Re: unlogged tables

Tom Lane <tgl@sss.pgh.pa.us>

From: Tom Lane <tgl@sss.pgh.pa.us>

To: Andrew Dunstan <andrew@dunslane.net>

Cc: Kenneth Marshall <ktm@rice.edu>, Robert Haas <robertmhaas@gmail.com>, Heikki Linnakangas <heikki.linnakangas@enterprisedb.com>, marcin mank <marcin.mank@gmail.com>, Andy Colson <andy@squeakycode.net>, pgsql-hackers@postgresql.org

Date: 2010-11-17T19:37:30Z

Lists: pgsql-hackers

Andrew Dunstan <andrew@dunslane.net> writes:
> On 11/17/2010 02:22 PM, Kenneth Marshall wrote:
>> I would be fine with only having a safe shutdown with unlogged tables
>> and skip the checkpoint I/O all other times.

> Yeah, I was just thinking something like that would be good, and should 
> overcome Robert's objection to the whole idea.

I don't think you can fsync only in the shutdown checkpoint and assume
your data is safe, if you didn't fsync a write a few moments earlier.

Now, a few minutes ago Robert was muttering about supporting more than
one kind of degraded-reliability table.  I could see inventing
"unlogged" tables, which means exactly that (no xlog support, but we
still checkpoint/fsync as usual), and "unsynced" tables which
also/instead suppress fsync activity.  The former type could be assumed
to survive a clean shutdown/restart, while the latter wouldn't.  This
would let people pick their poison.

			regards, tom lane