private List<Object> project(Map<String, String> fieldToTableMap, List<String> fields,
                               List<Map<String, ? extends Element>> results,
                               Map<String, TableDef> tableIdToTableDefMap) {
    final List<Object> rows = new ArrayList<>(results.size());
    Map<String, String> labelTableIdMap = new HashMap<>();
    for (Map.Entry<String, TableDef> entry : tableIdToTableDefMap.entrySet()) {
        labelTableIdMap.put(entry.getValue().label.toLowerCase(), entry.getKey());
    }
    for(Map<String, ? extends Element> result : results) {
        final Object[] row = new Object[fields.size()];
        int column = 0;
        for(String field : fields) {
            String tableId = fieldToTableMap.get(field);
            String simpleFieldName = Character.isDigit(field.charAt(field.length()-1)) ?
                    field.substring(0, field.length()-1) : field;
            simpleFieldName = Character.isDigit(field.charAt(simpleFieldName.length()-1)) ?
                    simpleFieldName.substring(0, simpleFieldName.length()-1) : simpleFieldName;
            // check for primary & fks
            final int keyIndex = simpleFieldName.toLowerCase().indexOf("_id");
            Object val = null;
            if(keyIndex > 0) {
                // is it a pk or fk?
                String key = simpleFieldName.substring(0, keyIndex);
                String tableLabel = tableIdToTableDefMap.get(tableId).label;
                if(tableLabel.toLowerCase().equals(key.toLowerCase())) {
                    val = result.get(tableId).id();
                } else {
                    String fkTableId = labelTableIdMap.get(key.toLowerCase());
                    if(result.containsKey(fkTableId)) {
                        val = result.get(fkTableId).id();
                    }
                }
            }
            final Property<Object> property = result.get(tableId).
                    property(tableIdToTableDefMap.get(tableId).getColumn(simpleFieldName.toLowerCase()).getPropertyName());
            if(!(property instanceof EmptyProperty || property instanceof EmptyVertexProperty)) {
                if(result.get(tableId).label().equals(tableIdToTableDefMap.get(tableId).label)) {
                    val = property.value();
                } else {
                    val = null;
                }
            }
            if(tableIdToTableDefMap.get(tableId).getColumn(field) != null && val != null) {
                row[column++] = TableUtil.convertType(val, tableIdToTableDefMap.get(tableId).getColumn(field));
            } else {
                row[column++] = val;
            }
        }
        rows.add(row);
    }
    return rows;
}
 

/**
 * Constructs an empty {@code VertexProperty}.
 */
public static <V> VertexProperty<V> empty() {
    return EmptyVertexProperty.instance();
}