Hi,
My reply to Gregory's comment didn't have any objections. I believe,
as I posted to Wiki page, latest posted patch is okay and waiting for
review.
2009/2/24 Robert Haas <robertmhaas@gmail.com>:
> On Sun, Jan 25, 2009 at 7:15 AM, Gregory Stark <stark@enterprisedb.com> wrote:
>> Koichi Suzuki <koichi.szk@gmail.com> writes:
>>
>>> Please find enclosed 2nd patch of pg_readahead which include a patch
>>> to bufer manager to skip prefetch of pages already in shared buffer.
>>
>> I'm a bit confused by this comment. PrefetchBuffer already checks if the page
>> is in shared buffers.
>>
>> What is tricky to avoid is prefetching the same page twice -- since the first
>> prefetch doesn't actually put it in shared buffers there's no way to avoid
>> prefetching it again unless you keep some kind of hash of recently prefetched
>> buffers.
>>
>> For the index scan case I'm debating about whether to add such a cache
>> directly to PrefetchBuffer -- in which case it would remember if some other
>> scan prefetched the same buffer -- or to keep it in the index scan code.
>
> Has this issue been resolved? Does this patch need more review?
> Because if so, I'm guessing it needs to happen RSN.
>
> ...Robert
>
--
------
Koichi Suzuki