Russell Smith wrote:
>On Fri, 18 Feb 2005 04:38 pm, Kevin Brown wrote:
>
>
>>Tom Lane wrote:
>>
>>
>>> No, the entire point of this discussion is to whup the DBA upside the
>>>
>>>head with a big enough cluestick to get him to install autovacuum.
>>>
>>>Once autovacuum is default, it won't matter anymore.
>>>
>>>
>>I have a concern about this that I hope is just based on some
>>misunderstanding on my part.
>>
>>My concern is: suppose that a database is modified extremely
>>infrequently? So infrequently, in fact, that over a billion read
>>transactions occur before the next write transaction. Once that write
>>transaction occurs, you're hosed, right? Autovacuum won't catch this
>>because it takes action based on the write activity that occurs in the
>>tables.
>>
>>So: will autovacuum be coded to explicitly look for transaction
>>wraparound, or to automatically vacuum every N number of transactions
>>(e.g., 500 million)?
>>
>>
>autovacuum already checks for both Transaction wraparound, and table updates.
>It vacuums individual tables as they need it, from a free space/recovery point of view.
>
>It also does checks to ensure that no database is nearing transaction wraparound, if it
>is, it initiates a database wide vacuum to resolve that issue.
>
Right, the check that autovacuum does for wraparound is totally separate
from the monitoring of inserts updates and deletes.