# 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.

"""

This module holds classes for working with prepared statements and

specifying consistency levels and retry policies for individual

queries.

"""

from collections import namedtuple

from datetime import datetime, timedelta

import re

import struct

import time

import six

from six.moves import range, zip

from cassandra import ConsistencyLevel, OperationTimedOut

from cassandra.util import unix_time_from_uuid1

from cassandra.encoder import Encoder

import cassandra.encoder

from cassandra.protocol import _UNSET_VALUE

from cassandra.util import OrderedDict, _sanitize_identifiers

import logging

log = logging.getLogger(__name__)

UNSET_VALUE = _UNSET_VALUE

"""

Specifies an unset value when binding a prepared statement.

Unset values are ignored, allowing prepared statements to be used without specify

See https://issues.apache.org/jira/browse/CASSANDRA-7304 for further details on semantics.

.. versionadded:: 2.6.0

Only valid when using native protocol v4+

"""

NON_ALPHA_REGEX = re.compile('[^a-zA-Z0-9]')

START_BADCHAR_REGEX = re.compile('^[^a-zA-Z0-9]*')

END_BADCHAR_REGEX = re.compile('[^a-zA-Z0-9_]*$')

_clean_name_cache = {}

def _clean_column_name(name):

try:

return _clean_name_cache[name]

except KeyError:

clean = NON_ALPHA_REGEX.sub("_", START_BADCHAR_REGEX.sub("", END_BADCHAR_REGEX.sub("", name)))

_clean_name_cache[name] = clean

return clean

def tuple_factory(colnames, rows):

"""

Returns each row as a tuple

Example::

>>> from cassandra.query import tuple_factory

>>> session = cluster.connect('mykeyspace')

>>> session.row_factory = tuple_factory

>>> rows = session.execute("SELECT name, age FROM users LIMIT 1")

>>> print rows[0]

('Bob', 42)

.. versionchanged:: 2.0.0

moved from ``cassandra.decoder`` to ``cassandra.query``

"""

return rows

def named_tuple_factory(colnames, rows):

"""

Returns each row as a `namedtuple <https://docs.python.org/2/library/collections.html#collections.namedtuple>`_.

This is the default row factory.

Example::

>>> from cassandra.query import named_tuple_factory

>>> session = cluster.connect('mykeyspace')

>>> session.row_factory = named_tuple_factory

>>> rows = session.execute("SELECT name, age FROM users LIMIT 1")

>>> user = rows[0]

>>> # you can access field by their name:

>>> print "name: %s, age: %d" % (user.name, user.age)

name: Bob, age: 42

>>> # or you can access fields by their position (like a tuple)

>>> name, age = user

>>> print "name: %s, age: %d" % (name, age)

name: Bob, age: 42

>>> name = user[0]

>>> age = user[1]

>>> print "name: %s, age: %d" % (name, age)

name: Bob, age: 42

.. versionchanged:: 2.0.0

moved from ``cassandra.decoder`` to ``cassandra.query``

"""

clean_column_names = map(_clean_column_name, colnames)

try:

Row = namedtuple('Row', clean_column_names)

except Exception:

clean_column_names = list(map(_clean_column_name, colnames)) # create list because py3 map object will be consumed by first attempt

log.warning("Failed creating named tuple for results with column names %s (cleaned: %s) "

"(see Python 'namedtuple' documentation for details on name rules). "

"Results will be returned with positional names. "

"Avoid this by choosing different names, using SELECT \"<col name>\" AS aliases, "

"or specifying a different row_factory on your Session" %

(colnames, clean_column_names))

Row = namedtuple('Row', _sanitize_identifiers(clean_column_names))

return [Row(*row) for row in rows]

def dict_factory(colnames, rows):

"""

Returns each row as a dict.

Example::

>>> from cassandra.query import dict_factory

>>> session = cluster.connect('mykeyspace')

>>> session.row_factory = dict_factory

>>> rows = session.execute("SELECT name, age FROM users LIMIT 1")

>>> print rows[0]

{u'age': 42, u'name': u'Bob'}

.. versionchanged:: 2.0.0

moved from ``cassandra.decoder`` to ``cassandra.query``

"""

return [dict(zip(colnames, row)) for row in rows]

def ordered_dict_factory(colnames, rows):

"""

Like :meth:`~cassandra.query.dict_factory`, but returns each row as an OrderedDict,

so the order of the columns is preserved.

