# Copyright 2013-2016 DataStax, Inc.
#
# 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.
import copy
from datetime import datetime, timedelta
from functools import partial
import time
import six
from warnings import warn
from cassandra.query import SimpleStatement
from cassandra.cqlengine import columns, CQLEngineException, ValidationError, UnicodeMixin
from cassandra.cqlengine import connection
from cassandra.cqlengine.functions import Token, BaseQueryFunction, QueryValue
from cassandra.cqlengine.operators import (InOperator, EqualsOperator, GreaterThanOperator,
GreaterThanOrEqualOperator, LessThanOperator,
LessThanOrEqualOperator, ContainsOperator, BaseWhereOperator)
from cassandra.cqlengine.statements import (WhereClause, SelectStatement, DeleteStatement,
UpdateStatement, InsertStatement,
BaseCQLStatement, MapDeleteClause, ConditionalClause)
class QueryException(CQLEngineException):
pass
class IfNotExistsWithCounterColumn(CQLEngineException):
pass
class IfExistsWithCounterColumn(CQLEngineException):
pass
[docs]class LWTException(CQLEngineException):
"""Lightweight conditional exception.
This exception will be raised when a write using an `IF` clause could not be
applied due to existing data violating the condition. The existing data is
available through the ``existing`` attribute.
:param existing: The current state of the data which prevented the write.
"""
def __init__(self, existing):
super(LWTException, self).__init__("LWT Query was not applied")
self.existing = existing
[docs]class DoesNotExist(QueryException):
pass
[docs]class MultipleObjectsReturned(QueryException):
pass
def check_applied(result):
"""
Raises LWTException if it looks like a failed LWT request.
"""
try:
applied = result.was_applied
except Exception:
applied = True # result was not LWT form
if not applied:
raise LWTException(result[0])
class AbstractQueryableColumn(UnicodeMixin):
"""
exposes cql query operators through pythons
builtin comparator symbols
"""
def _get_column(self):
raise NotImplementedError
def __unicode__(self):
raise NotImplementedError
def _to_database(self, val):
if isinstance(val, QueryValue):
return val
else:
return self._get_column().to_database(val)
def in_(self, item):
"""
Returns an in operator
used where you'd typically want to use python's `in` operator
"""
return WhereClause(six.text_type(self), InOperator(), item)
def contains_(self, item):
"""
Returns a CONTAINS operator
"""
return WhereClause(six.text_type(self), ContainsOperator(), item)
def __eq__(self, other):
return WhereClause(six.text_type(self), EqualsOperator(), self._to_database(other))
def __gt__(self, other):
return WhereClause(six.text_type(self), GreaterThanOperator(), self._to_database(other))
def __ge__(self, other):
return WhereClause(six.text_type(self), GreaterThanOrEqualOperator(), self._to_database(other))
def __lt__(self, other):
return WhereClause(six.text_type(self), LessThanOperator(), self._to_database(other))
def __le__(self, other):
return WhereClause(six.text_type(self), LessThanOrEqualOperator(), self._to_database(other))
class BatchType(object):
Unlogged = 'UNLOGGED'
Counter = 'COUNTER'
class BatchQuery(object):
"""
Handles the batching of queries
http://www.datastax.com/docs/1.2/cql_cli/cql/BATCH
"""
warn_multiple_exec = True
_consistency = None
def __init__(self, batch_type=None, timestamp=None, consistency=None, execute_on_exception=False,
timeout=connection.NOT_SET):
"""
:param batch_type: (optional) One of batch type values available through BatchType enum
:type batch_type: str or None
:param timestamp: (optional) A datetime or timedelta object with desired timestamp to be applied
to the batch conditional.
:type timestamp: datetime or timedelta or None
:param consistency: (optional) One of consistency values ("ANY", "ONE", "QUORUM" etc)
:type consistency: The :class:`.ConsistencyLevel` to be used for the batch query, or None.
:param execute_on_exception: (Defaults to False) Indicates that when the BatchQuery instance is used
as a context manager the queries accumulated within the context must be executed despite
encountering an error within the context. By default, any exception raised from within
the context scope will cause the batched queries not to be executed.
