#!/usr/bin/env python
# -*- encoding: utf-8 -*-
# Copyright 2011-2021, Nigel Small
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
from __future__ import absolute_import, print_function
__all__ = [
"GraphService",
"Graph",
"SystemGraph",
"Schema",
"Transaction",
]
from inspect import isgenerator
from time import sleep
from py2neo.compat import (deprecated,
Sequence,
Mapping)
from py2neo.cypher import Cursor, cypher_escape
from py2neo.cypher.proc import ProcedureLibrary
from py2neo.errors import (Neo4jError,
ConnectionUnavailable,
ConnectionBroken,
ConnectionLimit,
ServiceUnavailable,
WriteServiceUnavailable)
from py2neo.matching import NodeMatcher, RelationshipMatcher
[docs]class GraphService(object):
""" The :class:`.GraphService` class is the top-level accessor for
an entire Neo4j graph database management system (DBMS). Within the
py2neo object hierarchy, a :class:`.GraphService` contains one or
more :class:`.Graph` objects in which data storage and retrieval
activity chiefly occurs.
An explicit URI can be passed to the constructor::
>>> from py2neo import GraphService
>>> gs = GraphService("bolt://camelot.example.com:7687")
Alternatively, the default value of ``bolt://localhost:7687`` is
used::
>>> default_gs = GraphService()
>>> default_gs
<GraphService uri='bolt://localhost:7687'>
.. note::
Some attributes of this class available in earlier versions of
py2neo are no longer available, specifically
``kernel_start_time``, ``primitive_counts``,
``store_creation_time``, ``store_file_sizes`` and ``store_id``,
along with the ``query_jmx`` method. This is due to a change in
Neo4j 4.0 relating to how certain system metadata is exposed.
Replacement functionality may be reintroduced in a future
py2neo release.
*Changed in 2020.0: this class was formerly known as 'Database',
but was renamed to avoid confusion with the concept of the same
name introduced with the multi-database feature of Neo4j 4.0.*
.. describe:: iter(graph_service)
Yield all named graphs.
For Neo4j 4.0 and above, this yields the names returned by a
``SHOW DATABASES`` query. For earlier versions, this yields no
entries, since the one and only graph in these versions is not
named.
*New in version 2020.0.*
.. describe:: graph_service[name]
Access a :class:`.Graph` by name.
*New in version 2020.0.*
"""
_connector = None
_graphs = None
def __init__(self, profile=None, **settings):
from py2neo import ServiceProfile
from py2neo.client import Connector
connector_settings = {
"user_agent": settings.pop("user_agent", None),
"init_size": settings.pop("init_size", None),
"max_size": settings.pop("max_size", None),
"max_age": settings.pop("max_age", None),
"routing_refresh_ttl": settings.pop("routing_refresh_ttl", None),
}
profile = ServiceProfile(profile, **settings)
if connector_settings["init_size"] is None and not profile.routing:
# Ensures credentials are checked on construction
connector_settings["init_size"] = 1
self._connector = Connector(profile, **connector_settings)
self._graphs = {}
def __repr__(self):
class_name = self.__class__.__name__
profile = self._connector.profile
return "<%s uri=%r secure=%r user_agent=%r>" % (
class_name, profile.uri, profile.secure, self._connector.user_agent)
def __eq__(self, other):
try:
return self.uri == other.uri
except AttributeError:
return False
def __ne__(self, other):
return not self.__eq__(other)
def __hash__(self):
return hash(self._connector)
def __getitem__(self, graph_name):
if graph_name is None:
graph_name = self._connector.default_graph_name()
elif graph_name not in self._connector.graph_names():
raise KeyError("Graph {!r} does not exist for "
"service {!r}".format(graph_name, self._connector.profile.uri))
if graph_name not in self._graphs:
graph_class = SystemGraph if graph_name == "system" else Graph
self._graphs[graph_name] = graph_class(self.profile, name=graph_name)
return self._graphs[graph_name]
def __iter__(self):
return iter(self._connector.graph_names())
@property
def connector(self):
""" The :class:`.Connector` providing communication for this
graph service.
