Re: TRUNCATE SERIALIZABLE and frozen COPY

On 8 November 2012 17:07, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Wed, Nov 7, 2012 at 10:34 AM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> For 9.2 we discussed having COPY setting tuples as frozen. Various
>> details apply.
>> Earlier threads:
>> "RFC: Making TRUNCATE more "MVCC-safe"
>> "COPY with hints, rebirth"
>>
>> I was unhappy with changing the behaviour of TRUNCATE, and still am.
>> So the proposal here is to have a specific modifier on TRUNCATE
>> command that makes it MVCC safe by throwing a serialization error.
>
> I don't think I understand the proposal. Under what circumstances
> would it throw a serialization error?

If you ask for TRUNCATE SERIALIZABLE then if someone asks for data in
the table and has a snapshot that can see earlier data then it will
throw a serializable error. So its a new kind of TRUNCATE that is MVCC
safe.

--
Simon Riggs http://www.2ndQuadrant.com/
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