def test_node_deletion(self):
io = Io()
value = "Graph DB is AWESOME"
label = Label(cfg.INV_ID, value)
prop_value = True
property = Property(cfg.INV_ID, PropertyType.BOOL, label, prop_value,
None)
node = Node(cfg.INV_ID, label, property, cfg.INV_ID)
written = io.write_node(node)
io.del_node(written.id)
retrieved = io.get_nodes_by_id([written.id])
self.assertEqual(len(retrieved), 0)
def test_multirelation_deletion(self):
io = Io()
value = "You spin my head right ground right ground"
label = Label(cfg.INV_ID, value)
label = io.write_label(label)
prop_value = True
property = Property(cfg.INV_ID, PropertyType.BOOL, label, prop_value,
None)
property = io.write_property(property)
node = Node(cfg.INV_ID, label, property, None)
node2 = Node(cfg.INV_ID, label, property, None)
written_node1 = io.write_node(node)
written_node2 = io.write_node(node2)
relation1 = Relationship(cfg.INV_ID, False, written_node1,
written_node2, label, property, None, None,
None, None)
relation2 = Relationship(cfg.INV_ID, False, written_node1,
written_node2, label, property, None, None,
None, None)
written_rel1 = io.write_relation(relation1)
written_rel2 = io.write_relation(relation2)
io.del_node(written_node1.id)
retrived = io.get_relations_by_id([written_rel1.id, written_rel2.id])
self.assertEqual(len(retrived), 0)
class GraphEngine:
"""
The graph database engine that performs operations on data stored in the database.
Attributes:
_lb_cache (dict): A label cache that contains all labels in the graph database.
Has the following format:
{'label.value': 'label'}.
_index (dict): An index that improves the speed of data retrieval. Is built on label and at least one property.
Has the following format:
{'node.label.id': '{'(node.next_prop.label.id, ...)': '{'(node.next_prop.value, ...)': '(node.id, ...)'}'}'}
"""
def __init__(self):
self._io = Io()
self._lb_cache = self._init_lb_cache()
self._index = dict()
def _init_lb_cache(self):
"""
Initializes the label cache.
:return: Dictionary which has the following format:
{'label.value': 'label'}.
"""
lb_cache = dict()
for label in self._io.get_labels_by_id(set()):
lb_cache[label.value] = label
return lb_cache
def create_node(self, node):
"""
Creates the new node.
:param node: A pair (<label>, <properties>) corresponding to a node.
:return: Void
"""
label, next_prop = node
# Before write to the storage dedupe the labels
label = self._dedupe_label(label)
next_prop = self._dedupe_next_prop(next_prop)
created_node = self._io.write_node(Node(cfg.INV_ID, label, next_prop))
label, next_prop = created_node.label, created_node.next_prop
# Add new labels to the corresponding cache
self._lb_cache[label.value] = label
while next_prop is not None:
self._lb_cache[next_prop.label] = next_prop.label
next_prop = next_prop.next_prop
# Update index (if any)
if len(self._index) != 0:
lookup = self._index_lookup((label, next_prop))
for key, value in lookup.values():
if value not in self._index[label.id][key]:
self._index[label.id][key][value] = list()
self._index[label.id][key][value].append(created_node.id)
def create_relationship(self, first_node, second_node, relationship):
"""
Creates new relationships between nodes that match 'first_node' and 'second_node'.
:param first_node: A pair (<label>, <properties>) corresponding to the node at the start of a relationship.
:param second_node: A pair (<label>, <properties>) corresponding to the node at the end of a relationship.
:param relationship: A triplet (<label>, <properties>, <direction>) corresponding to a relationship.
:return: Void
"""
label, next_prop, direction = relationship
label = self._dedupe_label(label)
next_prop = self._dedupe_next_prop(next_prop)
is_directed = False
if direction == 1:
is_directed = True
elif direction == -1:
is_directed = True
first_node, second_node = second_node, first_node
retrieved_first_node = self._retrieve_node(first_node)
retrieved_second_node = self._retrieve_node(second_node)
for first in retrieved_first_node:
for second in retrieved_second_node:
created_relationship = self._io.write_relation(
Relationship(cfg.INV_ID, is_directed, first, second, label,
next_prop, None, None, None, None))
label, next_prop = created_relationship.label, created_relationship.next_prop
# Add new labels to the corresponding cache
self._lb_cache[label.value] = label
while next_prop is not None:
self._lb_cache[next_prop.label] = next_prop.label
next_prop = next_prop.next_prop
def create_index(self, node):
"""
Creates index on nodes that have label and properties in accordance with the provided template.
