chronicle-map persisted file size

Question

I am trying to understand how the size of persisted map files is calculated.

When creating a persisted map on disk via something like:

ChronicleMap
   .of(Key.class, Value.class)
   .name("foo")
   .entries(1024)
   .averageKeySize(32)
   .averageValueSize(2048)
   .maxBloatFactor(1)
   .createOrRecoverPersistedTo("foo.dat")

I imagine the size of the pre-allocated "foo.dat" file is a function of key/value size, the number of entries and maxBloatFactor, and perhaps OS architecture and other factors.

So my question is: Given a set of configuration values, is it possible to know deterministically how much the "foo.dat" file size will end up being?

Answer 1

You can simply call the VanillaChronicleMap#dataStoreSize() method, it will return the file size.

For details on how it works you can have a look at its implementation - it's opensource (albeit it's not a trivial computation).