Re: Free space management within heap page

On 1/23/07, Heikki Linnakangas <heikki(at)enterprisedb(dot)com> wrote:
>
> Pavan Deolasee wrote:
>
> > So during a sequential or index scan, if a tuple is found to be dead,
> the
> > corresponding line pointer is marked "unused" and the space is returned
> > to a
> > free list. This free list is maintained within the page. A linked-list
> can
> > be used for this purpose and the special area of the heap-page can be
> used
> > to track the fragment list. We can maintain some additional information
> > about the fragmented space such as, total_free_space, max_fragment_size,
> > num_of_fragments etc in the special area.
>
> Maintaining a list like that seems like a lot of hassle to me. Instead,
> you could just scan the line pointers looking for a dead tuple of the
> right size. We already have to scan the line pointers when inserting to
> find a free line pointer.

That's a good suggestion. Just to avoid useless scans when there is no
fragment which can accommodate the new tuple, we may have some book keeping
information in the special area though.

Thanks,
Pavan

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