*New in version 2020.0.*
"""
return self._connector
@property
def profile(self):
""" The :class:`.ConnectionProfile` for which this graph
service is configured. This attribute is simply a shortcut
for ``connector.profile``.
*New in version 2020.0.*
"""
return self.connector.profile
@property
def uri(self):
""" The URI to which this graph service is connected. This
attribute is simply a shortcut for ``connector.profile.uri``.
"""
return self.profile.uri
@property
def default_graph(self):
""" The default :class:`.Graph` exposed by this graph service.
"""
return self[None]
@property
def system_graph(self):
""" The :class:`.SystemGraph` exposed by this graph service.
*New in version 2020.0.*
"""
return self["system"]
[docs] def keys(self):
""" Return a list of all :class:`.Graph` names exposed by this
graph service.
*New in version 2020.0.*
"""
return list(self)
@property
def kernel_version(self):
""" The :class:`~packaging.version.Version` of Neo4j running.
"""
from packaging.version import Version
components = self.default_graph.call("dbms.components").data()
kernel_component = [component for component in components
if component["name"] == "Neo4j Kernel"][0]
version_string = kernel_component["versions"][0]
return Version(version_string)
@property
def product(self):
""" The product name.
"""
record = next(self.default_graph.call("dbms.components"))
return "%s %s (%s)" % (record[0], " ".join(record[1]), record[2].title())
@property
def config(self):
""" A dictionary of the configuration parameters used to
configure Neo4j.
>>> gs.config['dbms.connectors.default_advertised_address']
'localhost'
"""
return {record["name"]: record["value"]
for record in self.default_graph.call("dbms.listConfig")}
[docs]class Graph(object):
""" The `Graph` class provides a handle to an individual named
graph database exposed by a Neo4j graph database service.
Connection details are provided using either a URI or a
:class:`.ConnectionProfile`, plus individual settings, if required.
The `name` argument allows selection of a graph database by name.
When working with Neo4j 4.0 and above, this can be any name defined
in the system catalogue, a full list of which can be obtained
through the Cypher ``SHOW DATABASES`` command. Passing `None` here
will select the default database, as defined on the server. For
earlier versions of Neo4j, the `name` must be set to `None`.
>>> from py2neo import Graph
>>> sales = Graph("bolt+s://g.example.com:7687", name="sales")
>>> sales.run("MATCH (c:Customer) RETURN c.name")
c.name
---------------
John Smith
Amy Pond
Rory Williams
The `system graph`, which is available in all 4.x+ product editions,
can also be accessed via the :class:`.SystemGraph` class.
>>> from py2neo import SystemGraph
>>> sg = SystemGraph("bolt+s://g.example.com:7687")
>>> sg.call("dbms.security.listUsers")
username | roles | flags
----------|-------|-------
neo4j | null | []
In addition to the core `connection details <#getting-connected>`_
that can be passed to the constructor, the :class:`.Graph` class
can accept several other settings:
=================== ======================================================== ============== =========================
Keyword Description Type Default
=================== ======================================================== ============== =========================
``user_agent`` User agent to send for all connections str `(depends on URI scheme)`
``max_connections`` The maximum number of simultaneous connections permitted int 40
=================== ======================================================== ============== =========================
Once obtained, the `Graph` instance provides direct or indirect
access to most of the functionality available within py2neo.
"""
#: The :class:`.GraphService` to which this :class:`.Graph` belongs.
service = None
#: The :class:`.Schema` resource for this :class:`.Graph`.
schema = None
def __init__(self, profile=None, name=None, **settings):
self.service = GraphService(profile, **settings)
self.__name__ = name
self.schema = Schema(self)
self._procedures = ProcedureLibrary(self)
def __repr__(self):
if self.name is None:
return "%s(%r)" % (self.__class__.__name__, self.service.uri)
else:
return "%s(%r, name=%r)" % (self.__class__.__name__, self.service.uri, self.name)
def __eq__(self, other):
try:
return self.service == other.service and self.__name__ == other.__name__
except (AttributeError, TypeError):
return False
def __ne__(self, other):
return not self.__eq__(other)
def __len__(self):
return len(self.relationships)
def __bool__(self):
return True
__nonzero__ = __bool__
@property
def name(self):
""" The name of this graph.