.. versionchanged:: 2.0.0

moved from ``cassandra.decoder`` to ``cassandra.query``

"""

return [OrderedDict(zip(colnames, row)) for row in rows]

FETCH_SIZE_UNSET = object()

class Statement(object):

"""

An abstract class representing a single query. There are three subclasses:

:class:`.SimpleStatement`, :class:`.BoundStatement`, and :class:`.BatchStatement`.

These can be passed to :meth:`.Session.execute()`.

"""

retry_policy = None

"""

An instance of a :class:`cassandra.policies.RetryPolicy` or one of its

subclasses. This controls when a query will be retried and how it

will be retried.

"""

consistency_level = None

"""

The :class:`.ConsistencyLevel` to be used for this operation. Defaults

to :const:`None`, which means that the default consistency level for

the Session this is executed in will be used.

"""

fetch_size = FETCH_SIZE_UNSET

"""

How many rows will be fetched at a time. This overrides the default

of :attr:`.Session.default_fetch_size`

.. versionadded:: 2.0.0

"""

keyspace = None

"""

The string name of the keyspace this query acts on. This is used when

:class:`~.TokenAwarePolicy` is configured for

:attr:`.Cluster.load_balancing_policy`

It is set implicitly on :class:`.BoundStatement`, and :class:`.BatchStatement`,

but must be set explicitly on :class:`.SimpleStatement`.

.. versionadded:: 2.1.3

"""

custom_payload = None

"""

:ref:`custom_payload` to be passed to the server.

These are only allowed when using protocol version 4 or higher.

.. versionadded:: 2.6.0

"""

is_idempotent = False

"""

Flag indicating whether this statement is safe to run multiple times in speculative execution.

"""

_serial_consistency_level = None

_routing_key = None

def __init__(self, retry_policy=None, consistency_level=None, routing_key=None,

serial_consistency_level=None, fetch_size=FETCH_SIZE_UNSET, keyspace=None, custom_payload=None,

is_idempotent=False):

if retry_policy and not hasattr(retry_policy, 'on_read_timeout'): # just checking one method to detect positional parameter errors

raise ValueError('retry_policy should implement cassandra.policies.RetryPolicy')

self.retry_policy = retry_policy

if consistency_level is not None:

self.consistency_level = consistency_level

self._routing_key = routing_key

if serial_consistency_level is not None:

self.serial_consistency_level = serial_consistency_level

if fetch_size is not FETCH_SIZE_UNSET:

self.fetch_size = fetch_size

if keyspace is not None:

self.keyspace = keyspace

if custom_payload is not None:

self.custom_payload = custom_payload

self.is_idempotent = is_idempotent

def _key_parts_packed(self, parts):

for p in parts:

l = len(p)

yield struct.pack(">H%dsB" % l, l, p, 0)

def _get_routing_key(self):

return self._routing_key

def _set_routing_key(self, key):

if isinstance(key, (list, tuple)):

if len(key) == 1:

self._routing_key = key[0]

else:

self._routing_key = b"".join(self._key_parts_packed(key))

else:

self._routing_key = key

def _del_routing_key(self):

self._routing_key = None

routing_key = property(

_get_routing_key,

_set_routing_key,

_del_routing_key,

"""

The :attr:`~.TableMetadata.partition_key` portion of the primary key,

which can be used to determine which nodes are replicas for the query.

If the partition key is a composite, a list or tuple must be passed in.

Each key component should be in its packed (binary) format, so all

components should be strings.

""")

def _get_serial_consistency_level(self):

return self._serial_consistency_level

def _set_serial_consistency_level(self, serial_consistency_level):

acceptable = (None, ConsistencyLevel.SERIAL, ConsistencyLevel.LOCAL_SERIAL)

if serial_consistency_level not in acceptable:

raise ValueError(

"serial_consistency_level must be either ConsistencyLevel.SERIAL "

"or ConsistencyLevel.LOCAL_SERIAL")

self._serial_consistency_level = serial_consistency_level

def _del_serial_consistency_level(self):

self._serial_consistency_level = None

serial_consistency_level = property(

_get_serial_consistency_level,

_set_serial_consistency_level,

_del_serial_consistency_level,

"""

The serial consistency level is only used by conditional updates

(``INSERT``, ``UPDATE`` and ``DELETE`` with an ``IF`` condition). For

those, the ``serial_consistency_level`` defines the consistency level of

the serial phase (or "paxos" phase) while the normal

:attr:`~.consistency_level` defines the consistency for the "learn" phase,

i.e. what type of reads will be guaranteed to see the update right away.

