presto-hive/src/main/java/io/prestosql/plugin/hive/metastore/cache/CachingHiveMetastore.java/CachingHiveMetastore/getPartitionStatistics
class CachingHiveMetastore:    @Override
    public Map<String, PartitionStatistics> getPartitionStatistics(HiveIdentity identity, String databaseName, String tableName, Set<String> partitionNames)
    {
        HiveTableName hiveTableName = hiveTableName(databaseName, tableName);
        List<WithIdentity<HivePartitionName>> partitions = partitionNames.stream()
                .map(partitionName -> new WithIdentity<>(updateIdentity(identity), hivePartitionName(hiveTableName, partitionName)))
                .collect(toImmutableList());
        Map<WithIdentity<HivePartitionName>, PartitionStatistics> statistics = getAll(partitionStatisticsCache, partitions);
        return statistics.entrySet()
                .stream()
                .collect(toImmutableMap(entry -> entry.getKey().getKey().getPartitionName().get(), Entry::getValue));
    }