[DISCUSS] FileStore doesn't seem to scale that well becauser of precomputed graph on TarReader

[Andrei Dulvac]

Hi guys,

I created OAK-2723 to track an issue regarding FileStore.

I tried running the tar compaction via oak-run, but I had a HeapSpace
exception immediately when trying to instantiate the object, with 6GB of
allocated memory:

FileStore store = new FileStore(directory, 256, TAR_STORAGE_MEMORY_MAPPED);

There's an unnecessary reference to all the precomputed "tar graphs" in
TarReader, which causes this issue, for what I consider "a realistic" repo
size - 350GB.

Can somebody pick this up and review? I tested it only in the context of
oak-run compaction.

Thank you!
- Andrei