On 2/13/07, Tom Lane <[EMAIL PROTECTED]> wrote:
Heikki Linnakangas <[EMAIL PROTECTED]> writes: > Hannu Krosing wrote: >> Are we actually doing that ? I.E are null bitmaps really allocated in 1 >> byte steps nowadays ? > Yes. Not really; we still have to MAXALIGN at the end of the bitmap. The point is that you can get 8 bits in there before paying the first additional MAXALIGN increment. It's all moot anyway since 8 bits isn't enough for a pointer ...
We could live with 8 bits actually. We can store only the least significant 8 bits of the pointer. It would point to a set of tuples and we may need to search within that set to find the required tuple. This would still be better than scanning the entire page. But I agree that utilizing those 8 bits would result in a penalty for tables with few columns. Thanks, Pavan -- EnterpriseDB http://www.enterprisedb.com
