On Fri, Dec 10, 2010 at 12:21 PM, Daniel Loureiro <loureirorg@gmail.com> wrote:
>>> Most of you already know I am new to this list and newer to any OSS
>>> development. However, while browsing the source code (of 9.0.1) I find
>>> that there is only one way to store relations on disk - the magnetic
>>> disk.
>
>>The fact that it's called md.c is a hangover from the '80s. These days,
>>the logic that the Berkeley guys envisioned being at that code level
>>is generally in kernel device drivers. md.c can drive anything that
>>behaves as a block device + filesystem, which is pretty much everything
>>of interest.
>
> I believe that PostgreSQL was been developed and optimized for
> sequential access. To get full advantage of SSDs its necessary to
> rewrite almost the whole project - there are so much code written with
> the sequential mechanism in mind.
I don't think that that is true at all. If you tell the planner that
a random page and a sequential page have the same cost, does it not
believe you?
Of course if you do a full table scan because their are no better
options, then it scans sequentially. But you have to scan the pages
in *some* order, and it is hard to see how something other than
sequential would be systematically better.
Cheers,
Jeff