Re: Rapid Seek Devices (feature request)

On 16/08/2009 9:06 PM, NTPT wrote:

> So I suggest we should have "random_page_cost" and
> "Sequential_page_cost" configurable on per tablespace basis.

That strikes me as a REALLY good idea, personally, though I don't know
enough about the planner to factor in implementation practicalities and
any cost for people _not_ using the feature.

> 2: Many of that RSD devices are not so much reliable (power outage in
> ramdisk, weak auxillarity battery in i-ram like devices, block "wear
> out" in SSD).

[snip]

> ie read from fast tablespace, write to both fast and slow, reconstruct
> fast from slow if appropriate.

This can probably be done as well or better at the OS block layer, using
device-mapper or the `md' driver (on Linux).

What'd be interesting, though, would be if Pg had support for
auto-rebuilding indexes and (if/when explicit support is added)
materialized views if it finds the backing files are missing. This would
be helpful for such transient devices as RAM disks if you didn't want to
bother having physical storage backing it.

--
Craig Ringer