*New in version 2020.0.*
"""
return self.__name__
# TRANSACTION MANAGEMENT #
[docs] def auto(self, readonly=False,
# after=None, metadata=None, timeout=None
):
""" Create a new auto-commit :class:`~py2neo.Transaction`.
:param readonly: if :py:const:`True`, will begin a readonly
transaction, otherwise will begin as read-write
*New in version 2020.0.*
"""
return Transaction(self, autocommit=True, readonly=readonly,
# after, metadata, timeout
)
[docs] def begin(self, readonly=False,
# after=None, metadata=None, timeout=None
):
""" Begin a new :class:`~py2neo.Transaction`.
:param readonly: if :py:const:`True`, will begin a readonly
transaction, otherwise will begin as read-write
*Changed in version 2021.1: the 'autocommit' argument has been
removed. Use the 'auto' method instead.*
"""
return Transaction(self, autocommit=False, readonly=readonly,
# after, metadata, timeout
)
[docs] def commit(self, tx):
""" Commit a transaction.
*New in version 2021.1.*
"""
if tx is None:
return
if not isinstance(tx, Transaction):
raise TypeError("Bad transaction %r" % tx)
if tx.closed:
raise TypeError("Cannot commit closed transaction")
try:
summary = self.service.connector.commit(tx.ref)
tx._bookmark = summary["bookmark"]
tx._profile = summary["profile"]
tx._time = summary["time"]
finally:
tx._closed = True
[docs] def rollback(self, tx):
""" Rollback a transaction.
*New in version 2021.1.*
"""
if tx is None or tx.closed:
return
if not isinstance(tx, Transaction):
raise TypeError("Bad transaction %r" % tx)
try:
summary = self.service.connector.rollback(tx.ref)
tx._bookmark = summary["bookmark"]
tx._profile = summary["profile"]
tx._time = summary["time"]
except (ConnectionUnavailable, ConnectionBroken):
pass
finally:
tx._closed = True
# CYPHER EXECUTION #
[docs] def run(self, cypher, parameters=None, **kwparameters):
""" Run a single read/write query within an auto-commit
:class:`~py2neo.Transaction`.
:param cypher: Cypher statement
:param parameters: dictionary of parameters
:param kwparameters: extra parameters supplied as keyword
arguments
:return:
"""
return self.auto().run(cypher, parameters, **kwparameters)
[docs] def evaluate(self, cypher, parameters=None, **kwparameters):
""" Run a :meth:`~py2neo.Transaction.evaluate` operation within an
auto-commit :class:`~py2neo.Transaction`.
:param cypher: Cypher statement
:param parameters: dictionary of parameters
:return: first value from the first record returned or
:py:const:`None`.
"""
return self.run(cypher, parameters, **kwparameters).evaluate()
[docs] def update(self, cypher, parameters=None, timeout=None):
""" Call a function representing a transactional unit of work.
The function must always accept a :class:`~py2neo.Transaction`
object as its first argument. Additional arguments can be
passed though the `args` and `kwargs` arguments of this method.
The unit of work may be called multiple times if earlier
attempts fail due to connectivity or other transient errors.
As such, the function should have no non-idempotent side
effects.
