Re: heap_tuple_needs_freeze false positive

On Wed, Feb 1, 2012 at 8:01 PM, Alvaro Herrera <alvherre(at)alvh(dot)no-ip(dot)org> wrote:
> Suggested patch attached.  I'd backpatch this as far as it applies
> cleanly.

This is new code in 9.2, but it's modelled on heap_freeze_tuple(), which is old.

I'm not convinced that it's a bug. Suppose that xmax is set but is
hinted as invalid. We process the table and advanced relfrozenxid;
then, we crash. After recovery, it's possible that the hint bit is
gone (after all, setting hint bits isn't WAL-logged). Now we're in
big trouble, because the next CLOG lookup on that xmax value might not
happen until it's been reused, and we might get a different answer
than before.

--
Robert Haas
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