For example, if a conditional write has a :attr:`~.consistency_level` of

:attr:`~.ConsistencyLevel.QUORUM` (and is successful), then a

:attr:`~.ConsistencyLevel.QUORUM` read is guaranteed to see that write.

But if the regular :attr:`~.consistency_level` of that write is

:attr:`~.ConsistencyLevel.ANY`, then only a read with a

:attr:`~.consistency_level` of :attr:`~.ConsistencyLevel.SERIAL` is

guaranteed to see it (even a read with consistency

:attr:`~.ConsistencyLevel.ALL` is not guaranteed to be enough).

The serial consistency can only be one of :attr:`~.ConsistencyLevel.SERIAL`

or :attr:`~.ConsistencyLevel.LOCAL_SERIAL`. While ``SERIAL`` guarantees full

linearizability (with other ``SERIAL`` updates), ``LOCAL_SERIAL`` only

guarantees it in the local data center.

The serial consistency level is ignored for any query that is not a

conditional update. Serial reads should use the regular

:attr:`consistency_level`.

See :doc:`/lwt` for a discussion on how to work with results returned from

conditional statements.

.. versionadded:: 2.0.0

""")

class SimpleStatement(Statement):

"""

A simple, un-prepared query.

"""

def __init__(self, query_string, retry_policy=None, consistency_level=None, routing_key=None,

serial_consistency_level=None, fetch_size=FETCH_SIZE_UNSET, keyspace=None,

custom_payload=None, is_idempotent=False):

"""

`query_string` should be a literal CQL statement with the exception

of parameter placeholders that will be filled through the

`parameters` argument of :meth:`.Session.execute()`.

See :class:`Statement` attributes for a description of the other parameters.

"""

Statement.__init__(self, retry_policy, consistency_level, routing_key,

serial_consistency_level, fetch_size, keyspace, custom_payload, is_idempotent)

self._query_string = query_string

@property

def query_string(self):

return self._query_string

def __str__(self):

consistency = ConsistencyLevel.value_to_name.get(self.consistency_level, 'Not Set')

return (u'<SimpleStatement query="%s", consistency=%s>' %

(self.query_string, consistency))

__repr__ = __str__

class PreparedStatement(object):

"""

A statement that has been prepared against at least one Cassandra node.

Instances of this class should not be created directly, but through

:meth:`.Session.prepare()`.

A :class:`.PreparedStatement` should be prepared only once. Re-preparing a statement

may affect performance (as the operation requires a network roundtrip).

"""

column_metadata = None #TODO: make this bind_metadata in next major

consistency_level = None

custom_payload = None

fetch_size = FETCH_SIZE_UNSET

keyspace = None # change to prepared_keyspace in major release

protocol_version = None

query_id = None

query_string = None

result_metadata = None

routing_key_indexes = None

_routing_key_index_set = None

serial_consistency_level = None

def __init__(self, column_metadata, query_id, routing_key_indexes, query,

keyspace, protocol_version, result_metadata):

self.column_metadata = column_metadata

self.query_id = query_id

self.routing_key_indexes = routing_key_indexes

self.query_string = query

self.keyspace = keyspace

self.protocol_version = protocol_version

self.result_metadata = result_metadata

self.is_idempotent = False

@classmethod

def from_message(cls, query_id, column_metadata, pk_indexes, cluster_metadata,

query, prepared_keyspace, protocol_version, result_metadata):

if not column_metadata:

return PreparedStatement(column_metadata, query_id, None, query, prepared_keyspace, protocol_version, result_metadata)

if pk_indexes:

routing_key_indexes = pk_indexes

else:

routing_key_indexes = None

first_col = column_metadata[0]

ks_meta = cluster_metadata.keyspaces.get(first_col.keyspace_name)

if ks_meta:

table_meta = ks_meta.tables.get(first_col.table_name)

if table_meta:

partition_key_columns = table_meta.partition_key

# make a map of {column_name: index} for each column in the statement

statement_indexes = dict((c.name, i) for i, c in enumerate(column_metadata))

# a list of which indexes in the statement correspond to partition key items

try:

routing_key_indexes = [statement_indexes[c.name]

for c in partition_key_columns]

except KeyError: # we're missing a partition key component in the prepared

pass # statement; just leave routing_key_indexes as None

return PreparedStatement(column_metadata, query_id, routing_key_indexes,

query, prepared_keyspace, protocol_version, result_metadata)

def bind(self, values):

"""

Creates and returns a :class:`BoundStatement` instance using `values`.

