Patrick Hatcher <pathat@comcast.net> writes:
> Curious: Why would a DELETE FROM tablename work while a pg_dump is
> occurring but a TRUNCATE tablename will stay in a lock state until the
> pg_dump is complete?
TRUNCATE requires an exclusive lock on the table.
This is pretty much a no-free-lunch situation: if you want the pg_dump
to be able to dump all the rows that existed when it started, you can
hardly expect to be able to physically remove those rows meanwhile.
regards, tom lane