Re: pg_column_toast_chunk_id: a function to get a chunk ID of a TOASTed value

From: Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp>
To: Nathan Bossart <nathandbossart(at)gmail(dot)com>
Cc: jian he <jian(dot)universality(at)gmail(dot)com>, Sergei Kornilov <sk(at)zsrv(dot)org>, Nikita Malakhov <hukutoc(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: pg_column_toast_chunk_id: a function to get a chunk ID of a TOASTed value
Date: 2024-03-08 06:31:55
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On Thu, 7 Mar 2024 16:56:17 -0600
Nathan Bossart <nathandbossart(at)gmail(dot)com> wrote:

> On Mon, Feb 05, 2024 at 04:28:23PM +0900, Yugo NAGATA wrote:
> > On Thu, 1 Feb 2024 17:59:56 +0800
> > jian he <jian(dot)universality(at)gmail(dot)com> wrote:
> >> v6 patch looks good.
> >
> > Thank you for your review and updating the status to RwC!
> I think this one needs a (pretty trivial) rebase. I spent a few minutes
> testing it out and looking at the code, and it seems generally reasonable

Thank you for your review.
I've attached a rebased patch.

> to me. Do you think it's worth adding something like a
> pg_column_toast_num_chunks() function that returns the number of chunks for
> the TOASTed value, too?

If we want to know the number of chunks of a specified chunk_id,
we can get this by the following query.

postgres=# SELECT id, (SELECT count(*) FROM pg_toast.pg_toast_16384 WHERE chunk_id = id)
FROM (SELECT pg_column_toast_chunk_id(v) AS id FROM t);

id | count
16389 | 3
16390 | 287
(2 rows)

However, if there are needs for getting such information in a
simpler way, it might be worth making a new function.

Yugo Nagata

> --
> Nathan Bossart
> Amazon Web Services:

Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp>

Attachment Content-Type Size
v7-0001-Add-pg_column_toast_chunk_id-function.patch text/x-diff 6.5 KB

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