def save_relationship(self, entity, ensure_unique=False): """this method handles creating and saving relationships. It will hanle quite a few situations. Given the structure: (start)-[rel]->[end] We can have: * A new start node * An existing start node * A new rel * An existing rel * A new end node * An existing end node Each start, rel, and end could have uniqueness assigned to it * start/end could have unique properties * rel could have unique relationships A Chyper query should be generated that looks something like this, depending on the settings for each of the nodes: MERGE (n_0:Node {`key`: val}) ON CREATE SET n_0.key = val, n_0.key2 = val2 ON MATCH SET n_0.key = val, n_0.key2 = val2 CREATE (n_0)-[r_0:RelLabel, {`key`: someVal}]->(n_1:Node {`key`: val}) RETURN n_0, n_1, r_0 """ start = entity.start start_properties = {} end = entity.end end_properties = {} props = self._properties(entity) if start is None or end is None: raise Exception('The relationship must have a start and end node') if not isinstance(start, Node): start = Node(id=start) if not isinstance(end, Node): end = Node(id=end) VM.set_query_var(start) VM.set_query_var(end) VM.set_query_var(entity) rel = Pypher() if start not in self.matched_entities: if start.id is not None: self._update_properties(start) self.matches.append(self._node_by_id(start)) else: start_properties = self._properties(start) self.matched_entities.append(start) self.returns.append(start.query_variable) if end not in self.matched_entities: if end.id is not None: self._update_properties(end) self.matches.append(self._node_by_id(end)) else: end_properties = self._properties(end) self.matched_entities.append(end) self.returns.append(end.query_variable) if entity.id is None: if start.id is not None: rel = rel.node(start.query_variable) else: start_query = Query(start, self.params) start_query.build_save_pypher() if len(start_query.creates): rel.append(*start_query.creates) elif len(start_query.merges): has_matches = len(self.matches) > 0 start_merge = Pypher() start_merge.MERGE(*start_query.merges) if start_query.on_create_sets: start_merge.OnCreateSet(*start_query.on_create_sets) if start_query.on_match_sets: start_merge.OnMatchSet(*start_query.on_match_sets) self.before_matches.append(start_merge) rel.node(start.query_variable) rel.rel(entity.query_variable, labels=entity.labels, direction='out', **props) if end.id is not None: rel.node(end.query_variable) else: end_query = Query(end, self.params) end_query.build_save_pypher() if len(end_query.creates): rel.append(*end_query.creates) elif len(end_query.merges): end_merge = Pypher().MERGE(*end_query.merges) if end_query.on_create_sets: end_merge.OnCreateSet(*end_query.on_create_sets) if end_query.on_match_sets: end_merge.OnMatchSet(*end_query.on_match_sets) self.before_matches.append(end_merge) rel.node(end.query_variable) if ensure_unique: self.merges.append(rel) else: self.creates.append(rel) else: _id = VM.get_next(entity, 'id') _id = Param(_id, entity.id) if start.id is not None: rel = rel.node(start.query_variable) else: start_query = Query(start, self.params) start_query.build_save_pypher() if len(start_query.creates): rel.append(*start_query.creates) elif len(start_query.merges): start_merge = Pypher().MERGE(*start_query.merges) if start_query.on_create_sets: start_merge.OnCreateSet(*start_query.on_create_sets) if start_query.on_match_sets: start_merge.OnMatchSet(*start_query.on_match_sets) if len(self.matches): self.matches[-1].append(start_merge) else: self.matches.append(start_merge) rel.node(start.query_variable) rel.rel(entity.query_variable, labels=entity.labels, direction='out') if end.id is not None: rel.node(end.query_variable) else: end_query = Query(end, self.params) end_query.build_save_pypher() if len(end_query.creates): rel.append(*end_query.creates) elif len(end_query.merges): end_merge = Pypher().MERGE(*end_query.merges) if end_query.on_create_sets: end_merge.OnCreateSet(*end_query.on_create_sets) if end_query.on_match_sets: end_merge.OnMatchSet(*end_query.on_match_sets) if len(self.matches): self.matches[-1].append(end_merge) else: self.matches.append(end_merge) rel.node(end.query_variable) rel.WHERE(__.ID(entity.query_variable) == _id) self._update_properties(entity) self.matches.append(rel) self.returns.append(entity.query_variable) return self