From: | Florian Pflug <fgp(at)phlo(dot)org> |
---|---|
To: | "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov> |
Cc: | "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>, <drkp(at)csail(dot)mit(dot)edu>, <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: serializable read only deferrable |
Date: | 2010-12-08 20:02:41 |
Message-ID: | EE784482-CD44-495C-9B0F-4DC11A3B393A@phlo.org |
Views: | Raw Message | Whole Thread | Download mbox | Resend email |
Thread: | |
Lists: | pgsql-hackers |
On Dec8, 2010, at 20:39 , Kevin Grittner wrote:
> The standard is tricky to read, but my reading of it is that only
> "LOCAL" changes are allowed after the transaction is underway (which
> I *think* effectively means a subtransaction), and those can't make
> the setting less strict -- you're allowed to specify the same level
> or more strict. There would be no harm from the perspective of
> anything I'm working on to allow an in-progress transaction to be
> set to what it already has, but that seems to invite confusion and
> error more than provide a helpful feature, as far as I can tell.
> I'm inclined not to allow it except at the start of a
> subtransaction, but don't feel strongly about it.
Hm, I think being able to assert that the isolation level really is SERIALIZABLE by simply doing "SET TRANSACTION ISOLATION LEVEL SERIALIZABLE" would be a great feature for SSI.
Say you've written a trigger which enforces some complex constraint, but is correct only for SERIALIZABLE transactions. By simply sticking a "SET TRANSACTION ISOLATION LEVEL SERIALIZABLE" at the top of the trigger you'd both document that fact it is correct only for SERIALIZABLE transactions *and* prevent corruption should the isolation level be something else due to a pilot error. Nice, simply and quite effective.
BTW, I hope to find some time this evening to review your more detailed proposal for "serializable read only deferrable"
best regards,
Florian Pflug
From | Date | Subject | |
---|---|---|---|
Next Message | Dimitri Fontaine | 2010-12-08 20:04:17 | Re: Review: Extensions Patch |
Previous Message | Kevin Grittner | 2010-12-08 20:01:10 | Re: serializable read only deferrable |