Re: The Free Space Map: Problems and Opportunities

On Fri, Aug 20, 2021 at 3:40 PM Peter Geoghegan <pg@bowt.ie> wrote:
> My concern here is really the data structure and its overall
> complexity. If there has to be an explicit state for every page on the
> FSM, then this new FSM needs to merge freelists that have been emptied
> into that structure, and needs to handle the question of which
> structure (map or free lists) is currently authoritative for a given
> heap page. That's a lot of complexity compared to just forgetting the
> free lists that are known to be fully closed, which will probably be
> very common. That can work a little like discarding old UNDO -- it can
> be simple and cheap *because* it's largely logical and implicit at the
> level of the physical data structures.

I don't think I understand the data structure that you have in mind
well enough to comment intelligently.

-- 
Robert Haas
EDB: http://www.enterprisedb.com