See :meth:`BoundStatement.bind` for rules on input ``values``.

"""

return BoundStatement(self).bind(values)

def is_routing_key_index(self, i):

if self._routing_key_index_set is None:

self._routing_key_index_set = set(self.routing_key_indexes) if self.routing_key_indexes else set()

return i in self._routing_key_index_set

def __str__(self):

consistency = ConsistencyLevel.value_to_name.get(self.consistency_level, 'Not Set')

return (u'<PreparedStatement query="%s", consistency=%s>' %

(self.query_string, consistency))

__repr__ = __str__

class BoundStatement(Statement):

"""

A prepared statement that has been bound to a particular set of values.

These may be created directly or through :meth:`.PreparedStatement.bind()`.

"""

prepared_statement = None

"""

The :class:`PreparedStatement` instance that this was created from.

"""

values = None

"""

The sequence of values that were bound to the prepared statement.

"""

def __init__(self, prepared_statement, retry_policy=None, consistency_level=None, routing_key=None,

serial_consistency_level=None, fetch_size=FETCH_SIZE_UNSET, keyspace=None,

custom_payload=None):

"""

`prepared_statement` should be an instance of :class:`PreparedStatement`.

See :class:`Statement` attributes for a description of the other parameters.

"""

self.prepared_statement = prepared_statement

self.consistency_level = prepared_statement.consistency_level

self.serial_consistency_level = prepared_statement.serial_consistency_level

self.fetch_size = prepared_statement.fetch_size

self.custom_payload = prepared_statement.custom_payload

self.is_idempotent = prepared_statement.is_idempotent

self.values = []

meta = prepared_statement.column_metadata

if meta:

self.keyspace = meta[0].keyspace_name

Statement.__init__(self, retry_policy, consistency_level, routing_key,

serial_consistency_level, fetch_size, keyspace, custom_payload)

def bind(self, values):

"""

Binds a sequence of values for the prepared statement parameters

and returns this instance. Note that `values` *must* be:

* a sequence, even if you are only binding one value, or

* a dict that relates 1-to-1 between dict keys and columns

.. versionchanged:: 2.6.0

:data:`~.UNSET_VALUE` was introduced. These can be bound as positional parameters

in a sequence, or by name in a dict. Additionally, when using protocol v4+:

* short sequences will be extended to match bind parameters with UNSET_VALUE

* names may be omitted from a dict with UNSET_VALUE implied.

.. versionchanged:: 3.0.0

method will not throw if extra keys are present in bound dict (PYTHON-178)

"""

if values is None:

values = ()

proto_version = self.prepared_statement.protocol_version

col_meta = self.prepared_statement.column_metadata

# special case for binding dicts

if isinstance(values, dict):

values_dict = values

values = []

# sort values accordingly

for col in col_meta:

try:

values.append(values_dict[col.name])

except KeyError:

if proto_version >= 4:

values.append(UNSET_VALUE)

else:

raise KeyError(

'Column name `%s` not found in bound dict.' %

(col.name))

value_len = len(values)

col_meta_len = len(col_meta)

if value_len > col_meta_len:

raise ValueError(

"Too many arguments provided to bind() (got %d, expected %d)" %

(len(values), len(col_meta)))

# this is fail-fast for clarity pre-v4. When v4 can be assumed,

# the error will be better reported when UNSET_VALUE is implicitly added.

if proto_version < 4 and self.prepared_statement.routing_key_indexes and \

value_len < len(self.prepared_statement.routing_key_indexes):

raise ValueError(

"Too few arguments provided to bind() (got %d, required %d for routing key)" %

(value_len, len(self.prepared_statement.routing_key_indexes)))

self.raw_values = values

self.values = []

for value, col_spec in zip(values, col_meta):

if value is None:

self.values.append(None)

elif value is UNSET_VALUE:

if proto_version >= 4:

self._append_unset_value()

else:

raise ValueError("Attempt to bind UNSET_VALUE while using unsuitable protocol version (%d < 4)" % proto_version)

else:

try:

self.values.append(col_spec.type.serialize(value, proto_version))

except (TypeError, struct.error) as exc:

actual_type = type(value)

message = ('Received an argument of invalid type for column "%s". '

