presto-hive/src/main/java/io/prestosql/plugin/hive/metastore/file/FileHiveMetastore.java/FileHiveMetastore/dropDatabase
class FileHiveMetastore:    @Override
    public synchronized void dropDatabase(HiveIdentity identity, String databaseName)
    {
        requireNonNull(databaseName, "databaseName is null");

        getRequiredDatabase(databaseName);
        if (!getAllTables(databaseName).isEmpty()) {
            throw new PrestoException(HIVE_METASTORE_ERROR, "Database " + databaseName + " is not empty");
        }

        deleteMetadataDirectory(getDatabaseMetadataDirectory(databaseName));
    }