code: public void setPartitionFilter(Expression partitionFilter) throws IOException
      {
          UDFContext context = UDFContext.getUDFContext();
          Properties property = context.getUDFProperties(AbstractCassandraStorage.class);
          property.setProperty(PARTITION_FILTER_SIGNATURE, indexExpressionsToString(filterToIndexExpressions(partitionFilter)));
      }
docs: set partition filter