Re: Uniquness of ctid
| От | David G. Johnston |
|---|---|
| Тема | Re: Uniquness of ctid |
| Дата | |
| Msg-id | CAKFQuwYv8K3EtwXaYJhKiW5x54xJH_A=qy=gBXxzP4QvYpHc-g@mail.gmail.com обсуждение исходный текст |
| Ответ на | Uniquness of ctid (PG Doc comments form <noreply@postgresql.org>) |
| Список | pgsql-docs |
On Wed, Jul 19, 2023 at 2:31 PM PG Doc comments form <noreply@postgresql.org> wrote:
The following documentation comment has been logged on the website:
Page: https://www.postgresql.org/docs/15/ddl-system-columns.html
Description:
Hi,
Looking at the explanation abour ctid, it is "The physical location of the
row version within its table. "
From that line, I think ctid is unique in the table.
Unique but not stable - if you give your actual record an ID value the associated ctid for it may very well change over time and a given ctid can be associated with any number of IDs
And I also think ctid might be unique across the database since it is the
physical location.
The concept doesn't even apply - the value itself only makes sense within a given physical table. i.e., the table is implied. It's like saying "I live at 123 Main St." to someone. Sure in any given place there can only be a single 123 Main St. but that really isn't useful by itself. And to extend back to the previous point, you may live there now but you will likely have a different address in the future and someone else will have 123 Main St.
David J.
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