Re: Commits 8de72b and 5457a1 (COPY FREEZE)

On Tue, Dec 4, 2012 at 3:38 PM, Jeff Davis <pgsql@j-davis.com> wrote:
> After reading that thread, I still don't understand why it's unsafe to
> set HEAP_XMIN_COMMITTED in those conditions. Even if it is, I would
> think that a sufficiently narrow case -- such as CTAS outside of a
> transaction block -- would be safe, along with some slightly broader
> cases (like BEGIN; CREATE TABLE; INSERT/COPY).

I haven't looked at the committed patch - which seemed a bit
precipitous to me given the stage the discussion was at - but I
believe the general issue with HEAP_XMIN_COMMITTED is that there might
be other snapshots in the same transaction, for example from open
cursors.

-- 
Robert Haas
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