:param cypher: cypher string or transaction function containing
a unit of work
:param parameters: cypher parameter map or function arguments
:param timeout:
:raises WriteServiceUnavailable: if the update does not
successfully complete
"""
if callable(cypher):
if parameters is None:
self._update(cypher, timeout=timeout)
elif (isinstance(parameters, tuple) and len(parameters) == 2 and
isinstance(parameters[0], Sequence) and isinstance(parameters[1], Mapping)):
self._update(lambda tx: cypher(tx, *parameters[0], **parameters[1]),
timeout=timeout)
elif isinstance(parameters, Sequence):
self._update(lambda tx: cypher(tx, *parameters), timeout=timeout)
elif isinstance(parameters, Mapping):
self._update(lambda tx: cypher(tx, **parameters), timeout=timeout)
else:
raise TypeError("Unrecognised parameter type")
else:
self._update(lambda tx: tx.update(cypher, parameters), timeout=timeout)
def _update(self, f, timeout=None):
from py2neo.timing import Timer
# TODO: logging
n = 0
for _ in Timer.repeat(at_least=3, timeout=timeout):
n += 1
tx = None
try:
tx = self.begin(
# after=after, metadata=metadata, timeout=timeout
)
value = f(tx)
if isgenerator(value):
_ = list(value) # exhaust the generator
self.commit(tx)
except (ConnectionUnavailable, ConnectionBroken, ConnectionLimit):
self.rollback(tx)
continue
except Neo4jError as error:
self.rollback(tx)
if error.should_invalidate_routing_table():
self.service.connector.invalidate_routing_table(self.name)
if error.should_retry():
continue
else:
raise
except Exception:
self.rollback(tx)
raise
else:
return
raise WriteServiceUnavailable("Failed to execute update after %r tries" % n)
[docs] def query(self, cypher, parameters=None, timeout=None):
""" Run a single readonly query within an auto-commit
:class:`~py2neo.Transaction`.
:param cypher: Cypher statement
:param parameters: dictionary of parameters
:param timeout:
:returns:
:raises TypeError: if the underlying connection profile does not
support readonly transactions
:raises ServiceUnavailable: if the query does not successfully
complete
*Refactored from read to query in version 2021.1*
"""
from py2neo.timing import Timer
# TODO: logging
n = 0
for _ in Timer.repeat(at_least=3, timeout=timeout):
n += 1
try:
result = self.auto(readonly=True).run(cypher, parameters)
except (ConnectionUnavailable, ConnectionBroken, ConnectionLimit):
continue
except Neo4jError as error:
if error.should_invalidate_routing_table():
self.service.connector.invalidate_routing_table(self.name)
if error.should_retry():
continue
else:
raise
else:
return result
raise ServiceUnavailable("Failed to execute query after %r tries" % n)
@property
def call(self):
""" Accessor for listing and calling procedures.
This property contains a :class:`.ProcedureLibrary` object tied
to this graph, which provides links to Cypher procedures in
the underlying implementation.
Calling a procedure requires only the regular Python function
call syntax::
>>> g = Graph()
>>> g.call.dbms.components()
name | versions | edition
--------------|------------|-----------
Neo4j Kernel | ['3.5.12'] | community
The object returned from the call is a
:class:`~py2neo.Cursor` object, identical to
that obtained from running a normal Cypher query, and can
therefore be consumed in a similar way.
Procedure names can alternatively be supplied as a string::
>>> g.call["dbms.components"]()
name | versions | edition
--------------|------------|-----------
Neo4j Kernel | ['3.5.12'] | community
Using :func:`dir` or :func:`iter` on the `call` attribute will
yield a list of available procedure names.
*New in version 2020.0.*
"""
return self._procedures
[docs] def delete_all(self):
""" Delete all nodes and relationships from this :class:`.Graph`.
.. warning::
This method will permanently remove **all** nodes and relationships
from the graph and cannot be undone.
"""
self.run("MATCH (a) DETACH DELETE a")
@deprecated("The graph.read(...) method is deprecated, "
"use graph.query(...) instead")
def read(self, cypher, parameters=None, **kwparameters):
return self.query(cypher, dict(parameters or {}, **kwparameters))
# SUBGRAPH OPERATIONS #
[docs] def create(self, subgraph):
""" Run a :meth:`~py2neo.Transaction.create` operation within a
:class:`~py2neo.Transaction`.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph`
"""
self.update(lambda tx: tx.create(subgraph))
[docs] def delete(self, subgraph):
""" Run a :meth:`~py2neo.Transaction.delete` operation within an
auto-commit :class:`~py2neo.Transaction`. To delete only the
relationships, use the :meth:`.separate` method.
Note that only entities which are bound to corresponding
remote entities though the ``graph`` and ``identity``
attributes will trigger a deletion.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph` object
"""
self.update(lambda tx: tx.delete(subgraph))
[docs] def exists(self, subgraph):
""" Run a :meth:`~py2neo.Transaction.exists` operation within an
auto-commit :class:`~py2neo.Transaction`.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph` object
:return:
"""
return self.auto(readonly=True).exists(subgraph)
[docs] def match(self, nodes=None, r_type=None, limit=None):
""" Match and return all relationships with specific criteria.
