Re: Visibility map and freezing

Jeff Davis wrote:
> On Wed, 2009-01-07 at 09:34 +0200, Heikki Linnakangas wrote:
>> autovacuum_freeze_max_age -> autovacuum_freeze_scan_age
>> vacuum_freeze_max_age -> vacuum_freeze_scan_age
>> vacuum_freeze_min_age -> vacuum_freeze_tuple_age
>>
>> *_scan_age settings control when the table is fully scanned to freeze
>> tuples and advance relfrozenxid, and vacuum_freeze_tuple_age controls
>> how old a tuple needs to be to be frozen. One objection is that you can
>> read "freeze_scan" to mean that a scan is frozen, like a tuple is
>> frozen. Any better ideas?
>
> I see what you mean about the possible misinterpretation, but I think
> it's a big improvement, and I don't have a better suggestion.

Thinking about this some more, I'm not too happy with those names
either. vacuum_freeze_scan_age and autovacuum_freeze_scan_age don't mean
quite the same thing, like vacuum_cost_delay and
autovacuum_vacuum_cost_delay do, for example.

I'm now leaning towards:

autovacuum_freeze_max_age
vacuum_freeze_table_age
vacuum_freeze_min_age

where autovacuum_freeze_max_age and vacuum_freeze_min_age are unchanged,
and vacuum_freeze_table_age is the new setting that controls when VACUUM
or autovacuum should perform a full scan of the table to advance
relfrozenxid.

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com