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Diffstat (limited to 'u1db/__init__.py')
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diff --git a/u1db/__init__.py b/u1db/__init__.py new file mode 100644 index 00000000..ed41bb03 --- /dev/null +++ b/u1db/__init__.py @@ -0,0 +1,697 @@ +# Copyright 2011 Canonical Ltd. +# +# This file is part of u1db. +# +# u1db is free software: you can redistribute it and/or modify +# it under the terms of the GNU Lesser General Public License version 3 +# as published by the Free Software Foundation. +# +# u1db is distributed in the hope that it will be useful, +# but WITHOUT ANY WARRANTY; without even the implied warranty of +# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the +# GNU Lesser General Public License for more details. +# +# You should have received a copy of the GNU Lesser General Public License +# along with u1db. If not, see <http://www.gnu.org/licenses/>. + +"""U1DB""" + +try: + import simplejson as json +except ImportError: + import json # noqa + +from u1db.errors import InvalidJSON, InvalidContent + +__version_info__ = (0, 1, 4) +__version__ = '.'.join(map(str, __version_info__)) + + +def open(path, create, document_factory=None): + """Open a database at the given location. + + Will raise u1db.errors.DatabaseDoesNotExist if create=False and the + database does not already exist. + + :param path: The filesystem path for the database to open. + :param create: True/False, should the database be created if it doesn't + already exist? + :param document_factory: A function that will be called with the same + parameters as Document.__init__. + :return: An instance of Database. + """ + from u1db.backends import sqlite_backend + return sqlite_backend.SQLiteDatabase.open_database( + path, create=create, document_factory=document_factory) + + +# constraints on database names (relevant for remote access, as regex) +DBNAME_CONSTRAINTS = r"[a-zA-Z0-9][a-zA-Z0-9.-]*" + +# constraints on doc ids (as regex) +# (no slashes, and no characters outside the ascii range) +DOC_ID_CONSTRAINTS = r"[a-zA-Z0-9.%_-]+" + + +class Database(object): + """A JSON Document data store. + + This data store can be synchronized with other u1db.Database instances. + """ + + def set_document_factory(self, factory): + """Set the document factory that will be used to create objects to be + returned as documents by the database. + + :param factory: A function that returns an object which at minimum must + satisfy the same interface as does the class DocumentBase. + Subclassing that class is the easiest way to create such + a function. + """ + raise NotImplementedError(self.set_document_factory) + + def set_document_size_limit(self, limit): + """Set the maximum allowed document size for this database. + + :param limit: Maximum allowed document size in bytes. + """ + raise NotImplementedError(self.set_document_size_limit) + + def whats_changed(self, old_generation=0): + """Return a list of documents that have changed since old_generation. + This allows APPS to only store a db generation before going + 'offline', and then when coming back online they can use this + data to update whatever extra data they are storing. + + :param old_generation: The generation of the database in the old + state. + :return: (generation, trans_id, [(doc_id, generation, trans_id),...]) + The current generation of the database, its associated transaction + id, and a list of of changed documents since old_generation, + represented by tuples with for each document its doc_id and the + generation and transaction id corresponding to the last intervening + change and sorted by generation (old changes first) + """ + raise NotImplementedError(self.whats_changed) + + def get_doc(self, doc_id, include_deleted=False): + """Get the JSON string for the given document. + + :param doc_id: The unique document identifier + :param include_deleted: If set to True, deleted documents will be + returned with empty content. Otherwise asking for a deleted + document will return None. + :return: a Document object. + """ + raise NotImplementedError(self.get_doc) + + def get_docs(self, doc_ids, check_for_conflicts=True, + include_deleted=False): + """Get the JSON content for many documents. + + :param doc_ids: A list of document identifiers. + :param check_for_conflicts: If set to False, then the conflict check + will be skipped, and 'None' will be returned instead of True/False. + :param include_deleted: If set to True, deleted documents will be + returned with empty content. Otherwise deleted documents will not + be included in the results. + :return: iterable giving the Document object for each document id + in matching doc_ids order. + """ + raise NotImplementedError(self.get_docs) + + def get_all_docs(self, include_deleted=False): + """Get the JSON content for all