From: | Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | Masahiko Sawada <sawada(dot)mshk(at)gmail(dot)com>, Peter Geoghegan <pg(at)bowt(dot)ie>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
Subject: | Re: Rename dead_tuples to dead_items in vacuumlazy.c |
Date: | 2021-11-24 14:51:12 |
Message-ID: | 202111241451.47dzrgdmsuyt@alvherre.pgsql |
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Lists: | pgsql-hackers |
On 2021-Nov-24, Robert Haas wrote:
> Hmm. I think in my model an item and an item pointer and a line
> pointer are all the same thing, but a TID is different. When I talk
> about a TID, I mean the location of an item pointer, not its contents.
> So a TID is what tells me that I want block 5 and the 4th slot in the
> item pointer array. The item pointer tells me that the associate tuple
> is at a certain position in the page and has a certain length.
OK, but you can have item pointers that don't have any item.
LP_REDIRECT, LP_DEAD, LP_UNUSED item pointers don't have items.
--
Álvaro Herrera Valdivia, Chile — https://www.EnterpriseDB.com/
"Nunca confiaré en un traidor. Ni siquiera si el traidor lo he creado yo"
(Barón Vladimir Harkonnen)
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