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

Tom Lane wrote:
> 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.

Oh, it pre-locks.  I didn't know that.

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