Re: access method: are disk pages mandatory?

On 23/06/10 18:17, Leonardo F wrote:
> in bufpage.h:
>
> "all blocks written out by an access method must be disk pages"
>
> but in
> http://www.postgresql.org/docs/8.4/static/storage-page-layout.html
>
> "Actually, index access methods need not use this page format. All the
> existing index methods do use this basic format, but the data kept on
> index metapages usually doesn't follow the item layout rules."
>
> I'm not getting it: am I supposed to use the "disk page format" when
> writing an index access method, or it's just a "good practice" because
> it makes the handling easier? Given the docs it looks "recommended",
> but the comment on the code sounds more "mandatory".

It's recommened because it makes life easier. Even if you don't use the 
normal page format, I think you need to have the LSN at the beginning of 
the page. The rest is up to you.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com