

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От Pavel Stehule
Тема Re: ToDo: show size of partitioned table
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Msg-id CAFj8pRC3FTx=1-Xsg5QWqK1=Fp9iS7oJROOYApiihGzOJqBuEw@mail.gmail.com
обсуждение исходный текст
Ответ на Re: ToDo: show size of partitioned table  (Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>)
Ответы Re: ToDo: show size of partitioned table  (Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>)
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2018-06-20 7:44 GMT+02:00 Amit Langote <Langote_Amit_f8@lab.ntt.co.jp>:
On 2018/06/02 0:15, Ashutosh Bapat wrote:
> I think we should at least display "Type" as "partitioned table" for a
> partitioned table, so that it's easy to understand why the size is 0;
> partitioned tables do not hold any data by themselves.

There was a long discussion last year (during PG 10 beta period), such as
[1], and it seems most of us agreed to doing the above.  Maybe, we should
finally do it for PG 12, if not PG 11.

Regarding showing the size of partitioned tables, there are many opinions
and it's not clear if showing it in \dt itself is appropriate.  For one,
there is no pg_relation_size() or pg_table_size() equivalent in the
backend for aggregating the size of all tables in a partition tree and I
think people are not quite on board about having such a function in the
backend [2].

Now, the number of partitions can be low, but if the Postgres can better process high number of partitions, then for some tables we can have hundreds partitions.

Then usual \dt can be not too much usable. The aggregation can be done on client side. But maybe this idea is premature. Now, for PG 12, we can start with

\dtP+ command for showing partition tables only with aggregate size via all related partitions.

Is it acceptable idea?

Regards

Pavel

Thanks,
Amit

[1]
https://www.postgresql.org/message-id/flat/7dfc13c5-d6b7-1ff1-4bef-d75d6d2f76d9%40lab.ntt.co.jp

[2]
https://www.postgresql.org/message-id/flat/495cec7e-f8d9-7e13-4807-90dbf4eec4ea%40lab.ntt.co.jp


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