FYI:
To solve the performance problems on lower zoom level, I modify
expire.rb a little bit so that we have now no fix MIN_ZOOM value.
Instead the MIN_ZOOM is changing with definable probabilities. [1]
(Expiring works on zoomlevel MIN_ZOOM to MAX_ZOOM).
Low zoom-levels cost us a lot and changes are often not visible.
So edits on OSM leads to expirings on higher zoom-level with a higher
probability than on low levels. Areas with high mapping activities will
re-render more often than death areas.
Z16-18 will expire each time. z10 will only expire with a probability of
1.5%. We can adjust this values each time.
I hope this help us if we restart the updating of the db, where this
script works.
[1]
random= rand()
prob=[0,0,0,0,0,0,0,0,0,0.00625,0.0125,0.025,0.05,0.1,0.2,0.4,1,1,1]
#probability for each zoomlevel to expire
z = 18
while z > 0
if random<prob[z]
mini=z
end
z -= 1
end
MIN_ZOOM=mini