On Oct 22, 2010, at 15:12, Max Vlasov wrote:

> As for your initial question, I think fragmentation evaluation is possible
> with the help of VFS. I'd keep a total sum of of absolute difference between
> consequent read offsets for xRead operation. In this case if some xRead
> request reads 1024 bytes at the 4096 offset and the next xRead reads
> something at 5120 (4096 +1024) this will add 0 to the sum, but if the next
> read something at 8192, this will add 3072 = (8192 - (4096 +1024)). If this
> implemented, you will be able to see how this value changes for some of your
> SELECT and maybe evaluate it on per record basis. If it's more like some
> threshold value, ok, peform VACUUM


        This sounds like a *really* awesome idea.  I know exactly what 
operations I'm doing that *shouldn't* generally seek and I can keep some stats 
on that.

        Thanks a lot.

-- 
Dustin Sallings

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