"Nicholson, Brad (Toronto, ON, CA)" <bnichol...@hp.com> writes:
> I'm seeing something odd in my DB stats.  This is PG 9.2.4 on CentOS.  I know 
> the stats collector can be off at times, but I am curious as to why it would 
> be off in such a case.  I know that under heavy load the stats collector can 
> be off sometimes, but this system was barely doing anything (CPU ~ 90% idle). 
>  PG didn't shutdown at all either.

Most likely there was some DML happening concurrently with a VACUUM or
ANALYZE at some point in the past.  VACUUM/ANALYZE update the live and
dead tuple counts based on what they saw, but a transaction that added
such tuples (that were counted by the maintenance op) could commit after
that happens, and then you end up with double-counted tuples.

                        regards, tom lane


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