presto-main/src/main/java/io/prestosql/operator/SpilledLookupSourceHandle.java/SpilledLookupSourceHandle/setLookupSource
class SpilledLookupSourceHandle:    public synchronized void setLookupSource(Supplier<LookupSource> lookupSource)
    {
        requireNonNull(lookupSource, "lookupSource is null");

        if (state == State.DISPOSED) {
            return;
        }

        assertState(State.UNSPILLING);
        checkState(unspilledLookupSource != null, "unspilledLookupSource not set");
        unspilledLookupSource.set(lookupSource);
        unspilledLookupSource = null; // let the memory go
        setState(State.PRODUCED);
    }