lonvia left a comment (osm2pgsql-dev/osm2pgsql#1323)
We've removed the statistics in question in the meantime as its usefulness was
limited in general. So I'm going to close this issue.
> The difference between a db access for 1 node vs 10 nodes is low, but 0 nodes
> vs 1 nodes is large. Effectively this means a 90% hit rate is a 0% hit rate,
> making the stats less meaningful.
This observation is correct, when node locations are stored in the database. If
you are using flat node store, then the coast of cache miss is directly
proportional to the number of missed nodes.
The numbers you computed might be indeed interesting from a developer point of
view to make decisions on what are good defaults. For users the only really
interesting number would be the percentage of nodes that could be stored in the
cache. The hit/miss rate will be very closely tidy to that. Eventually, if will
be easier for users to just follow the [advice on cache
size](https://osm2pgsql.org/doc/manual.html#caching) in the manual, than
looking at the cache usage statistics. That's why we dropped the stats when
renovating the code.
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