Re: hot_standby_feedback default and docs

On Tue, Sep 22, 2015 at 3:35 PM, Peter Eisentraut <peter_e@gmx.net> wrote:
> On 9/16/15 5:52 PM, Simon Riggs wrote:
>> IMHO the default is the best one at the current time.
>> See recovery_min_apply_delay.
>
> The applications of recovery_min_apply_delay are likely to be varied and
> specific, so there might not be a general answer to this, but wouldn't
> you want hot_standby_feedback on with it?  Because the longer you wait
> on the standby, the more likely it is that the primary will clean stuff
> away.

If min_recovery_apply_delay was set to 1 hour, and if the standby had
hot standby feedback turned on, wouldn't that mean that the master had
to not do any HOT pruning or vacuuming of tuples until they had been
dead for at least an hour?  That seems like it would be bad.

-- 
Robert Haas
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