'Expected: %s, Got: %s; (%s)' % (col_spec.name, col_spec.type, actual_type, exc))

raise TypeError(message)

if proto_version >= 4:

diff = col_meta_len - len(self.values)

if diff:

for _ in range(diff):

self._append_unset_value()

return self

def _append_unset_value(self):

next_index = len(self.values)

if self.prepared_statement.is_routing_key_index(next_index):

col_meta = self.prepared_statement.column_metadata[next_index]

raise ValueError("Cannot bind UNSET_VALUE as a part of the routing key '%s'" % col_meta.name)

self.values.append(UNSET_VALUE)

@property

def routing_key(self):

if not self.prepared_statement.routing_key_indexes:

return None

if self._routing_key is not None:

return self._routing_key

routing_indexes = self.prepared_statement.routing_key_indexes

if len(routing_indexes) == 1:

self._routing_key = self.values[routing_indexes[0]]

else:

self._routing_key = b"".join(self._key_parts_packed(self.values[i] for i in routing_indexes))

return self._routing_key

def __str__(self):

consistency = ConsistencyLevel.value_to_name.get(self.consistency_level, 'Not Set')

return (u'<BoundStatement query="%s", values=%s, consistency=%s>' %

(self.prepared_statement.query_string, self.raw_values, consistency))

__repr__ = __str__

class BatchType(object):

"""

A BatchType is used with :class:`.BatchStatement` instances to control

the atomicity of the batch operation.

.. versionadded:: 2.0.0

"""

LOGGED = None

"""

Atomic batch operation.

"""

UNLOGGED = None

"""

Non-atomic batch operation.

"""

COUNTER = None

"""

Batches of counter operations.

"""

def __init__(self, name, value):

self.name = name

self.value = value

def __str__(self):

return self.name

def __repr__(self):

return "BatchType.%s" % (self.name, )

BatchType.LOGGED = BatchType("LOGGED", 0)

BatchType.UNLOGGED = BatchType("UNLOGGED", 1)

BatchType.COUNTER = BatchType("COUNTER", 2)

class BatchStatement(Statement):

"""

A protocol-level batch of operations which are applied atomically

by default.

.. versionadded:: 2.0.0

"""

batch_type = None

"""

The :class:`.BatchType` for the batch operation. Defaults to

:attr:`.BatchType.LOGGED`.

"""

serial_consistency_level = None

"""

The same as :attr:`.Statement.serial_consistency_level`.

"""

_statements_and_parameters = None

_session = None

def __init__(self, batch_type=BatchType.LOGGED, retry_policy=None,

consistency_level=None, serial_consistency_level=None,

session=None, custom_payload=None):

"""

`batch_type` specifies The :class:`.BatchType` for the batch operation.

Defaults to :attr:`.BatchType.LOGGED`.

`retry_policy` should be a :class:`~.RetryPolicy` instance for

controlling retries on the operation.

`consistency_level` should be a :class:`~.ConsistencyLevel` value

to be used for all operations in the batch.

`custom_payload` is a :ref:`custom_payload` passed to the server.

Note: as Statement objects are added to the batch, this map is

updated with any values found in their custom payloads. These are

only allowed when using protocol version 4 or higher.

Example usage:

.. code-block:: python

insert_user = session.prepare("INSERT INTO users (name, age) VALUES (?, ?)")

batch = BatchStatement(consistency_level=ConsistencyLevel.QUORUM)

for (name, age) in users_to_insert:

batch.add(insert_user, (name, age))

session.execute(batch)

You can also mix different types of operations within a batch:

.. code-block:: python

batch = BatchStatement()

batch.add(SimpleStatement("INSERT INTO users (name, age) VALUES (%s, %s)"), (name, age))

batch.add(SimpleStatement("DELETE FROM pending_users WHERE name=%s"), (name,))

session.execute(batch)

.. versionadded:: 2.0.0

.. versionchanged:: 2.1.0

Added `serial_consistency_level` as a parameter

.. versionchanged:: 2.6.0

Added `custom_payload` as a parameter

"""

self.batch_type = batch_type

self._statements_and_parameters = []

self._session = session

Statement.__init__(self, retry_policy=retry_policy, consistency_level=consistency_level,

serial_consistency_level=serial_consistency_level, custom_payload=custom_payload)

def clear(self):

"""

This is a convenience method to clear a batch statement for reuse.

*Note:* it should not be used concurrently with uncompleted execution futures executing the same

``BatchStatement``.

