Re: Hint Bits and Write I/O

Kevin Grittner wrote:
>>>> On Wed, May 28, 2008 at 6:26 PM, in message
> <483DEA2D(dot)3010704(at)phlo(dot)org>,
> "Florian G. Pflug" <fgp(at)phlo(dot)org> wrote:
>
>> I think we should put some randomness into the decision,
>> to spread the IO caused by hit-bit updates after a batch load.
>
> Currently we have a policy of doing a VACUUM FREEZE ANALYZE on a table
> after a bulk load, or on the entire database after loading a pg_dump
> of a database. We do this before putting the table or database into
> production. This avoids surprising clusters of writes at
> unpredictable times. Please don't defeat that. (I'm not sure whether
> your current suggestion would.)

No, VACUUM (and therefore VACUUM FREEZE) dirty all buffers they set hit
bits on anyway, since they also update the xmin values. But a more
IO-friendly approach to setting hit bits might make that VACUUM FREEZE
step unnecessary ;-)

regards, Florian Pflug