Re: Experimental ARC implementation

Tom Lane wrote:
> Bruce Momjian <pgman@candle.pha.pa.us> writes:
> > Have you considered having the background writer check the pages it is
> > about to write to see if they can be added to the FSM, thereby reducing
> > the need for vacuum?
> 
> The 7.4 rewrite of FSM depends on the assumption that all the free space
> in a given relation is reported to FSM in one batch (ie, at the end of a
> VACUUM pass).  This solves problems in both speed (page-at-a-time update
> of FSM was horrendously expensive) and space allocation policy (we now
> use the number of "interesting" pages in each relation as input
> information for the allocation policy).  To do anything like the above,
> you'd need to find different solutions to these problems.

Yea, shame.  I never liked sequentially scanning a huge table just to
find the few free tuples.

--  Bruce Momjian                        |  http://candle.pha.pa.us pgman@candle.pha.pa.us               |  (610)
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