"""

del self._statements_and_parameters[:]

self.keyspace = None

self.routing_key = None

if self.custom_payload:

self.custom_payload.clear()

def add(self, statement, parameters=None):

"""

Adds a :class:`.Statement` and optional sequence of parameters

to be used with the statement to the batch.

Like with other statements, parameters must be a sequence, even

if there is only one item.

"""

if isinstance(statement, six.string_types):

if parameters:

encoder = Encoder() if self._session is None else self._session.encoder

statement = bind_params(statement, parameters, encoder)

self._add_statement_and_params(False, statement, ())

elif isinstance(statement, PreparedStatement):

query_id = statement.query_id

bound_statement = statement.bind(() if parameters is None else parameters)

self._update_state(bound_statement)

self._add_statement_and_params(True, query_id, bound_statement.values)

elif isinstance(statement, BoundStatement):

if parameters:

raise ValueError(

"Parameters cannot be passed with a BoundStatement "

"to BatchStatement.add()")

self._update_state(statement)

self._add_statement_and_params(True, statement.prepared_statement.query_id, statement.values)

else:

# it must be a SimpleStatement

query_string = statement.query_string

if parameters:

encoder = Encoder() if self._session is None else self._session.encoder

query_string = bind_params(query_string, parameters, encoder)

self._update_state(statement)

self._add_statement_and_params(False, query_string, ())

return self

def add_all(self, statements, parameters):

"""

Adds a sequence of :class:`.Statement` objects and a matching sequence

of parameters to the batch. Statement and parameter sequences must be of equal length or

one will be truncated. :const:`None` can be used in the parameters position where are needed.

"""

for statement, value in zip(statements, parameters):

self.add(statement, value)

def _add_statement_and_params(self, is_prepared, statement, parameters):

if len(self._statements_and_parameters) >= 0xFFFF:

raise ValueError("Batch statement cannot contain more than %d statements." % 0xFFFF)

self._statements_and_parameters.append((is_prepared, statement, parameters))

def _maybe_set_routing_attributes(self, statement):

if self.routing_key is None:

if statement.keyspace and statement.routing_key:

self.routing_key = statement.routing_key

self.keyspace = statement.keyspace

def _update_custom_payload(self, statement):

if statement.custom_payload:

if self.custom_payload is None:

self.custom_payload = {}

self.custom_payload.update(statement.custom_payload)

def _update_state(self, statement):

self._maybe_set_routing_attributes(statement)

self._update_custom_payload(statement)

def __len__(self):

return len(self._statements_and_parameters)

def __str__(self):

consistency = ConsistencyLevel.value_to_name.get(self.consistency_level, 'Not Set')

return (u'<BatchStatement type=%s, statements=%d, consistency=%s>' %

(self.batch_type, len(self), consistency))

__repr__ = __str__

ValueSequence = cassandra.encoder.ValueSequence

"""

A wrapper class that is used to specify that a sequence of values should

be treated as a CQL list of values instead of a single column collection when used

as part of the `parameters` argument for :meth:`.Session.execute()`.

This is typically needed when supplying a list of keys to select.

For example::

>>> my_user_ids = ('alice', 'bob', 'charles')

>>> query = "SELECT * FROM users WHERE user_id IN %s"

>>> session.execute(query, parameters=[ValueSequence(my_user_ids)])

"""

def bind_params(query, params, encoder):

if six.PY2 and isinstance(query, six.text_type):

query = query.encode('utf-8')

if isinstance(params, dict):

return query % dict((k, encoder.cql_encode_all_types(v)) for k, v in six.iteritems(params))

else:

return query % tuple(encoder.cql_encode_all_types(v) for v in params)

class TraceUnavailable(Exception):

"""

Raised when complete trace details cannot be fetched from Cassandra.

"""

pass

class QueryTrace(object):

"""

A trace of the duration and events that occurred when executing

an operation.

"""

trace_id = None

"""

:class:`uuid.UUID` unique identifier for this tracing session. Matches

the ``session_id`` column in ``system_traces.sessions`` and

``system_traces.events``.

"""

request_type = None

"""

A string that very generally describes the traced operation.

"""

duration = None

"""

A :class:`datetime.timedelta` measure of the duration of the query.

"""

client = None

"""

The IP address of the client that issued this request

This is only available when using Cassandra 2.2+

"""

coordinator = None

"""

The IP address of the host that acted as coordinator for this request.

