On Fri, 2005-05-20 at 14:41 +0900, ITAGAKI Takahiro wrote:
> LOG: FreeSpace for "public.accounts" becomes empty. (stored=1, avg=159, min=128)

Looks useful to me, until we patch up FSMs more fully in the future.

Might need rewording. Stored -> stored pages, Avg -> Avg Row Length.
Probably should be a DEBUG1 log line also.

It would be even more useful if this was signalled (perhaps to stats) in
such a way that autovacuum could act upon this knowledge.

> Furthermore, this patch detaches empty fsmpages then.
> Freespaces keep being scanned after they empties,
> but it seems to be bootless effort.

Does that do anything useful though?

I thought we don't reallocate until VACUUM time, whereupon we identify
any empty slots and reuse them. Who cares whether we deallocate earlier?

Best Regards, Simon Riggs



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Simon Riggs <simon@2ndquadrant.com> wrote:

> > Furthermore, this patch detaches empty fsmpages then.
> Does that do anything useful though?
> I thought we don't reallocate until VACUUM time, whereupon we identify
> any empty slots and reuse them. Who cares whether we deallocate earlier?

Yes, we cannot reuse them until next VACUUM.
But I think it is a problem that FSMs keep being scanned after they are almost empty.
In such a case, most stored pages are touched whenever new pages
are requested. I intended to cut FSMs earlier in order to omit the scans.


---
ITAGAKI Takahiro
NTT Cyber Space Laboratories


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