:type execute_on_exception: bool
:param timeout: (optional) Timeout for the entire batch (in seconds), if not specified fallback
to default session timeout
:type timeout: float or None
"""
self.queries = []
self.batch_type = batch_type
if timestamp is not None and not isinstance(timestamp, (datetime, timedelta)):
raise CQLEngineException('timestamp object must be an instance of datetime')
self.timestamp = timestamp
self._consistency = consistency
self._execute_on_exception = execute_on_exception
self._timeout = timeout
self._callbacks = []
self._executed = False
self._context_entered = False
def add_query(self, query):
if not isinstance(query, BaseCQLStatement):
raise CQLEngineException('only BaseCQLStatements can be added to a batch query')
self.queries.append(query)
def consistency(self, consistency):
self._consistency = consistency
def _execute_callbacks(self):
for callback, args, kwargs in self._callbacks:
callback(*args, **kwargs)
def add_callback(self, fn, *args, **kwargs):
"""Add a function and arguments to be passed to it to be executed after the batch executes.
A batch can support multiple callbacks.
Note, that if the batch does not execute, the callbacks are not executed.
A callback, thus, is an "on batch success" handler.
:param fn: Callable object
:type fn: callable
:param *args: Positional arguments to be passed to the callback at the time of execution
:param **kwargs: Named arguments to be passed to the callback at the time of execution
"""
if not callable(fn):
raise ValueError("Value for argument 'fn' is {0} and is not a callable object.".format(type(fn)))
self._callbacks.append((fn, args, kwargs))
def execute(self):
if self._executed and self.warn_multiple_exec:
msg = "Batch executed multiple times."
if self._context_entered:
msg += " If using the batch as a context manager, there is no need to call execute directly."
warn(msg)
self._executed = True
if len(self.queries) == 0:
# Empty batch is a no-op
# except for callbacks
self._execute_callbacks()
return
opener = 'BEGIN ' + (self.batch_type + ' ' if self.batch_type else '') + ' BATCH'
if self.timestamp:
if isinstance(self.timestamp, six.integer_types):
ts = self.timestamp
elif isinstance(self.timestamp, (datetime, timedelta)):
ts = self.timestamp
if isinstance(self.timestamp, timedelta):
ts += datetime.now() # Apply timedelta
ts = int(time.mktime(ts.timetuple()) * 1e+6 + ts.microsecond)
else:
raise ValueError("Batch expects a long, a timedelta, or a datetime")
opener += ' USING TIMESTAMP {0}'.format(ts)
query_list = [opener]
parameters = {}
ctx_counter = 0
for query in self.queries:
query.update_context_id(ctx_counter)
ctx = query.get_context()
ctx_counter += len(ctx)
query_list.append(' ' + str(query))
parameters.update(ctx)
query_list.append('APPLY BATCH;')
tmp = connection.execute('\n'.join(query_list), parameters, self._consistency, self._timeout)
check_applied(tmp)
self.queries = []
self._execute_callbacks()
def __enter__(self):
self._context_entered = True
return self
def __exit__(self, exc_type, exc_val, exc_tb):
# don't execute if there was an exception by default
if exc_type is not None and not self._execute_on_exception:
return
self.execute()
class AbstractQuerySet(object):
def __init__(self, model):
super(AbstractQuerySet, self).__init__()
self.model = model
# Where clause filters
self._where = []
# Conditional clause filters
self._conditional = []
# ordering arguments
self._order = []
self._allow_filtering = False
# CQL has a default limit of 10000, it's defined here
# because explicit is better than implicit
self._limit = 10000
# see the defer and only methods
self._defer_fields = set()
self._deferred_values = {}
self._only_fields = []
self._values_list = False
self._flat_values_list = False
# results cache
self._result_cache = None
self._result_idx = None
self._result_generator = None
self._materialize_results = True
self._distinct_fields = None
self._count = None
self._batch = None
self._ttl = getattr(model, '__default_ttl__', None)
self._consistency = None
self._timestamp = None
self._if_not_exists = False
self._timeout = connection.NOT_SET
self._if_exists = False
self._fetch_size = None
@property
def column_family_name(self):
return self.model.column_family_name()
def _execute(self, statement):
if self._batch:
return self._batch.add_query(statement)
else:
result = _execute_statement(self.model, statement, self._consistency, self._timeout)
if self._if_not_exists or self._if_exists or self._conditional:
check_applied(result)
return result
def __unicode__(self):
return six.text_type(self._select_query())
def __str__(self):
return str(self.__unicode__())
def __call__(self, *args, **kwargs):
return self.filter(*args, **kwargs)
def __deepcopy__(self, memo):
clone = self.__class__(self.model)
for k, v in self.__dict__.items():
if k in ['_con', '_cur', '_result_cache', '_result_idx', '_result_generator']: # don't clone these
clone.__dict__[k] = None
elif k == '_batch':
# we need to keep the same batch instance across
# all queryset clones, otherwise the batched queries
# fly off into other batch instances which are never
# executed, thx @dokai
clone.__dict__[k] = self._batch
elif k == '_timeout':
clone.__dict__[k] = self._timeout
else:
clone.__dict__[k] = copy.deepcopy(v, memo)
return clone
def __len__(self):
self._execute_query()
return self.count()
# ----query generation / execution----
def _select_fields(self):
""" returns the fields to select """
return []
def _validate_select_where(self):
""" put select query validation here """
def _select_query(self):
"""
Returns a select clause based on the given filter args
"""
if self._where:
self._validate_select_where()
return SelectStatement(
self.column_family_name,
fields=self._select_fields(),
where=self._where,
order_by=self._order,
limit=self._limit,
allow_filtering=self._allow_filtering,
distinct_fields=self._distinct_fields,
fetch_size=self._fetch_size
)
# ----Reads------
def _execute_query(self):
if self._batch:
raise CQLEngineException("Only inserts, updates, and deletes are available in batch mode")
if self._result_cache is None:
self._result_generator = (i for i in self._execute(self._select_query()))
self._result_cache = []
self._construct_result = self._maybe_inject_deferred(self._get_result_constructor())
# "DISTINCT COUNT()" is not supported in C* < 2.2, so we need to materialize all results to get
# len() and count() working with DISTINCT queries
if self._materialize_results or self._distinct_fields:
self._fill_result_cache()
def _fill_result_cache(self):
"""
Fill the result cache with all results.
