Re: autovacuum not prioritising for-wraparound tables

Jeff Janes <jeff.janes@gmail.com> wrote:
> Kevin Grittner <kgrittn@ymail.com> wrote:

>> So reducing vacuum_freeze_min_age not only helps minimize the
>> writes that are needed when autovacuum needs to scan the entire
>> heap,
>
> How does it do that? If the tuple doesn't need to frozen now
> because it was already frozen, that just means the write happened
> at a different time but it still happened.

There's a lot to be said for nibbling away at it during VM
autovacuum runs versus doing it in big chunks in heap-scan runs,
particularly if your BBU cache can absorb up to a certain amout
with no real pain, but causes major pain if the write cache fills.

-Kevin