For example, to find all of Alice's friends::
for rel in graph.match((alice, ), r_type="FRIEND"):
print(rel.end_node["name"])
:param nodes: Sequence or Set of start and end nodes (:const:`None` means any node);
a Set implies a match in any direction
:param r_type: type of relationships to match (:const:`None` means any type)
:param limit: maximum number of relationships to match (:const:`None` means unlimited)
"""
return RelationshipMatcher(self).match(nodes=nodes, r_type=r_type).limit(limit)
[docs] def match_one(self, nodes=None, r_type=None):
""" Match and return one relationship with specific criteria.
:param nodes: Sequence or Set of start and end nodes (:const:`None` means any node);
a Set implies a match in any direction
:param r_type: type of relationships to match (:const:`None` means any type)
"""
matches = self.match(nodes=nodes, r_type=r_type, limit=1)
rels = list(matches)
if rels:
return rels[0]
else:
return None
[docs] def merge(self, subgraph, label=None, *property_keys):
""" Run a :meth:`~py2neo.Transaction.merge` operation within an
auto-commit :class:`~py2neo.Transaction`.
The example code below shows a simple merge for a new relationship
between two new nodes:
>>> from py2neo import Graph, Node, Relationship
>>> g = Graph()
>>> a = Node("Person", name="Alice", age=33)
>>> b = Node("Person", name="Bob", age=44)
>>> KNOWS = Relationship.type("KNOWS")
>>> g.merge(KNOWS(a, b), "Person", "name")
Following on, we then create a third node (of a different type) to
which both the original nodes connect:
>>> c = Node("Company", name="ACME")
>>> c.__primarylabel__ = "Company"
>>> c.__primarykey__ = "name"
>>> WORKS_FOR = Relationship.type("WORKS_FOR")
>>> g.merge(WORKS_FOR(a, c) | WORKS_FOR(b, c))
For details of how the merge algorithm works, see the
:meth:`~py2neo.Transaction.merge` method. Note that this is different
to a Cypher MERGE.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph` object
:param label: label on which to match any existing nodes
:param property_keys: property keys on which to match any existing nodes
"""
self.update(lambda tx: tx.merge(subgraph, label, *property_keys))
@property
def nodes(self):
""" A :class:`.NodeMatcher` for this graph.
This can be used to find nodes that match given criteria:
>>> graph = Graph()
>>> graph.nodes[1234]
(_1234:Person {name: 'Alice'})
>>> graph.nodes.get(1234)
(_1234:Person {name: 'Alice'})
>>> graph.nodes.match("Person", name="Alice").first()
(_1234:Person {name: 'Alice'})
Nodes can also be efficiently counted using this attribute:
>>> len(graph.nodes)
55691
>>> len(graph.nodes.match("Person", age=33))
12
"""
return NodeMatcher(self)
[docs] def pull(self, subgraph):
""" Pull data to one or more entities from their remote counterparts.
:param subgraph: the collection of nodes and relationships to pull
"""
self.update(lambda tx: tx.pull(subgraph))
[docs] def push(self, subgraph):
""" Push data from one or more entities to their remote counterparts.
:param subgraph: the collection of nodes and relationships to push
"""
self.update(lambda tx: tx.push(subgraph))
@property
def relationships(self):
""" A :class:`.RelationshipMatcher` for this graph.
This can be used to find relationships that match given criteria
as well as efficiently count relationships.
"""
return RelationshipMatcher(self)
[docs] def separate(self, subgraph):
""" Run a :meth:`~py2neo.Transaction.separate`
operation within an auto-commit :class:`~py2neo.Transaction`.
Note that only relationships which are bound to corresponding
remote relationships though the ``graph`` and ``identity``
attributes will trigger a deletion.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph`
"""
self.update(lambda tx: tx.separate(subgraph))
[docs]class SystemGraph(Graph):
""" A subclass of :class:`.Graph` that provides access to the
system database for the remote DBMS. This is only available in
Neo4j 4.0 and above.