"""
idx = 0
try:
while True:
idx += 1000
self._fill_result_cache_to_idx(idx)
except StopIteration:
pass
self._count = len(self._result_cache)
def _fill_result_cache_to_idx(self, idx):
self._execute_query()
if self._result_idx is None:
self._result_idx = -1
qty = idx - self._result_idx
if qty < 1:
return
else:
for idx in range(qty):
self._result_idx += 1
while True:
try:
self._result_cache[self._result_idx] = self._construct_result(self._result_cache[self._result_idx])
break
except IndexError:
self._result_cache.append(next(self._result_generator))
def __iter__(self):
self._execute_query()
idx = 0
while True:
if len(self._result_cache) <= idx:
try:
self._result_cache.append(next(self._result_generator))
except StopIteration:
break
instance = self._result_cache[idx]
if isinstance(instance, dict):
self._fill_result_cache_to_idx(idx)
yield self._result_cache[idx]
idx += 1
def __getitem__(self, s):
self._execute_query()
if isinstance(s, slice):
start = s.start if s.start else 0
# calculate the amount of results that need to be loaded
end = s.stop
if start < 0 or s.stop is None or s.stop < 0:
end = self.count()
try:
self._fill_result_cache_to_idx(end)
except StopIteration:
pass
return self._result_cache[start:s.stop:s.step]
else:
try:
s = int(s)
except (ValueError, TypeError):
raise TypeError('QuerySet indices must be integers')
# Using negative indexing is costly since we have to execute a count()
if s < 0:
num_results = self.count()
s += num_results
try:
self._fill_result_cache_to_idx(s)
except StopIteration:
raise IndexError
return self._result_cache[s]
def _get_result_constructor(self):
"""
Returns a function that will be used to instantiate query results
"""
raise NotImplementedError
@staticmethod
def _construct_with_deferred(f, deferred, row):
row.update(deferred)
return f(row)
def _maybe_inject_deferred(self, constructor):
return partial(self._construct_with_deferred, constructor, self._deferred_values)\
if self._deferred_values else constructor
def batch(self, batch_obj):
"""
Set a batch object to run the query on.
Note: running a select query with a batch object will raise an exception
"""
if batch_obj is not None and not isinstance(batch_obj, BatchQuery):
raise CQLEngineException('batch_obj must be a BatchQuery instance or None')
clone = copy.deepcopy(self)
clone._batch = batch_obj
return clone
def first(self):
try:
return six.next(iter(self))
except StopIteration:
return None
def all(self):
"""
Returns a queryset matching all rows
.. code-block:: python
for user in User.objects().all():
print(user)
"""
return copy.deepcopy(self)
def consistency(self, consistency):
"""
Sets the consistency level for the operation. See :class:`.ConsistencyLevel`.
