| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Nicolas Barbier <nicolas(dot)barbier(at)gmail(dot)com> |
| Cc: | Markus Wanner <markus(at)bluegap(dot)ch>, Heikki Linnakangas <hlinnakangas(at)vmware(dot)com>, Yuri Levinsky <yuril(at)celltick(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Christopher Browne <cbbrowne(at)gmail(dot)com>, Robert Haas <robertmhaas(at)gmail(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, PostgreSQL Mailing Lists <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Hash partitioning. |
| Date: | 2013-06-27 21:35:53 |
| Message-ID: | CAMkU=1x0VBcNhunxF_qkVbOOSYvakpUi4O1aRBQKZHkR-U7f_Q@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Jun 27, 2013 at 9:35 AM, Nicolas Barbier
<nicolas(dot)barbier(at)gmail(dot)com>wrote:
>
> My reasoning was: To determine which index block to update (typically
> one in both the partitioned and non-partitioned cases), one needs to
> walk the index first, which supposedly causes one additional (read)
> I/O in the non-partitioned case on average, because there is one extra
> level and the lower part of the index is not cached (because of the
> size of the index).
But the "extra level" is up at the top where it is well cached, not at the
bottom where it is not.
Cheers,
Jeff
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