*New in version 2020.0.*
"""
def __init__(self, profile=None, **settings):
settings["name"] = "system"
super(SystemGraph, self).__init__(profile, **settings)
def __repr__(self):
return "%s(%r)" % (self.__class__.__name__, self.service.uri)
[docs]class Schema(object):
""" The schema resource attached to a `Graph` instance.
"""
def __init__(self, graph):
self.graph = graph
@property
def node_labels(self):
""" The set of node labels currently defined within the graph.
"""
return frozenset(record[0] for record in
self.graph.run("CALL db.labels"))
@property
def relationship_types(self):
""" The set of relationship types currently defined within the graph.
"""
return frozenset(record[0] for record in
self.graph.run("CALL db.relationshipTypes"))
[docs] def create_index(self, label, *property_keys):
""" Create a schema index for a label and property
key combination.
"""
cypher = "CREATE INDEX ON :{}({})".format(
cypher_escape(label), ", ".join(map(cypher_escape, property_keys)))
self.graph.update(cypher)
while property_keys not in self.get_indexes(label):
sleep(0.1)
[docs] def create_uniqueness_constraint(self, label, property_key):
""" Create a node uniqueness constraint for a given label and property
key.
While indexes support the use of composite keys, unique constraints may
only be tied to a single property key.
"""
cypher = "CREATE CONSTRAINT ON (_:{}) ASSERT _.{} IS UNIQUE".format(
cypher_escape(label), cypher_escape(property_key))
self.graph.update(cypher)
while property_key not in self.get_uniqueness_constraints(label):
sleep(0.1)
[docs] def drop_index(self, label, *property_keys):
""" Remove label index for a given property key.
"""
cypher = "DROP INDEX ON :{}({})".format(
cypher_escape(label), ", ".join(map(cypher_escape, property_keys)))
self.graph.update(cypher)
[docs] def drop_uniqueness_constraint(self, label, property_key):
""" Remove the node uniqueness constraint for a given label and
property key.
"""
cypher = "DROP CONSTRAINT ON (_:{}) ASSERT _.{} IS UNIQUE".format(
cypher_escape(label), cypher_escape(property_key))
self.graph.update(cypher)
def _get_indexes(self, label, unique_only=False):
indexes = []
result = self.graph.run("CALL db.indexes")
for record in result:
properties = []
# The code branches here depending on the format of the response
# from the `db.indexes` procedure, which has varied enormously
# since 3.0.
if len(record) == 10:
if "labelsOrTypes" in result.keys():
# 4.0.0
# ['id', 'name', 'state', 'populationPercent',
# 'uniqueness', 'type', 'entityType', 'labelsOrTypes',
# 'properties', 'provider']
(id_, name, state, population_percent, uniqueness, type_,
entity_type, token_names, properties, provider) = record
description = None
# The 'type' field has randomly changed its meaning in 4.0,
# holding for example 'BTREE' instead of for example
# 'node_unique_property'. To check for uniqueness, we now
# need to look at the new 'uniqueness' field.
is_unique = uniqueness == "UNIQUE"
else:
# 3.5.3
# ['description', 'indexName', 'tokenNames', 'properties',
# 'state', 'type', 'progress', 'provider', 'id',
# 'failureMessage']
(description, index_name, token_names, properties, state,
type_, progress, provider, id_, failure_message) = record
is_unique = type_ == "node_unique_property"
elif len(record) == 7:
# 3.4.10
(description, lbl, properties, state,
type_, provider, failure_message) = record
is_unique = type_ == "node_unique_property"
token_names = [lbl]
elif len(record) == 6:
# 3.4.7
description, lbl, properties, state, type_, provider = record
is_unique = type_ == "node_unique_property"
token_names = [lbl]
elif len(record) == 3:
# 3.0.10
description, state, type_ = record
is_unique = type_ == "node_unique_property"
token_names = []
else:
raise RuntimeError("Unexpected response from procedure "
"db.indexes (%d fields)" % len(record))
if state not in (u"ONLINE", u"online"):
continue
if unique_only and not is_unique:
continue
if not token_names or not properties:
if description:
from py2neo.cypher.lexer import CypherLexer
from pygments.token import Token
tokens = list(CypherLexer().get_tokens(description))
for token_type, token_value in tokens:
if token_type is Token.Name.Label:
token_names.append(token_value.strip("`"))
elif token_type is Token.Name.Variable:
properties.append(token_value.strip("`"))
if not token_names or not properties:
continue
if label in token_names:
indexes.append(tuple(properties))
return indexes
[docs] def get_indexes(self, label):
""" Fetch a list of indexed property keys for a label.
