From: | Craig Ringer <craig(at)postnewspapers(dot)com(dot)au> |
---|---|
To: | Alex Besogonov <alex(dot)besogonov(at)gmail(dot)com> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Ability to 'fork' a running transaction? |
Date: | 2010-01-31 14:02:33 |
Message-ID: | 4B658D79.2080905@postnewspapers.com.au |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-general |
On 31/01/2010 9:06 PM, Alex Besogonov wrote:
> On Sun, Jan 31, 2010 at 7:25 AM, Craig Ringer
> <craig(at)postnewspapers(dot)com(dot)au> wrote:
>>> However, here lies the problem: I need to use SERIALIZABLE transaction
>>> isolation level, and AFAIK it's not possible to make several database
>>> connections to share the same exact view of the database.
>> I've noticed some talk on -HACKERS of finding ways to make this possible.
>> It's needed for parallel pg_dump, among other things.
> Actually, I the program I'm writing behaves exactly like parallel
> pg_dump from PostgreSQL's point of view.
>
> I've found this discussion in -HACKERS:
> http://osdir.com/ml/pgsql-hackers/2009-11/msg00265.html It seems, it's
> exactly what I need to do. I might try to contribute a patch.
Well, if you're able to that'd be absolutely brilliant :-)
>> It's not clear if it'd work for non-read-only transactions; I didn't notice
>> that being discussed, and don't know enough about it to have an opinion of
>> my own. Still, it's worth looking into for the future.
> It should be possible to do this for read/write transactions as well.
>
>>> So, is there a way to somehow stop all mutating operations?
>> Take explicit locks on the resources of interest that are permissive enough
>> to be shared with other read transactions, but not to permit writes.
> I thought about it, but it's too deadlock-prone. I need to lock the
> whole database, and if I do this table-by-table then I'll almost
> certainly generate a deadlock.
Not if you specify, and stick to, a strict lock acquisition order and
never try to upgrade a lock you already hold.
--
Craig Ringer
From | Date | Subject | |
---|---|---|---|
Next Message | Craig Ringer | 2010-01-31 14:06:44 | Re: Best practice for file storage? |
Previous Message | Alex Besogonov | 2010-01-31 13:06:41 | Re: Ability to 'fork' a running transaction? |