On Fri, Apr 24, 2015 at 4:09 PM, Jim Nasby <Jim.Nasby@bluetreble.com>
wrote:>>> When I read that I think about something configurable at
>>> relation-level.There are cases where you may want to have more
>>> granularity of this information at block level by having the VM slots
>>> to track less blocks than 32, and vice-versa.
>>
>> What are those cases? To me that sounds like making things
>> complicated to no obvious benefit.
>
> Tables that get few/no dead tuples, like bulk insert tables. You'll have
> large sections of blocks with the same visibility.
I don't see any reason why that would require different granularity.
> I suspect the added code to allow setting 1 bit for multiple pages without
> having to lock all those pages simultaneously will probably outweigh making
> this a reloption anyway.
That's a completely unrelated issue.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
