there's this line

TODO: Use LMDB database statistics when lmdb-rs exposes them.

in the local store source above the

shrink()

method: https://github.com/pantsbuild/pants/blob/237e6a6e8b1c41d58a38426d92dac96f878f2159/src/rust/engine/fs/store/src/local.rs#L121, and in looking over that i found this

environment::Stat

object from the upstream lmdb-rs crate: https://github.com/danburkert/lmdb-rs/blob/12b4611006d5ba3bf80840faaa31a8b2e2bb6e88/src/environment.rs#L171. it's described as

Contains information about the size and layout of an LMDB environment.

. is that the info we would be looking for here?