Re: serializable read only deferrable

From: "Kevin Grittner" <Kevin(dot)Grittner(at)wicourts(dot)gov>
To: "Florian Pflug" <fgp(at)phlo(dot)org>
Cc: <drkp(at)csail(dot)mit(dot)edu>,<pgsql-hackers(at)postgresql(dot)org>, "Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Subject: Re: serializable read only deferrable
Date: 2010-12-08 20:12:38
Message-ID: 4CFF9256020000250003848C@gw.wicourts.gov
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Florian Pflug <fgp(at)phlo(dot)org> wrote:

> 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.

It would be great to have a way within a trigger, or possibly other
functions, to assert that the transaction isolation level is
serializable. What gives me pause here is that the standard allows
you to specify a more strict transaction isolation level within a
subtransaction without error, so this way of spelling the feature is
flirting with rather nonstandard behavior.

Is there maybe a better way to check this?

-Kevin

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