Robert Haas <> writes:
> On Sun, Feb 27, 2011 at 8:33 PM, Joachim Wieland <> wrote:
>> Remember that it's not only about saving shared memory, it's also
>> about making sure that the snapshot reflects a state of the database
>> that has actually existed at some point in the past.

> But you can do all of this with files too, can't you?  Just remove or
> truncate the file when the snapshot is no longer valid.

Yeah.  I think adopting a solution similar to 2PC state files is a very
reasonable way to go here.  This isn't likely to be a high-usage or
performance-critical feature, so it's not essential to keep the
information in shared memory for performance reasons.

                        regards, tom lane

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