Greg Smith <g...@2ndquadrant.com> writes:
> If the standby is not current, you may not want people to execute 
> queries against it.  In some situations, returning results against 
> obsolete data is worse than not letting the query execute at all.  As I 
> see it, the current max_standby_delay implementation includes the 
> expectation that the results you are getting are no more than 
> max_standby_delay behind the master, presuming that new data is still 
> coming in.  If the standby has really fallen further behind than that, 
> there are situations where you don't want it doing anything but catching 
> up until that is no longer the case, and you especially don't want it 
> returning stale query data.

That is very possibly a useful thing to be able to specify, but the
current implementation has *nothing whatsoever* to do with making such a
guarantee.  It will only kill queries that are creating a lock conflict.
I would even argue that it's a bad thing to have a parameter that looks
like it might do that, when it doesn't.

                        regards, tom lane

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