| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Andrew Dunstan <andrew(at)dunslane(dot)net> |
| Cc: | Kenneth Marshall <ktm(at)rice(dot)edu>, Robert Haas <robertmhaas(at)gmail(dot)com>, Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>, marcin mank <marcin(dot)mank(at)gmail(dot)com>, Andy Colson <andy(at)squeakycode(dot)net>, pgsql-hackers(at)postgresql(dot)org |
| Subject: | Re: unlogged tables |
| Date: | 2010-11-17 19:37:30 |
| Message-ID: | 18486.1290022650@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Andrew Dunstan <andrew(at)dunslane(dot)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
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