:param node: A pair (<label>, <properties>) corresponding to the template based on which index will be created.
:return: Void
"""
label, next_prop = node
label = self._dedupe_label(label)
next_prop = self._dedupe_next_prop(next_prop)
key_property = tuple(self._unroll_next_prop(next_prop).keys())
retrieved_node = self._retrieve_node((label, next_prop))
if label.id not in self._index:
self._index[label.id] = dict()
self._index[label.id][key_property] = dict()
for ind_node in retrieved_node:
properties = self._unroll_next_prop(ind_node.next_prop)
key_value = list()
for k in key_property:
key_value.append(properties[k])
key_value = tuple(key_value)
if key_value not in self._index[label.id][key_property]:
self._index[label.id][key_property][key_value] = list()
self._index[label.id][key_property][key_value].append(ind_node.id)
def delete_node(self, node):
"""
Deletes all nodes that match 'node'.
:param node: A pair (<label>, <properties>) corresponding to a node.
:return: Void
"""
retrieved_node = self._retrieve_node(node)
for ind_node in retrieved_node:
self._io.del_node(ind_node.id)
def delete_relationship(self, first_node, second_node, relationship):
"""
Deletes all relationships that match 'relationship' between nodes that match 'first_node' and 'second_node'.
:param first_node: A pair (<label>, <properties>) corresponding to the node at the start of a relationship.
:param second_node: A pair (<label>, <properties>) corresponding to the node at the end of a relationship.
:param relationship: A triplet (<label>, <properties>, <direction>) corresponding to a relationship.
:return: Void
"""
retrieved_relationship = self._retrieve_relationship(
first_node, second_node, relationship)
for ind_relationship_id in [
relationship_id
for _, _, relationship_id in retrieved_relationship
]:
self._io.del_relation(ind_relationship_id)
def match_pattern(self, nodes, relationships):
"""
Matches the pattern that contain several nodes and relationships connecting them.
:param nodes: List of pairs (<label>, <properties>) for each node.
:param relationships: List of triplets (<label>, <properties>, <direction>) for each relation.
Must be provided if 'nodes' contain more than one node.
:return: Dictionary which has the following format:
{'idx of the obj': 'nodes'}
"""
retrieved_node = dict()
if len(nodes) == 1:
retrieved_node[0] = self._retrieve_node(nodes.pop())
else:
iterator = iter(nodes)
for nodes, relationship in zip(zip(iterator, iterator),
relationships):
# For now assume that this chain contains only one relationship
first_node, second_node = nodes
retrieved_relationship = self._retrieve_relationship(
first_node, second_node, relationship)
retrieved_node[0] = [
first_node for first_node, _, _ in retrieved_relationship
]
retrieved_node[1] = [
second_node for _, second_node, _ in retrieved_relationship
]
return retrieved_node
def _index_lookup(self, node):
"""
Finds the pointer to the index record corresponding to a node.
:param node: A pair (<label>, <properties>) corresponding to a node.
:return: Dictionary which has the following format:
{'(node.next_prop.label.id, ...)': '(node.next_prop.value, ...)'}
"""
label, next_prop = node
conformity = dict()
while next_prop is not None:
if label.id in self._index:
keys = self._index[label.id].keys()
for key in keys:
if next_prop.label.id in key:
if key not in conformity:
conformity[key] = dict()
conformity[key][next_prop.label.id] = next_prop.value
next_prop = next_prop.next_prop
result = dict()
for key, value in conformity.items():
keys = value.keys()
if set(key) == set(keys):
result[key] = tuple([value[k] for k in list(key)])
return result
def _retrieve_relationship(self, first_node, second_node, relationship):
"""
Retrieves all relationships that match 'relationship' between nodes that match 'first_node' and 'second_node'.
:param first_node: A pair (<label>, <properties>) corresponding to the node at the start of a relationship OR
list of already retrieved nodes.
:param second_node: A pair (<label>, <properties>) corresponding to the node at the end of a relationship OR
list of already retrieved nodes.
:param relationship: A triplet (<label>, <properties>, <direction>) corresponding to a relationship.
:return: List of triplets (<first_node>, <second_node>, <relationship_id>).
