Source code for couchbase.mutation_state

# Copyright 2017, Couchbase, Inc.
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# Licensed under the Apache License, Version 2.0 (the "License")
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# distributed under the License is distributed on an "AS IS" BASIS,
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from couchbase.exceptions import CouchbaseException
from couchbase_core import _from_json, _to_json

class MissingTokenException(CouchbaseException):

[docs]class MutationState(object): """ .. warning:: The API and implementation of this class are subject to change. This class acts as a container for one or more mutations. It may then be used with the :meth:`~._N1QLQuery.consistent_with` method to indicate that a given query should be bounded by the contained mutations. Using `consistent_with` is similar to setting :attr:`~._N1QLQuery.consistency` to :data:`REQUEST_PLUS`, but is more optimal as the query will use cached data, *except* when the given mutation(s) are concerned. This option is useful for use patterns when an application has just performed a mutation, and wishes to perform a query in which the newly-performed mutation should reflect on the query results. .. note:: This feature requires Couchbase Server 4.5 or greater, and is enabled by default with 3.x SDKs. To disable, set the enable_mutation_tokens option in the :class:`couchbase.cluster.ClusterOptions` to False .. code-block:: python cluster = Cluster('couchbase://localhost', authenticator=PasswordAuthenticator('Administrator', 'password')) bucket = cluster.bucket('default') collection = bucket.default_collection() rv = collection.upsert('foo': {'type': 'user', 'value': 'a foo value'}) ms = MutationState(res) q_opts = QueryOptions(consistent_with=ms) q_str = 'SELECT type, value FROM default WHERE type="user"' query_iter = cluster.query(q_str, q_opts) for row in query_iter.rows(): # ... """ def __init__(self, *docs): self._sv = {} if docs: self.add_results(*docs) def _add_scanvec(self, mutinfo): """ Internal method used to specify a scan vector. :param mutinfo: A tuple in the form of `(vbucket id, vbucket uuid, mutation sequence)` """ vb, uuid, seq, bktname = mutinfo self._sv.setdefault(bktname, {})[vb] = (seq, str(uuid)) def encode(self): """ Encodes this state object to a string. This string may be passed to the :meth:`decode` at a later time. The returned object is safe for sending over the network. :return: A serialized string representing the state """ return _to_json(self._sv) def _to_fts_encodable(self): if len(self._sv) > 1: raise TypeError('Cannot use more than a single bucket with F.T.S.') from couchbase_core._pyport import single_dict_key out = {} for vb, params in self._sv[single_dict_key(self._sv)].items(): out['{0}/{1}'.format(vb, params[1])] = params[0] return out @classmethod def decode(cls, s): """ Create a :class:`MutationState` from the encoded string :param s: The encoded string :return: A new MutationState restored from the string """ d = _from_json(s) o = MutationState() o._sv = d # TODO: Validate def add_results(self, *rvs, **kwargs): """ Changes the state to reflect the mutation which yielded the given result. In order to use the result, the `enable_mutation_tokens` option must have been specified in the connection string, _and_ the result must have been successful. :param rvs: One or more :class:`~.OperationResult` which have been returned from mutations :param quiet: Suppress errors if one of the results does not contain a convertible state. :return: `True` if the result was valid and added, `False` if not added (and `quiet` was specified :raise: :exc:`~.MissingTokenException` if `result` does not contain a valid token """ if not rvs: raise MissingTokenException.pyexc(message='No results passed') for rv in rvs: mi = rv.mutation_token().as_tuple() if not mi: if kwargs.get('quiet'): return False raise MissingTokenException.pyexc( message='Result does not contain token') self._add_scanvec(mi) return True def add_all(self, bucket, quiet=False): """ Ensures the query result is consistent with all prior mutations performed by a given bucket. Using this function is equivalent to keeping track of all mutations performed by the given bucket, and passing them to :meth:`~add_result` :param bucket: A :class:`~couchbase_core.client.Client` object used for the mutations :param quiet: If the bucket contains no valid mutations, this option suppresses throwing exceptions. :return: `True` if at least one mutation was added, `False` if none were added (and `quiet` was specified) :raise: :exc:`~.MissingTokenException` if no mutations were added and `quiet` was not specified """ added = False for mt in bucket._mutinfo(): added = True self._add_scanvec(mt) if not added and not quiet: raise MissingTokenException('Bucket object contains no tokens!') return added def __repr__(self): return repr(self._sv) def __nonzero__(self): return bool(self._sv) __bool__ = __nonzero__