"""
return self._get_indexes(label)
[docs] def get_uniqueness_constraints(self, label):
""" Fetch a list of unique constraints for a label. Each constraint is
the name of a single property key.
"""
return [k[0] for k in self._get_indexes(label, unique_only=True)]
[docs]class Transaction(object):
""" Logical context for one or more graph operations.
Transaction objects are typically constructed by the
:meth:`.Graph.auto` and :meth:`.Graph.begin` methods.
Likewise, the :meth:`.Graph.commit` and :meth:`.Graph.rollback`
methods can be used to finish a transaction.
"""
def __init__(self, graph, autocommit=False, readonly=False,
# after=None, metadata=None, timeout=None
):
self._graph = graph
self._autocommit = autocommit
self._connector = self.graph.service.connector
if autocommit:
self._ref = None
else:
self._ref = self._connector.begin(self.graph.name, readonly=readonly,
# after, metadata, timeout
)
self._readonly = readonly
self._closed = False
self._bookmark = None
self._profile = None
self._time = None
@property
def graph(self):
""" Graph to which this transaction belongs.
"""
return self._graph
@property
def ref(self):
""" Transaction reference.
"""
return self._ref
@property
def readonly(self):
""" :py:const:`True` if this is a readonly transaction,
:py:const:`False` otherwise.
"""
return self._readonly
@property
def closed(self):
""" :py:const:`True` if this transaction is closed,
:py:const:`False` otherwise.
"""
return self._closed
@property
def bookmark(self):
""" The closing bookmark for this transaction, populated
on commit.
"""
return self._bookmark
@property
def profile(self):
""" The connection profile under which this transaction was
carried out.
"""
return self._profile
@property
def time(self):
""" The total time taken to carry out this transaction
"""
return self._time
[docs] def run(self, cypher, parameters=None, **kwparameters):
""" Send a Cypher query to the server for execution and return
a :py:class:`~.cypher.Cursor` for navigating its result.
:param cypher: Cypher query
:param parameters: dictionary of parameters
:returns: :py:class:`~.cypher.Cursor` object
"""
from py2neo.client import Connection
if self.closed:
raise TypeError("Cannot run query in closed transaction")
try:
hydrant = Connection.default_hydrant(self._connector.profile, self.graph)
parameters = dict(parameters or {}, **kwparameters)
if self.ref:
result = self._connector.run(self.ref, cypher, parameters)
else:
result = self._connector.auto_run(cypher, parameters,
graph_name=self.graph.name,
readonly=self.readonly)
return Cursor(result, hydrant)
finally:
if not self.ref:
self._closed = True
[docs] def evaluate(self, cypher, parameters=None, **kwparameters):
""" Execute a single Cypher query and return the value from
the first column of the first record.
:param cypher: Cypher statement
:param parameters: dictionary of parameters
:returns: single return value or :const:`None`
"""
return self.run(cypher, parameters, **kwparameters).evaluate(0)
[docs] def update(self, cypher, parameters=None, **kwparameters):
""" Execute a single Cypher statement and discard any result
returned.
:param cypher: Cypher statement
:param parameters: dictionary of parameters
"""
self.run(cypher, parameters, **kwparameters)
@deprecated("The transaction.commit() method is deprecated, "
"use graph.commit(transaction) instead")
def commit(self):
""" Commit the transaction.
"""
return self.graph.commit(self)
@deprecated("The transaction.rollback() method is deprecated, "
"use graph.rollback(transaction) instead")
def rollback(self):
""" Roll back the current transaction, undoing all actions
previously taken.
