Re: a bit more precise MaxOffsetNumber
| От | Robert Haas |
|---|---|
| Тема | Re: a bit more precise MaxOffsetNumber |
| Дата | |
| Msg-id | BANLkTimCATSV+dZw-OKcEPttgnRRTOedkA@mail.gmail.com обсуждение исходный текст |
| Ответ на | a bit more precise MaxOffsetNumber (Tomas Vondra <tv@fuzzy.cz>) |
| Ответы |
Re: a bit more precise MaxOffsetNumber
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| Список | pgsql-hackers |
2011/4/30 Tomas Vondra <tv@fuzzy.cz>: > I've been digging in the sources, and I've noticed the MaxOffsetNumber > is defined (in storage/off.h) like this > > (BLCKSZ / sizeof(ItemIdData)) > > I guess it might be made a bit more precise by subtracting the header > like this > > (BLCKSZ - offsetof(PageHeaderData, pd_linp) / sizeof(ItemIdData)) > > although the difference is negligible (2048 vs 2042 for 8kB pages). I guess we could do that, but I'm not sure there's much point. It's also not entirely clear that this would actually work out to a win, because of the issues discussed in the "When can/should we prune or defragment?" section of src/backend/access/heap/README.HOT We could probably figure this out with some careful testing, but I'm not sure it's worth the effort. -- Robert Haas EnterpriseDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
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