@Override
  public List<String> getFieldNames() {
    if (formatJson) {
      return Collections.singletonList("metadata");
    }
    return Arrays.asList(NUM_SNAPSHOTS, NUM_METADATA_FILES, NUM_MANIFESTS,
        MANIFESTS_SIZE, SNAPSHOT_MAX_AGE, SNAPSHOT_MIN_KEEP, NUM_BRANCHES, NUM_TAGS);
  }
Collect the metadata summary for the table, like the number of snapshots, data files
or the partition count.
iceberg/iceberg-handler/src/main/java/org/apache/iceberg/metasummary/MetadataSummary.java