Re: [PATCHES] pg_freespacemap question

Mark Kirkwood wrote:
> Christopher Kings-Lynne wrote:
> >>The point here is that if tuples require 50 bytes, and there are 20
> >>bytes free on a page, pgstattuple counts 20 free bytes while FSM
> >>ignores the page. Recording that space in the FSM will not improve
> >>matters, it'll just risk pushing out FSM records for pages that do
> >>have useful amounts of free space.
> >
> >Maybe an overloaded pgstattuple function that allows you to request FSM
> >behavior?
>
> That's a nice idea - could also do equivalently by adding an extra
> column "usable_free_space" or some such, and calculating this using FSM
> logic.

The current pgstattuple function scans the whole table, so I don't think
this is a good idea. Re: the overloaded function, I think the behaviors
are different enough to merit a separate function, with a different
name.

--
Alvaro Herrera http://www.CommandPrompt.com/
The PostgreSQL Company - Command Prompt, Inc.