presto-main/src/main/java/io/prestosql/operator/SpilledLookupSourceHandle.java/SpilledLookupSourceHandle/dispose
class SpilledLookupSourceHandle:    public synchronized void dispose()
    {
        disposeRequested.set(null);
        unspilledLookupSource = null; // let the memory go
        setState(State.DISPOSED);
    }