Re: SSI and Hot Standby

Simon Riggs <simon@2ndQuadrant.com> writes:
> On Wed, 2011-01-19 at 19:05 -0600, Kevin Grittner wrote:
>> The idea is that whenever we see a valid snapshot which would yield
>> a truly serializable view of the data for a READ ONLY transaction,
>> we add a WAL record with that snapshot information. 

> You haven't explained why this approach is the way forwards. What other
> options have been ruled out, and why. The above approach doesn't sound
> particularly viable to me.

I'm pretty concerned about the performance implications, too.  In
particular that sounds like you could get an unbounded amount of WAL
emitted from a *purely read only* transaction flow.  Which is not
going to fly.
        regards, tom lane