"""
return self.graph.rollback(self)
[docs] def create(self, subgraph):
""" Create remote nodes and relationships that correspond to those in a
local subgraph. Any entities in *subgraph* that are already bound to
remote entities will remain unchanged, those which are not will become
bound to their newly-created counterparts.
For example::
>>> from py2neo import Graph, Node, Relationship
>>> g = Graph()
>>> tx = g.begin()
>>> a = Node("Person", name="Alice")
>>> tx.create(a)
>>> b = Node("Person", name="Bob")
>>> ab = Relationship(a, "KNOWS", b)
>>> tx.create(ab)
>>> tx.commit()
>>> g.exists(ab)
True
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
creatable object
"""
if self._autocommit:
raise TypeError("Create operations are not supported inside "
"auto-commit transactions")
try:
create = subgraph.__db_create__
except AttributeError:
raise TypeError("No method defined to create object %r" % subgraph)
else:
create(self)
[docs] def delete(self, subgraph):
""" Delete the remote nodes and relationships that correspond to
those in a local subgraph. To delete only the relationships, use
the :meth:`.separate` method.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph`
"""
try:
delete = subgraph.__db_delete__
except AttributeError:
raise TypeError("No method defined to delete object %r" % subgraph)
else:
delete(self)
[docs] def exists(self, subgraph):
""" Determine whether one or more entities all exist within the
graph. Note that if any nodes or relationships in *subgraph* are not
bound to remote counterparts, this method will return ``False``.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph`
:returns: ``True`` if all entities exist remotely, ``False`` otherwise
"""
try:
exists = subgraph.__db_exists__
except AttributeError:
raise TypeError("No method defined to check existence of object %r" % subgraph)
else:
return exists(self)
[docs] def merge(self, subgraph, primary_label=None, primary_key=None):
""" Create or update the nodes and relationships of a local
subgraph in the remote database. Note that the functionality of
this operation is not strictly identical to the Cypher MERGE
clause, although there is some overlap.
Each node and relationship in the local subgraph is merged
independently, with nodes merged first and relationships merged
second.
For each node, the merge is carried out by comparing that node with
a potential remote equivalent on the basis of a single label and
property value. If no remote match is found, a new node is created;
if a match is found, the labels and properties of the remote node
are updated. The label and property used for comparison are determined
by the `primary_label` and `primary_key` arguments but may be
overridden for individual nodes by the of `__primarylabel__` and
`__primarykey__` attributes on the node itself.
For each relationship, the merge is carried out by comparing that
relationship with a potential remote equivalent on the basis of matching
start and end nodes plus relationship type. If no remote match is found,
a new relationship is created; if a match is found, the properties of
the remote relationship are updated.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph` object
:param primary_label: label on which to match any existing nodes
:param primary_key: property key(s) on which to match any existing
nodes
"""
try:
merge = subgraph.__db_merge__
except AttributeError:
raise TypeError("No method defined to merge object %r" % subgraph)
else:
merge(self, primary_label, primary_key)
[docs] def pull(self, subgraph):
""" Update local entities from their remote counterparts.
For any nodes and relationships that exist in both the local
:class:`.Subgraph` and the remote :class:`.Graph`, pull properties
and node labels into the local copies. This operation does not
create or delete any entities.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph`
"""
try:
pull = subgraph.__db_pull__
except AttributeError:
raise TypeError("No method defined to pull object %r" % subgraph)
else:
return pull(self)
[docs] def push(self, subgraph):
""" Update remote entities from their local counterparts.
For any nodes and relationships that exist in both the local
:class:`.Subgraph` and the remote :class:`.Graph`, push properties
and node labels into the remote copies. This operation does not
create or delete any entities.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph`
"""
try:
push = subgraph.__db_push__
except AttributeError:
raise TypeError("No method defined to push object %r" % subgraph)
else:
return push(self)
[docs] def separate(self, subgraph):
""" Delete the remote relationships that correspond to those in a local
subgraph. This leaves any nodes untouched.
:param subgraph: a :class:`.Node`, :class:`.Relationship` or other
:class:`.Subgraph`
"""
try:
separate = subgraph.__db_separate__
except AttributeError:
raise TypeError("No method defined to separate object %r" % subgraph)
else:
separate(self)
