| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
| Cc: | Gregory Stark <stark(at)enterprisedb(dot)com>, Manoel Henrique <mhenriquesgbd(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: Research/Implementation of Nested Loop Join optimization |
| Date: | 2008-07-26 00:44:49 |
| Message-ID: | 4383.1217033089@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> Tom Lane escribi:
>> Good joke, but to be serious: we expect that forward scans will result
>> in the kernel doing read-ahead, which will allow overlapping of
>> CPU work to process one page with the I/O to bring in the next page.
> I wonder if this is spoiled (or rather, the backwards case fixed) by the
> attempts to call posix_fadvise() on certain types of scan.
Yeah, I started wondering about that too after sending off the above.
The fadvise patch might eliminate the distinction ... on platforms where
fadvise exists and actually works well.
regards, tom lane
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