=?ISO-8859-1?Q?C=E9dric_Villemain?= <cedric.villemain.deb...@gmail.com> writes:
> 2011/5/29 Tom Lane <t...@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.

                        regards, tom lane

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