[HACKERS] access method: are disk pages mandatory?
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. -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] 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 -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] access method: are disk pages mandatory?
Heikki Linnakangas heikki.linnakan...@enterprisedb.com writes: On 23/06/10 18:17, Leonardo F wrote: 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. The bufpage.h comment is ancient and might not be 100% gospel anymore. However, I believe the buffer manager does assume that any page in shared buffers has a standard page header including LSN. It definitely assumes there's an LSN, and I think we have validity checks on the other page header fields somewhere inside ReadBuffer. You don't however need to use the item-and-item-pointer-array structure if it's not useful to you. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
