Re: swapping relfilenodes (was: Re: locks in CREATE TRIGGER,

Bruce Momjian <pgman@candle.pha.pa.us> writes:
> In fact, would a truncate during a backup cause the backup to be
> inconsistent because it wouldn't be a true snapshot of the database at
> backup start time?  Seems so.

No, because pg_dump holds AccessShareLock on every table that it intends
to dump, thereby ensuring that TRUNCATE/CLUSTER/etc are held off.  The
proposal to weaken the locks that those operations take would in fact
break pg_dump.
        regards, tom lane