| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | Peter Geoghegan <pg(at)bowt(dot)ie> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org>, Jan Wieck <jan(at)wi3ck(dot)info>, Gregory Smith <gregsmithpgsql(at)gmail(dot)com>, John Naylor <john(dot)naylor(at)enterprisedb(dot)com>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi> |
| Subject: | Re: The Free Space Map: Problems and Opportunities |
| Date: | 2021-08-20 20:30:38 |
| Message-ID: | CA+TgmoYP5n3WGRWtDBJWcRfJ05zkoUVqK3GAPyTXb7XkjhTn3A@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Fri, Aug 20, 2021 at 3:40 PM Peter Geoghegan <pg(at)bowt(dot)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
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