Re: Hot Standby query cancellation and Streaming Replication integration

Dimitri Fontaine wrote:
> Tom Lane <tgl@sss.pgh.pa.us> writes:
> > Well, as Heikki said, a stop-and-go WAL management approach could deal
> > with that use-case.  What I'm concerned about here is the complexity,
> > reliability, maintainability of trying to interlock WAL application with
> > slave queries in any sort of fine-grained fashion.
> 
> Some admin functions for Hot Standby were removed from the path to ease
> its integration, there was a pause() and resume() feature.
> 
> I think that offering this explicit control to the user would allow them
> to choose between HA setup and reporting setup easily enough: just pause
> the replay when running the reporting, resume it to get fresh data
> again. If you don't pause, any query can get killed, replay is the
> priority.

Doesn't the system already adjust the delay based on the length of slave
transactions, e.g. max_standby_delay.  It seems there is no need for a
user switch --- just max_standby_delay really high.

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