Re: Minimum tuple threshold to decide last pass of VACUUM

Alvaro Herrera <alvherre@2ndquadrant.com> writes:
> Simon Riggs wrote:
>> * For emergency anti-wraparound VACUUMs we shouldn't scan indexes at all,
>> since they aren't critical path activities at that point

> It is not possible to skip scanning indexes completely, unless no tuples
> are to be removed from the heap.

Right.

> But actually this is an interesting point and I don't think we do this:
> if in emergency mode, maybe we shouldn't try to remove any dead tuples
> at all, and instead only freeze very old tuples.

+1 ... not sure if that's what Simon had in mind exactly, but it seems
like a correct statement of what he was getting at.
        regards, tom lane