.. code-block:: python
for user in User.objects(id=3).consistency(CL.ONE):
print(user)
"""
clone = copy.deepcopy(self)
clone._consistency = consistency
return clone
def _parse_filter_arg(self, arg):
"""
Parses a filter arg in the format:
<colname>__<op>
:returns: colname, op tuple
"""
statement = arg.rsplit('__', 1)
if len(statement) == 1:
return arg, None
elif len(statement) == 2:
return statement[0], statement[1]
else:
raise QueryException("Can't parse '{0}'".format(arg))
def iff(self, *args, **kwargs):
"""Adds IF statements to queryset"""
if len([x for x in kwargs.values() if x is None]):
raise CQLEngineException("None values on iff are not allowed")
clone = copy.deepcopy(self)
for operator in args:
if not isinstance(operator, ConditionalClause):
raise QueryException('{0} is not a valid query operator'.format(operator))
clone._conditional.append(operator)
for arg, val in kwargs.items():
if isinstance(val, Token):
raise QueryException("Token() values are not valid in conditionals")
col_name, col_op = self._parse_filter_arg(arg)
try:
column = self.model._get_column(col_name)
except KeyError:
raise QueryException("Can't resolve column name: '{0}'".format(col_name))
if isinstance(val, BaseQueryFunction):
query_val = val
else:
query_val = column.to_database(val)
operator_class = BaseWhereOperator.get_operator(col_op or 'EQ')
operator = operator_class()
clone._conditional.append(WhereClause(column.db_field_name, operator, query_val))
return clone
def filter(self, *args, **kwargs):
"""
Adds WHERE arguments to the queryset, returning a new queryset
See :ref:`retrieving-objects-with-filters`
Returns a QuerySet filtered on the keyword arguments
"""
# add arguments to the where clause filters
if len([x for x in kwargs.values() if x is None]):
raise CQLEngineException("None values on filter are not allowed")
clone = copy.deepcopy(self)
for operator in args:
if not isinstance(operator, WhereClause):
raise QueryException('{0} is not a valid query operator'.format(operator))
clone._where.append(operator)
for arg, val in kwargs.items():
col_name, col_op = self._parse_filter_arg(arg)
quote_field = True
if not isinstance(val, Token):
try:
column = self.model._get_column(col_name)
except KeyError:
raise QueryException("Can't resolve column name: '{0}'".format(col_name))
else:
if col_name != 'pk__token':
raise QueryException("Token() values may only be compared to the 'pk__token' virtual column")
column = columns._PartitionKeysToken(self.model)
quote_field = False
partition_columns = column.partition_columns
if len(partition_columns) != len(val.value):
raise QueryException(
'Token() received {0} arguments but model has {1} partition keys'.format(
len(val.value), len(partition_columns)))
val.set_columns(partition_columns)
# get query operator, or use equals if not supplied
operator_class = BaseWhereOperator.get_operator(col_op or 'EQ')
operator = operator_class()
if isinstance(operator, InOperator):
if not isinstance(val, (list, tuple)):
raise QueryException('IN queries must use a list/tuple value')
query_val = [column.to_database(v) for v in val]
elif isinstance(val, BaseQueryFunction):
query_val = val
elif (isinstance(operator, ContainsOperator) and
isinstance(column, (columns.List, columns.Set, columns.Map))):
# For ContainsOperator and collections, we query using the value, not the container
query_val = val
else:
query_val = column.to_database(val)
if not col_op: # only equal values should be deferred
clone._defer_fields.add(col_name)
clone._deferred_values[column.db_field_name] = val # map by db field name for substitution in results
clone._where.append(WhereClause(column.db_field_name, operator, query_val, quote_field=quote_field))
return clone
def get(self, *args, **kwargs):
"""
Returns a single instance matching this query, optionally with additional filter kwargs.
See :ref:`retrieving-objects-with-filters`
Returns a single object matching the QuerySet.
.. code-block:: python
user = User.get(id=1)
If no objects are matched, a :class:`~.DoesNotExist` exception is raised.
If more than one object is found, a :class:`~.MultipleObjectsReturned` exception is raised.
"""
if args or kwargs:
return self.filter(*args, **kwargs).get()
self._execute_query()
# Check that the resultset only contains one element, avoiding sending a COUNT query
try:
self[1]
raise self.model.MultipleObjectsReturned('Multiple objects found')
except IndexError:
pass
try:
obj = self[0]
except IndexError:
raise self.model.DoesNotExist
return obj
def _get_ordering_condition(self, colname):
order_type = 'DESC' if colname.startswith('-') else 'ASC'
colname = colname.replace('-', '')
return colname, order_type
def order_by(self, *colnames):
"""
Sets the column(s) to be used for ordering
Default order is ascending, prepend a '-' to any column name for descending
*Note: column names must be a clustering key*
.. code-block:: python
from uuid import uuid1,uuid4
class Comment(Model):
photo_id = UUID(primary_key=True)
comment_id = TimeUUID(primary_key=True, default=uuid1) # second primary key component is a clustering key
comment = Text()
sync_table(Comment)
u = uuid4()
for x in range(5):
Comment.create(photo_id=u, comment="test %d" % x)
print("Normal")
for comment in Comment.objects(photo_id=u):
print comment.comment_id
print("Reversed")
for comment in Comment.objects(photo_id=u).order_by("-comment_id"):
print comment.comment_id
"""
if len(colnames) == 0:
clone = copy.deepcopy(self)
clone._order = []
return clone
conditions = []
for colname in colnames:
conditions.append('"{0}" {1}'.format(*self._get_ordering_condition(colname)))
clone = copy.deepcopy(self)
clone._order.extend(conditions)
return clone
def count(self):
"""
Returns the number of rows matched by this query.
