presto-raptor-legacy/src/main/java/io/prestosql/plugin/raptor/legacy/metadata/DatabaseShardManager.java/DatabaseShardManager/toNodeIdMap
class DatabaseShardManager:    private Map<String, Integer> toNodeIdMap(Collection<ShardInfo> shards)
    {
        Set<String> identifiers = shards.stream()
                .map(ShardInfo::getNodeIdentifiers)
                .flatMap(Collection::stream)
                .collect(toSet());
        return Maps.toMap(identifiers, this::getOrCreateNodeId);
    }