presto-main/src/main/java/io/prestosql/operator/PartitionedLookupSourceFactory.java/PartitionedLookupSourceFactory/closeCachedLookupSources
class PartitionedLookupSourceFactory:    private void closeCachedLookupSources()
    {
        lock.writeLock().lock();
        try {
            suppliedLookupSources.values().forEach(LookupSource::close);
            suppliedLookupSources.clear();
        }
        finally {
            lock.writeLock().unlock();
        }
    }