*Note: This function executes a SELECT COUNT() and has a performance cost on large datasets*
"""
if self._batch:
raise CQLEngineException("Only inserts, updates, and deletes are available in batch mode")
if self._count is None:
query = self._select_query()
query.count = True
result = self._execute(query)
count_row = result[0].popitem()
self._count = count_row[1]
return self._count
def distinct(self, distinct_fields=None):
"""
Returns the DISTINCT rows matched by this query.
distinct_fields default to the partition key fields if not specified.
*Note: distinct_fields must be a partition key or a static column*
.. code-block:: python
class Automobile(Model):
manufacturer = columns.Text(partition_key=True)
year = columns.Integer(primary_key=True)
model = columns.Text(primary_key=True)
price = columns.Decimal()
sync_table(Automobile)
# create rows
Automobile.objects.distinct()
# or
Automobile.objects.distinct(['manufacturer'])
"""
clone = copy.deepcopy(self)
if distinct_fields:
clone._distinct_fields = distinct_fields
else:
clone._distinct_fields = [x.column_name for x in self.model._partition_keys.values()]
return clone
def limit(self, v):
"""
Limits the number of results returned by Cassandra. Use *0* or *None* to disable.
*Note that CQL's default limit is 10,000, so all queries without a limit set explicitly will have an implicit limit of 10,000*
.. code-block:: python
# Fetch 100 users
for user in User.objects().limit(100):
print(user)
# Fetch all users
for user in User.objects().limit(None):
print(user)
"""
if v is None:
v = 0
if not isinstance(v, six.integer_types):
raise TypeError
if v == self._limit:
return self
if v < 0:
raise QueryException("Negative limit is not allowed")
clone = copy.deepcopy(self)
clone._limit = v
return clone
def fetch_size(self, v):
"""
Sets the number of rows that are fetched at a time.
*Note that driver's default fetch size is 5000.*
.. code-block:: python
for user in User.objects().fetch_size(500):
print(user)
"""
if not isinstance(v, six.integer_types):
raise TypeError
if v == self._fetch_size:
return self
if v < 1:
raise QueryException("fetch size less than 1 is not allowed")
clone = copy.deepcopy(self)
clone._fetch_size = v
return clone
def allow_filtering(self):
"""
Enables the (usually) unwise practive of querying on a clustering key without also defining a partition key
"""
clone = copy.deepcopy(self)
clone._allow_filtering = True
return clone
def _only_or_defer(self, action, fields):
if action == 'only' and self._only_fields:
raise QueryException("QuerySet already has 'only' fields defined")
clone = copy.deepcopy(self)
# check for strange fields
missing_fields = [f for f in fields if f not in self.model._columns.keys()]
if missing_fields:
raise QueryException(
"Can't resolve fields {0} in {1}".format(
', '.join(missing_fields), self.model.__name__))
if action == 'defer':
clone._defer_fields.update(fields)
elif action == 'only':
clone._only_fields = fields
else:
raise ValueError
return clone
def only(self, fields):
""" Load only these fields for the returned query """
return self._only_or_defer('only', fields)
def defer(self, fields):
""" Don't load these fields for the returned query """
return self._only_or_defer('defer', fields)
def create(self, **kwargs):
return self.model(**kwargs) \
.batch(self._batch) \
.ttl(self._ttl) \
.consistency(self._consistency) \
.if_not_exists(self._if_not_exists) \
.timestamp(self._timestamp) \
.if_exists(self._if_exists) \
.save()
def delete(self):
"""
Deletes the contents of a query
"""
# validate where clause
partition_keys = set(x.db_field_name for x in self.model._partition_keys.values())
if partition_keys - set(c.field for c in self._where):
raise QueryException("The partition key must be defined on delete queries")
dq = DeleteStatement(
self.column_family_name,
where=self._where,
timestamp=self._timestamp,
conditionals=self._conditional,
if_exists=self._if_exists
)
self._execute(dq)
def __eq__(self, q):
if len(self._where) == len(q._where):
return all([w in q._where for w in self._where])
return False
def __ne__(self, q):
return not (self != q)
def timeout(self, timeout):
"""
:param timeout: Timeout for the query (in seconds)
:type timeout: float or None
"""
clone = copy.deepcopy(self)
clone._timeout = timeout
return clone
