Can someone explain this: http://dev.rubyonrails.org/changeset/7419
there’s no background information linked in via the changeset. As far as I can tell, this change will significantly affect the baseline performance of every existing deployed rails application.
Is this a correct assessment?
b.
No,
The cache is still (should be) enabled for actionpack, if it's not, please let us know.
It was disabled 'by default' for non-actionpack clients as the caching code adds overhead , and if caching isn't going to be used it's needless. The intent is to let batch scripts etc opt out.
To quote jeremy just before committing this:
query cache code enabled, but no cache in use: 30 sec, query cache code enabled and cache in use: 28 sec, query cache code disabled and no cache in use: 18 sec
So the overhead was at least non-trivial.