On 08/10/2015 10:31 AM, Simon Riggs wrote:
> Freezing is not a necessary pre-condition for either of those things, I
> am happy to say. There is confusion here because for ( 1 ) the shrink
> was performed after freezing, but when you have access to the epoch
> there is no need for exhaustive freezing - only in special cases, as
> noted. If we are lucky those special cases will mean a massive reduction
> in I/O. For ( 2 ) a normal VACUUM is sufficient and as Robert observes,
> maybe just HOT is enough.
Yeah, saw your explanation on this on the other thread. Good point.
Question: does regular vacuum update the visibility map in the same way
vacuum freeze does?
--
Josh Berkus
PostgreSQL Experts Inc.
http://pgexperts.com