Since all the DB libraries are imported from a single package, using a single one of them requires building all of them. And since each is registered globally, they must be bundled in the final binary too.

This will get worse as more DB implementations are added (#38). I made a write-up about this, and potential solutions, on ChainSafe/chaindb#2 since that module has a similar issue.

Similarly, I think a database implementation called foo should live at github.com/tendermint/tm-db/foo. Then, to use it, one would need to call a constructor like foo.New(...) instead of db.NewDB("foo", ...). This way, because the user only imports the database implementations they need, Go only builds and links the libraries as needed, not all of them at once.