"""
label, next_prop, direction = relationship
label = self._dedupe_label(label)
next_prop = self._dedupe_next_prop(next_prop)
rel_properties = self._unroll_next_prop(next_prop)
is_directed = False
if direction == 1:
is_directed = True
elif direction == -1:
is_directed = True
first_node, second_node = second_node, first_node
retrieved_first_node = dict()
if type(first_node) is tuple:
for first in self._retrieve_node(first_node):
retrieved_first_node[first.id] = first
else:
for first in first_node:
retrieved_first_node[first.id] = first
second_label = second_next_prop = second_properties = None
retrieved_second_node = dict()
if type(second_node) is tuple:
second_label, second_next_prop = second_node
second_label = self._dedupe_label(second_label)
second_next_prop = self._dedupe_next_prop(second_next_prop)
second_properties = self._unroll_next_prop(second_next_prop)
else:
for second in second_node:
retrieved_second_node[second.id] = second
retrieved_relationship = list()
for _, first in retrieved_first_node.items():
first_next_rel = first.next_rel
while first_next_rel is not None:
if type(first_next_rel) is not Relationship:
first_next_rel = self._io.read_relation(first_next_rel)
appropriate = first_next_rel.label.id == label.id
appropriate = appropriate and (
(is_directed and
(not first_next_rel.is_directed
or first_next_rel.first_node == first.id)) or
(not is_directed and not first_next_rel.is_directed))
first_next_rel_properties = self._unroll_next_prop(
first_next_rel.next_prop)
appropriate = appropriate and (
first_next_rel.next_prop is None or
(first_next_rel_properties is not None
and all(first_next_rel_properties[k] == v
for k, v in rel_properties.items())))
if appropriate:
second = None
if len(retrieved_second_node) != 0:
if first_next_rel.second_node in retrieved_second_node:
second = retrieved_second_node[
first_next_rel.second_node]
else:
second = self._io.read_node(
first_next_rel.second_node.id)
retrieved_second_properties = self._unroll_next_prop(
second.next_prop)
if second.label.id != second_label.id or (not (
second_next_prop is None or
(retrieved_second_properties is not None
and all(retrieved_second_properties[k] == v
for k, v in second_properties.items())))):
second = None
if second is not None:
retrieved_relationship.append(
(first, second, first_next_rel.id))
first_next_rel = first_next_rel.first_next_rel
return retrieved_relationship
def _retrieve_node(self, node):
"""
Retrieves all nodes that match 'node' from the persistent storage.
:param node: A pair (<label>, <properties>) corresponding to a node.
:return: List of all nodes that match 'node'.
"""
label, next_prop = node
label = self._dedupe_label(label)
next_prop = self._dedupe_next_prop(next_prop)
nodes_to_retrieve = set()
# Perform lookup to find indexes
if len(self._index) != 0:
lookup = self._index_lookup(node)
if len(lookup) != 0:
key, value = lookup.popitem()
nodes_to_retrieve = self._index[label.id][key][value]
if not nodes_to_retrieve:
return list()
retrieved_nodes = self._io.get_nodes_by_id(nodes_to_retrieve)
# Filter the retrieved nodes
node_properties = self._unroll_next_prop(next_prop)
filtered_retrieved_nodes = list()
for retrieved_node in retrieved_nodes:
if retrieved_node.label.id == label.id:
retrieved_node_properties = self._unroll_next_prop(
retrieved_node.next_prop)
if next_prop is None or (
retrieved_node_properties is not None
and all(retrieved_node_properties[k] == v if k in
retrieved_node_properties else False
for k, v in node_properties.items())):
filtered_retrieved_nodes.append(retrieved_node)
return filtered_retrieved_nodes
@staticmethod
def _unroll_next_prop(next_prop):
"""
Unrolls the chain of properties starting from the provided link 'next_prop'.
:param next_prop: The first link in the chain which should be be unrolled.
:return: Dictionary which has the following format:
{'next_prop.label.id': 'next_prop.value'}
"""
properties = dict()
while next_prop is not None:
properties[next_prop.label.id] = next_prop.value
next_prop = next_prop.next_prop
return properties
def _dedupe_next_prop(self, next_prop):
"""
Resolves duplicate labels of each property in the chain starting from 'next_prop'.
:param next_prop: The first property in the chain the labels of which should be be deduped.
:return: Property.
"""
saved_pointer = next_prop
while next_prop is not None:
next_prop.label = self._dedupe_label(next_prop.label)
next_prop = next_prop.next_prop
return saved_pointer
def _dedupe_label(self, label):
"""
Resolves duplicate labels.
:param label: A label to be deduped.
:return: Label.
"""
return self._lb_cache[
label.value] if label.value in self._lb_cache else label