class ResultObject(dict):
"""
adds attribute access to a dictionary
"""
def __getattr__(self, item):
try:
return self[item]
except KeyError:
raise AttributeError
class SimpleQuerySet(AbstractQuerySet):
"""
Overrides _get_result_constructor for querysets that do not define a model (e.g. NamedTable queries)
"""
def _get_result_constructor(self):
"""
Returns a function that will be used to instantiate query results
"""
return ResultObject
[docs]class ModelQuerySet(AbstractQuerySet):
"""
"""
def _validate_select_where(self):
""" Checks that a filterset will not create invalid select statement """
# check that there's either a =, a IN or a CONTAINS (collection) relationship with a primary key or indexed field
equal_ops = [self.model._get_column_by_db_name(w.field) for w in self._where if isinstance(w.operator, EqualsOperator)]
token_comparison = any([w for w in self._where if isinstance(w.value, Token)])
if not any(w.primary_key or w.index for w in equal_ops) and not token_comparison and not self._allow_filtering:
raise QueryException(('Where clauses require either =, a IN or a CONTAINS (collection) '
'comparison with either a primary key or indexed field'))
if not self._allow_filtering:
# if the query is not on an indexed field
if not any(w.index for w in equal_ops):
if not any([w.partition_key for w in equal_ops]) and not token_comparison:
raise QueryException('Filtering on a clustering key without a partition key is not allowed unless allow_filtering() is called on the querset')
def _select_fields(self):
if self._defer_fields or self._only_fields:
fields = self.model._columns.keys()
if self._defer_fields:
fields = [f for f in fields if f not in self._defer_fields]
elif self._only_fields:
fields = self._only_fields
return [self.model._columns[f].db_field_name for f in fields]
return super(ModelQuerySet, self)._select_fields()
def _get_result_constructor(self):
""" Returns a function that will be used to instantiate query results """
if not self._values_list: # we want models
return self.model._construct_instance
elif self._flat_values_list: # the user has requested flattened list (1 value per row)
key = self._only_fields[0]
return lambda row: row[key]
else:
return lambda row: [row[f] for f in self._only_fields]
def _get_ordering_condition(self, colname):
colname, order_type = super(ModelQuerySet, self)._get_ordering_condition(colname)
column = self.model._columns.get(colname)
if column is None:
raise QueryException("Can't resolve the column name: '{0}'".format(colname))
# validate the column selection
if not column.primary_key:
raise QueryException(
"Can't order on '{0}', can only order on (clustered) primary keys".format(colname))
pks = [v for k, v in self.model._columns.items() if v.primary_key]
if column == pks[0]:
raise QueryException(
"Can't order by the first primary key (partition key), clustering (secondary) keys only")
return column.db_field_name, order_type
def values_list(self, *fields, **kwargs):
""" Instructs the query set to return tuples, not model instance """
flat = kwargs.pop('flat', False)
if kwargs:
raise TypeError('Unexpected keyword arguments to values_list: %s'
% (kwargs.keys(),))
if flat and len(fields) > 1:
raise TypeError("'flat' is not valid when values_list is called with more than one field.")
clone = self.only(fields)
clone._values_list = True
clone._flat_values_list = flat
return clone
[docs] def ttl(self, ttl):
"""
Sets the ttl (in seconds) for modified data.
*Note that running a select query with a ttl value will raise an exception*
"""
clone = copy.deepcopy(self)
clone._ttl = ttl
return clone
[docs] def timestamp(self, timestamp):
"""
Allows for custom timestamps to be saved with the record.
"""
clone = copy.deepcopy(self)
clone._timestamp = timestamp
return clone
[docs] def if_not_exists(self):
"""
Check the existence of an object before insertion.
If the insertion isn't applied, a LWTException is raised.
"""
if self.model._has_counter:
raise IfNotExistsWithCounterColumn('if_not_exists cannot be used with tables containing counter columns')
clone = copy.deepcopy(self)
clone._if_not_exists = True
return clone
[docs] def if_exists(self):
"""
Check the existence of an object before an update or delete.
If the update or delete isn't applied, a LWTException is raised.
