From: | Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp> |
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To: | Nikita Malakhov <hukutoc(at)gmail(dot)com> |
Cc: | 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: | 2023-07-07 08:21:36 |
Message-ID: | 20230707172136.9dc1af99e3e237187c2b3d02@sraoss.co.jp |
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Lists: | pgsql-hackers |
Hi Nikita,
On Wed, 5 Jul 2023 17:49:20 +0300
Nikita Malakhov <hukutoc(at)gmail(dot)com> wrote:
> Hi!
>
> I like the idea of having a standard function which shows a TOAST value ID
> for a row. I've used my own to handle TOAST errors. Just, maybe, more
> correct
> name would be "...value_id", because you actually retrieve valueid field
> from the TOAST pointer, and chunk ID consists of valueid + chunk_seq.
Thank you for your review!
Although, the retrieved field is "va_valueid" and it is called "value ID" in the
code, I chose the name "..._chunk_id" because I found the description in the
documentation as followings:
-------------
Every TOAST table has the columns chunk_id (an OID identifying the particular TOASTed value), chunk_seq (a sequence number for the chunk within its value), and chunk_data (the actual data of the chunk). A unique index on chunk_id and chunk_seq provides fast retrieval of the values. A pointer datum representing an out-of-line on-disk TOASTed value therefore needs to store the OID of the TOAST table in which to look and the OID of the specific value (its chunk_id)
-------------
https://www.postgresql.org/docs/devel/storage-toast.html
Here, chunk_id defined separately from chunk_seq. Therefore, I wonder
pg_column_toast_chunk_id would be ok. However, I don't insist on this
and I would be happy to change it if the other name is more natural for users.
Regards,
Yugo Nagata
>
> --
> Regards,
> Nikita Malakhov
> Postgres Professional
> The Russian Postgres Company
> https://postgrespro.ru/
--
Yugo NAGATA <nagata(at)sraoss(dot)co(dot)jp>
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