Re: autovacuum next steps, take 2

Tom Lane wrote:
> "Matthew T. O'Connor" <matthew@zeut.net> writes:
>> I'm not sure what you are saying here, are you now saying that partial 
>> vacuum won't work for autovac?  Or are you saying that saving state as 
>> Jim is describing above won't work?
> 
> I'm saying that I don't like the idea of trying to "stop on a dime" by
> saving the current contents of vacuum's dead-TID array to disk with the
> idea that we can trust those values 100% later.  Saving the array is
> expensive both in runtime and code complexity, and I don't believe we
> can trust it later --- at least not without even more expensive-and-
> complex measures, such as WAL-logging every such save :-(
> 
> I'm for stopping only after completing an index-cleaning pass, at the
> point where we empty the dead-TID array anyway.  If you really have to
> have "stop on a dime", just kill -INT the process, accepting that you
> will have to redo your heap scan since the last restart point.

OK, so if I understand correct, a vacuum of a table with 10 indexes on 
it can be interrupted 10 times, once after each index-cleaning pass? 
That might have some value, especially breaking up the work required to 
vacuum a large table. Or am I still not getting it?