"""
if self.model._has_counter:
raise IfExistsWithCounterColumn('if_exists cannot be used with tables containing counter columns')
clone = copy.deepcopy(self)
clone._if_exists = True
return clone
[docs] def update(self, **values):
"""
Performs an update on the row selected by the queryset. Include values to update in the
update like so:
.. code-block:: python
Model.objects(key=n).update(value='x')
Passing in updates for columns which are not part of the model will raise a ValidationError.
Per column validation will be performed, but instance level validation will not
(i.e., `Model.validate` is not called). This is sometimes referred to as a blind update.
For example:
.. code-block:: python
class User(Model):
id = Integer(primary_key=True)
name = Text()
setup(["localhost"], "test")
sync_table(User)
u = User.create(id=1, name="jon")
User.objects(id=1).update(name="Steve")
# sets name to null
User.objects(id=1).update(name=None)
Also supported is blindly adding and removing elements from container columns,
without loading a model instance from Cassandra.
Using the syntax `.update(column_name={x, y, z})` will overwrite the contents of the container, like updating a
non container column. However, adding `__<operation>` to the end of the keyword arg, makes the update call add
or remove items from the collection, without overwriting then entire column.
Given the model below, here are the operations that can be performed on the different container columns:
.. code-block:: python
class Row(Model):
row_id = columns.Integer(primary_key=True)
set_column = columns.Set(Integer)
list_column = columns.List(Integer)
map_column = columns.Map(Integer, Integer)
:class:`~cqlengine.columns.Set`
- `add`: adds the elements of the given set to the column
- `remove`: removes the elements of the given set to the column
.. code-block:: python
# add elements to a set
Row.objects(row_id=5).update(set_column__add={6})
# remove elements to a set
Row.objects(row_id=5).update(set_column__remove={4})
:class:`~cqlengine.columns.List`
- `append`: appends the elements of the given list to the end of the column
- `prepend`: prepends the elements of the given list to the beginning of the column
.. code-block:: python
# append items to a list
Row.objects(row_id=5).update(list_column__append=[6, 7])
# prepend items to a list
Row.objects(row_id=5).update(list_column__prepend=[1, 2])
:class:`~cqlengine.columns.Map`
- `update`: adds the given keys/values to the columns, creating new entries if they didn't exist, and overwriting old ones if they did
.. code-block:: python
# add items to a map
Row.objects(row_id=5).update(map_column__update={1: 2, 3: 4})
"""
if not values:
return
nulled_columns = set()
us = UpdateStatement(self.column_family_name, where=self._where, ttl=self._ttl,
timestamp=self._timestamp, conditionals=self._conditional, if_exists=self._if_exists)
for name, val in values.items():
col_name, col_op = self._parse_filter_arg(name)
col = self.model._columns.get(col_name)
# check for nonexistant columns
if col is None:
raise ValidationError("{0}.{1} has no column named: {2}".format(self.__module__, self.model.__name__, col_name))
# check for primary key update attempts
if col.is_primary_key:
raise ValidationError("Cannot apply update to primary key '{0}' for {1}.{2}".format(col_name, self.__module__, self.model.__name__))
# we should not provide default values in this use case.
val = col.validate(val)
if val is None:
nulled_columns.add(col_name)
continue
us.add_update(col, val, operation=col_op)
if us.assignments:
self._execute(us)
if nulled_columns:
ds = DeleteStatement(self.column_family_name, fields=nulled_columns,
where=self._where, conditionals=self._conditional, if_exists=self._if_exists)
self._execute(ds)
class DMLQuery(object):
"""
A query object used for queries performing inserts, updates, or deletes
this is usually instantiated by the model instance to be modified
unlike the read query object, this is mutable
"""
_ttl = None
_consistency = None
_timestamp = None
_if_not_exists = False
_if_exists = False
def __init__(self, model, instance=None, batch=None, ttl=None, consistency=None, timestamp=None,
if_not_exists=False, conditional=None, timeout=connection.NOT_SET, if_exists=False):
self.model = model
self.column_family_name = self.model.column_family_name()
self.instance = instance
self._batch = batch
self._ttl = ttl
self._consistency = consistency
self._timestamp = timestamp
self._if_not_exists = if_not_exists
self._if_exists = if_exists
self._conditional = conditional
self._timeout = timeout
def _execute(self, statement):
if self._batch:
return self._batch.add_query(statement)
else:
results = _execute_statement(self.model, statement, self._consistency, self._timeout)
if self._if_not_exists or self._if_exists or self._conditional:
check_applied(results)
return results
def batch(self, batch_obj):
if batch_obj is not None and not isinstance(batch_obj, BatchQuery):
raise CQLEngineException('batch_obj must be a BatchQuery instance or None')
self._batch = batch_obj
return self
def _delete_null_columns(self):
"""
executes a delete query to remove columns that have changed to null
"""
ds = DeleteStatement(self.column_family_name, conditionals=self._conditional, if_exists=self._if_exists)
deleted_fields = False
for _, v in self.instance._values.items():
col = v.column
if v.deleted:
ds.add_field(col.db_field_name)
deleted_fields = True
elif isinstance(col, columns.Map):
uc = MapDeleteClause(col.db_field_name, v.value, v.previous_value)
if uc.get_context_size() > 0:
ds.add_field(uc)
deleted_fields = True
if deleted_fields:
for name, col in self.model._primary_keys.items():
ds.add_where(col, EqualsOperator(), getattr(self.instance, name))
self._execute(ds)
def update(self):
"""
updates a row.