documents in the database. + + :param include_deleted: If set to True, deleted documents will be + returned with empty content. Otherwise deleted documents will not + be included in the results. + :return: (generation, [Document]) + The current generation of the database, followed by a list of all + the documents in the database. + """ + raise NotImplementedError(self.get_all_docs) + + def create_doc(self, content, doc_id=None): + """Create a new document. + + You can optionally specify the document identifier, but the document + must not already exist. See 'put_doc' if you want to override an + existing document. + If the database specifies a maximum document size and the document + exceeds it, create will fail and raise a DocumentTooBig exception. + + :param content: A Python dictionary. + :param doc_id: An optional identifier specifying the document id. + :return: Document + """ + raise NotImplementedError(self.create_doc) + + def create_doc_from_json(self, json, doc_id=None): + """Create a new document. + + You can optionally specify the document identifier, but the document + must not already exist. See 'put_doc' if you want to override an + existing document. + If the database specifies a maximum document size and the document + exceeds it, create will fail and raise a DocumentTooBig exception. + + :param json: The JSON document string + :param doc_id: An optional identifier specifying the document id. + :return: Document + """ + raise NotImplementedError(self.create_doc_from_json) + + def put_doc(self, doc): + """Update a document. + If the document currently has conflicts, put will fail. + If the database specifies a maximum document size and the document + exceeds it, put will fail and raise a DocumentTooBig exception. + + :param doc: A Document with new content. + :return: new_doc_rev - The new revision identifier for the document. + The Document object will also be updated. + """ + raise NotImplementedError(self.put_doc) + + def delete_doc(self, doc): + """Mark a document as deleted. + Will abort if the current revision doesn't match doc.rev. + This will also set doc.content to None. + """ + raise NotImplementedError(self.delete_doc) + + def create_index(self, index_name, *index_expressions): + """Create an named index, which can then be queried for future lookups. + Creating an index which already exists is not an error, and is cheap. + Creating an index which does not match the index_expressions of the + existing index is an error. + Creating an index will block until the expressions have been evaluated + and the index generated. + + :param index_name: A unique name which can be used as a key prefix + :param index_expressions: index expressions defining the index + information. + + Examples: + + "fieldname", or "fieldname.subfieldname" to index alphabetically + sorted on the contents of a field. + + "number(fieldname, width)", "lower(fieldname)" + """ + raise NotImplementedError(self.create_index) + + def delete_index(self, index_name): + """Remove a named index. + + :param index_name: The name of the index we are removing + """ + raise NotImplementedError(self.delete_index) + + def list_indexes(self): + """List the definitions of all known indexes. + + :return: A list of [('index-name', ['field', 'field2'])] definitions. + """ + raise NotImplementedError(self.list_indexes) + + def get_from_index(self, index_name, *key_values): + """Return documents that match the keys supplied. + + You must supply exactly the same number of values as have been defined + in the index. It is possible to do a prefix match by using '*' to + indicate a wildcard match. You can only supply '*' to trailing entries, + (eg 'val', '*', '*' is allowed, but '*', 'val', 'val' is not.) + It is also possible to append a '*' to the last supplied value (eg + 'val*', '*', '*' or 'val', 'val*', '*', but not 'val*', 'val', '*') + + :param index_name: The index to query + :param key_values: values to match. eg, if you have + an index with 3 fields then you would have: + get_from_index(index_name, val1, val2, val3) + :return: List of [Document] + """ + raise NotImplementedError(self.get_from_index) + + def get_range_from_index(self, index_name, start_value, end_value): + """Return documents that fall within the specified range. + + Both ends of the range are inclusive. For both start_value and + end_value, one must supply exactly the same number of values as have + been defined in the index, or pass None. In case of a single column + index, a string is accepted as an alternative for a tuple with a single + value. It is possible to do a prefix match by using '*' to indicate + a wildcard match. You can only supply '*' to trailing entries, (eg + 'val', '*', '*' is allowed, but '*', 'val', 'val' is not.) It is also + possible to append a '*' to the last supplied value (eg 'val*', '*', + '*' or 