On Sun, May 29, 2011 at 8:10 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Cédric Villemain <cedric.villemain.debian@gmail.com> writes:
>> 2011/5/29 Tom Lane <tgl@sss.pgh.pa.us>:
>>> OK, do you like the attached version of that logic? (Other fragments
>>> of the patch as before.)
>
>> The idea was that remove only one page from the VACUUM will prevent
>> relfrozenxid update and reltuples (and relpages) update.
>> Now, I beleive that once we've skip at least one page thanks to
>> SKIP_PAGES_THRESHOLD, then we should be more agressive and remove as
>> many as possible pages from the VACUUM, tks to the VM.
>
> That would require proof, not just suggestion. Skipping pages will
> defeat the OS read-ahead algorithm, and so could easily cost more than
> reading them.
>
My worry is what we have right now is also based on just assumptions
and gut feelings rather than any numbers.
Thanks,
Pavan
--
Pavan Deolasee
EnterpriseDB http://www.enterprisedb.com
