The problem of freezing is painful, but not impossible, which is why we have held out so long.
The problem of very long lived snapshots is coming closer at the same speed as freezing; there is no solution to that without 64-bit xids throughout whole infrastructure, or CSNs.
The opportunity for us to have SQL Standard historical databases becomes possible with 64-bit xids, or CSNs. That is a high value goal.
I personally now think we should thoroughly investigate 64-bit xids. I don't see this as mere debate, I see this as something that we can make a patch for and scientifically analyze the pros and cons through measurement.
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Simon Riggs http://www.2ndQuadrant.com/ PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services