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
