--On 4. November 2014 17:18:14 -0500 Tom Lane <[email protected]> wrote:
Yeah, and I think that it's entirely reasonable for rewriting ALTER TABLEs
to update the xmin of the rewritten tuples; after all, the output data
could be arbitrarily different from what the previous transactions put
into the table. But that is not the question here. If the COPY blocks
until the ALTER completes --- as it must --- why is its execution snapshot
not taken *after* the lock is acquired?
COPY waits in DoCopy() but its snapshot gets acquired in PortalRunUtility()
earlier. SELECT has it's lock already during transform/analyse phase and
its snapshot is taken much later. Looks like we need something that
analyses a utility statement to get its lock before executing.
--
Thanks
Bernd
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