"""

parameters = None

"""

A :class:`dict` of parameters for the traced operation, such as the

specific query string.

"""

started_at = None

"""

A UTC :class:`datetime.datetime` object describing when the operation

was started.

"""

events = None

"""

A chronologically sorted list of :class:`.TraceEvent` instances

representing the steps the traced operation went through. This

corresponds to the rows in ``system_traces.events`` for this tracing

session.

"""

_session = None

_SELECT_SESSIONS_FORMAT = "SELECT * FROM system_traces.sessions WHERE session_id = %s"

_SELECT_EVENTS_FORMAT = "SELECT * FROM system_traces.events WHERE session_id = %s"

_BASE_RETRY_SLEEP = 0.003

def __init__(self, trace_id, session):

self.trace_id = trace_id

self._session = session

def populate(self, max_wait=2.0, wait_for_complete=True, query_cl=None):

"""

Retrieves the actual tracing details from Cassandra and populates the

attributes of this instance. Because tracing details are stored

asynchronously by Cassandra, this may need to retry the session

detail fetch. If the trace is still not available after `max_wait`

seconds, :exc:`.TraceUnavailable` will be raised; if `max_wait` is

:const:`None`, this will retry forever.

`wait_for_complete=False` bypasses the wait for duration to be populated.

This can be used to query events from partial sessions.

`query_cl` specifies a consistency level to use for polling the trace tables,

if it should be different than the session default.

"""

attempt = 0

start = time.time()

while True:

time_spent = time.time() - start

if max_wait is not None and time_spent >= max_wait:

raise TraceUnavailable(

"Trace information was not available within %f seconds. Consider raising Session.max_trace_wait." % (max_wait,))

log.debug("Attempting to fetch trace info for trace ID: %s", self.trace_id)

session_results = self._execute(

SimpleStatement(self._SELECT_SESSIONS_FORMAT, consistency_level=query_cl), (self.trace_id,), time_spent, max_wait)

is_complete = session_results and session_results[0].duration is not None

if not session_results or (wait_for_complete and not is_complete):

time.sleep(self._BASE_RETRY_SLEEP * (2 ** attempt))

attempt += 1

continue

if is_complete:

log.debug("Fetched trace info for trace ID: %s", self.trace_id)

else:

log.debug("Fetching parital trace info for trace ID: %s", self.trace_id)

session_row = session_results[0]

self.request_type = session_row.request

self.duration = timedelta(microseconds=session_row.duration) if is_complete else None

self.started_at = session_row.started_at

self.coordinator = session_row.coordinator

self.parameters = session_row.parameters

# since C* 2.2

self.client = getattr(session_row, 'client', None)

log.debug("Attempting to fetch trace events for trace ID: %s", self.trace_id)

time_spent = time.time() - start

event_results = self._execute(

SimpleStatement(self._SELECT_EVENTS_FORMAT, consistency_level=query_cl), (self.trace_id,), time_spent, max_wait)

log.debug("Fetched trace events for trace ID: %s", self.trace_id)

self.events = tuple(TraceEvent(r.activity, r.event_id, r.source, r.source_elapsed, r.thread)

for r in event_results)

break

def _execute(self, query, parameters, time_spent, max_wait):

timeout = (max_wait - time_spent) if max_wait is not None else None

future = self._session._create_response_future(query, parameters, trace=False, custom_payload=None, timeout=timeout)

# in case the user switched the row factory, set it to namedtuple for this query

future.row_factory = named_tuple_factory

future.send_request()

try:

return future.result()

except OperationTimedOut:

raise TraceUnavailable("Trace information was not available within %f seconds" % (max_wait,))

def __str__(self):

return "%s [%s] coordinator: %s, started at: %s, duration: %s, parameters: %s" \

% (self.request_type, self.trace_id, self.coordinator, self.started_at,

self.duration, self.parameters)

class TraceEvent(object):

"""

Representation of a single event within a query trace.

"""

description = None

"""

A brief description of the event.

"""

datetime = None

"""

A UTC :class:`datetime.datetime` marking when the event occurred.

"""

source = None

"""

The IP address of the node this event occurred on.

"""

source_elapsed = None

"""

A :class:`datetime.timedelta` measuring the amount of time until

this event occurred starting from when :attr:`.source` first

received the query.

"""

thread_name = None

"""

The name of the thread that this event occurred on.

"""

def __init__(self, description, timeuuid, source, source_elapsed, thread_name):

self.description = description