public GroupedVectorStore() throws IOException { super(new NullOutputFormat()); Env.inBackground( new Env.BackgroundProcedure() { @Override public void execute(Configuration conf) throws IOException { tvgen = VectorUtils.createVectorGenerator( Env.getProperty(GroupedVectorStore.class, "vector.type")); writers = new HashMap<Object, SequenceFile.Writer>(); keyWritable = new IntWritable(); valueWritable = new VectorWritable(); } }); }