>
> > So, if anybody reads from sl_log_status, it blocks until anything is
> written
> > to sl_log_status. Seems it will be fully transparent for Slony, but
> > decreases the amount of polling queries. (It is an idea only, practical
> > implementation may need to be more detailed.) What do you think about
> it?
>
> It sounds like a way to make everything a lot slower.


Why? Where is the slowdown?

It reduces the number of polling queries without affecting the speed of a
slave reaction... And does not affect pg_listeners, so - there is no problem
with pg_listeners vacuuming. Where am I wrong?

One way you could improve your notification about whether a slave is
> up to date enough for you is to add a sequence.  When you start your
> transaction, you select nextval() from the sequence.

I think "select last_value from "_moikrug_cluster".sl_log_status" query may
also be used to check if the slave is "up to date enough". But it is not the
main problem - slave checking. The main problem for me is to reduce the
number of polling queries without increasing the slave lag time.
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