Jim Nasby wrote:
> That would be the minimal-impact version, yes. But I suspect if we went
> through the trouble to do that, it would be just as easy to attempt the
> freeze regardless of what scan_all is set to.
You mean if !scan_all we conditional-get the cleanup lock, if we get it
then prune, if not then freeze? That seems nice on paper but I think
it's useless because unless scan_all is true, then relfrozenxid doesn't
advance anyway.
> What I wish I knew is whether this problem was worth worrying about or not.
> Hopefully the extra logging in 9.5 will shed some light at some point...
As I recall, Andres says it isn't, but I have recollections of scans
that take a very long time to finish because they keep running into a
vacuum that has a page locked.
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Álvaro Herrera http://www.2ndQuadrant.com/
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