Re: Unlogged vs. In-Memory

On Tue, May 3, 2011 at 20:06, Thom Brown <thom@linux.com> wrote:
> On 3 May 2011 19:02, Rob Wultsch <wultsch@gmail.com> wrote:
>> Can Unlogged tables be located on a table space mount on a ram fs
>> without hosing the instance if the server gets bounced?
>
> No more than anything else in a RAM filesystem.  There are of course
> battery-backed RAM disk devices people can use, but those are a
> special case.

I think you're missing the scenario Rob is talking about. I think he
mentions the sequence:

CREATE TABLESPACE junk LOCATION '/tmp/junk';
CREATE UNLOGGED TABLE meh(a int) TABLESPACE junk;
<stop server>
rm -rf /tmp/junk/*
<start server>
postgres=# select * from meh;
ERROR:  could not open file
"pg_tblspc/16434/PG_9.1_201104251/12008/16435": No such file or
directory

Now if the tablespace contains *only* unlogged tables, it should at
least theoretically be possible to recover from this situation on
startup, I think. But it's not now. Anybody have an idea about how
much work that would be?

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 Magnus Hagander
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