Tom Lane wrote:
"Florian G. Pflug" <fgp@xxxxxxxx> writes:
Tom Lane wrote:
Until when? How would you synchronize the switchover?
Every snapshot would either contain the old, or the new version of
the corresponding pg_class tuple. The ones using the old version
couldn't possible be writer, only reader (TRUNCATE would still need
to acquire a lock that ensures that). New transactions started after
the commit of the truncate would see the new version, and use
the new datafile.
Wrong. *All* transactions read the system catalogs with SnapshotNow.
Ah, well that clearly kills my idea... Too bad...
I was fooled by the fact that most ddl-statements can be rolled back,
and assumed that this follows from using "normal" mvcc semantics when
reading the catalog tables.
Thanks for your explanations!
greetings, Florian Pflug