This is a blind update call.
All validation and cleaning needs to happen
prior to calling this.
"""
if self.instance is None:
raise CQLEngineException("DML Query intance attribute is None")
assert type(self.instance) == self.model
null_clustering_key = False if len(self.instance._clustering_keys) == 0 else True
static_changed_only = True
statement = UpdateStatement(self.column_family_name, ttl=self._ttl, timestamp=self._timestamp,
conditionals=self._conditional, if_exists=self._if_exists)
for name, col in self.instance._clustering_keys.items():
null_clustering_key = null_clustering_key and col._val_is_null(getattr(self.instance, name, None))
# get defined fields and their column names
for name, col in self.model._columns.items():
# if clustering key is null, don't include non static columns
if null_clustering_key and not col.static and not col.partition_key:
continue
if not col.is_primary_key:
val = getattr(self.instance, name, None)
val_mgr = self.instance._values[name]
if val is None:
continue
if not val_mgr.changed and not isinstance(col, columns.Counter):
continue
static_changed_only = static_changed_only and col.static
statement.add_update(col, val, previous=val_mgr.previous_value)
if statement.assignments:
for name, col in self.model._primary_keys.items():
# only include clustering key if clustering key is not null, and non static columns are changed to avoid cql error
if (null_clustering_key or static_changed_only) and (not col.partition_key):
continue
statement.add_where(col, EqualsOperator(), getattr(self.instance, name))
self._execute(statement)
if not null_clustering_key:
self._delete_null_columns()
def save(self):
"""
Creates / updates a row.
This is a blind insert call.
All validation and cleaning needs to happen
prior to calling this.
"""
if self.instance is None:
raise CQLEngineException("DML Query intance attribute is None")
assert type(self.instance) == self.model
nulled_fields = set()
if self.instance._has_counter or self.instance._can_update():
if self.instance._has_counter:
warn("'create' and 'save' actions on Counters are deprecated. A future version will disallow this. Use the 'update' mechanism instead.")
return self.update()
else:
insert = InsertStatement(self.column_family_name, ttl=self._ttl, timestamp=self._timestamp, if_not_exists=self._if_not_exists)
static_save_only = False if len(self.instance._clustering_keys) == 0 else True
for name, col in self.instance._clustering_keys.items():
static_save_only = static_save_only and col._val_is_null(getattr(self.instance, name, None))
for name, col in self.instance._columns.items():
if static_save_only and not col.static and not col.partition_key:
continue
val = getattr(self.instance, name, None)
if col._val_is_null(val):
if self.instance._values[name].changed:
nulled_fields.add(col.db_field_name)
continue
insert.add_assignment(col, getattr(self.instance, name, None))
# skip query execution if it's empty
# caused by pointless update queries
if not insert.is_empty:
self._execute(insert)
# delete any nulled columns
if not static_save_only:
self._delete_null_columns()
def delete(self):
""" Deletes one instance """
if self.instance is None:
raise CQLEngineException("DML Query instance attribute is None")
ds = DeleteStatement(self.column_family_name, timestamp=self._timestamp, conditionals=self._conditional, if_exists=self._if_exists)
for name, col in self.model._primary_keys.items():
val = getattr(self.instance, name)
if val is None and not col.parition_key:
continue
ds.add_where(col, EqualsOperator(), val)
self._execute(ds)
def _execute_statement(model, statement, consistency_level, timeout):
params = statement.get_context()
s = SimpleStatement(str(statement), consistency_level=consistency_level, fetch_size=statement.fetch_size)
if model._partition_key_index:
key_values = statement.partition_key_values(model._partition_key_index)
if not any(v is None for v in key_values):
parts = model._routing_key_from_values(key_values, connection.get_cluster().protocol_version)
s.routing_key = parts
s.keyspace = model._get_keyspace()
return connection.execute(s, params, timeout=timeout)