On 2/13/07, Tom Lane <tgl@sss.pgh.pa.us> wrote: Heikki Linnakangas <heikki@enterprisedb.com> 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
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