Re: Free space management within heap page

Pavan Deolasee wrote:
> I am thinking that maintaining fragmented free space within a heap page
> might be a good idea. It would help us to reuse the free space ASAP without
> waiting for a vacuum run on the page. This in turn will lead to lesser heap
> bloats and also increase the probability of placing updated tuple in the
> same heap page as the original one.

Agreed.

> 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.

--   Heikki Linnakangas  EnterpriseDB   http://www.enterprisedb.com