'val', 'val*', '*', but not 'val*', 'val', '*') + + :param index_name: The index to query + :param start_values: tuples of values that define the lower bound of + the range. eg, if you have an index with 3 fields then you would + have: (val1, val2, val3) + :param end_values: tuples of values that define the upper bound of the + range. eg, if you have an index with 3 fields then you would have: + (val1, val2, val3) + :return: List of [Document] + """ + raise NotImplementedError(self.get_range_from_index) + + def get_index_keys(self, index_name): + """Return all keys under which documents are indexed in this index. + + :param index_name: The index to query + :return: [] A list of tuples of indexed keys. + """ + raise NotImplementedError(self.get_index_keys) + + def get_doc_conflicts(self, doc_id): + """Get the list of conflicts for the given document. + + The order of the conflicts is such that the first entry is the value + that would be returned by "get_doc". + + :return: [doc] A list of the Document entries that are conflicted. + """ + raise NotImplementedError(self.get_doc_conflicts) + + def resolve_doc(self, doc, conflicted_doc_revs): + """Mark a document as no longer conflicted. + + We take the list of revisions that the client knows about that it is + superseding. This may be a different list from the actual current + conflicts, in which case only those are removed as conflicted. This + may fail if the conflict list is significantly different from the + supplied information. (sync could have happened in the background from + the time you GET_DOC_CONFLICTS until the point where you RESOLVE) + + :param doc: A Document with the new content to be inserted. + :param conflicted_doc_revs: A list of revisions that the new content + supersedes. + """ + raise NotImplementedError(self.resolve_doc) + + def get_sync_target(self): + """Return a SyncTarget object, for another u1db to synchronize with. + + :return: An instance of SyncTarget. + """ + raise NotImplementedError(self.get_sync_target) + + def close(self): + """Release any resources associated with this database.""" + raise NotImplementedError(self.close) + + def sync(self, url, creds=None, autocreate=True): + """Synchronize documents with remote replica exposed at url. + + :param url: the url of the target replica to sync with. + :param creds: optional dictionary giving credentials + to authorize the operation with the server. For using OAuth + the form of creds is: + {'oauth': { + 'consumer_key': ..., + 'consumer_secret': ..., + 'token_key': ..., + 'token_secret': ... + }} + :param autocreate: ask the target to create the db if non-existent. + :return: local_gen_before_sync The local generation before the + synchronisation was performed. This is useful to pass into + whatschanged, if an application wants to know which documents were + affected by a synchronisation. + """ + from u1db.sync import Synchronizer + from u1db.remote.http_target import HTTPSyncTarget + return Synchronizer(self, HTTPSyncTarget(url, creds=creds)).sync( + autocreate=autocreate) + + def _get_replica_gen_and_trans_id(self, other_replica_uid): + """Return the last known generation and transaction id for the other db + replica. + + When you do a synchronization with another replica, the Database keeps + track of what generation the other database replica was at, and what + the associated transaction id was. This is used to determine what data + needs to be sent, and if two databases are claiming to be the same + replica. + + :param other_replica_uid: The identifier for the other replica. + :return: (gen, trans_id) The generation and transaction id we + encountered during synchronization. If we've never synchronized + with the replica, this is (0, ''). + """ + raise NotImplementedError(self._get_replica_gen_and_trans_id) + + def _set_replica_gen_and_trans_id(self, other_replica_uid, + other_generation, other_transaction_id): + """Set the last-known generation and transaction id for the other + database replica. + + We have just performed some synchronization, and we want to track what + generation the other replica was at. See also + _get_replica_gen_and_trans_id. + :param other_replica_uid: The U1DB identifier for the other replica. + :param other_generation: The generation number for the other replica. + :param other_transaction_id: The transaction id associated with the + generation. + """ + raise NotImplementedError(self._set_replica_gen_and_trans_id) + + def _put_doc_if_newer(self, doc, save_conflict, replica_uid, replica_gen, + replica_trans_id=''): + """Insert/update document into the database with a given revision. + + This api is used during synchronization operations. + + If a document would conflict and save_conflict is set to True, the + content will be selected as the 'current' content for doc.doc_id, + even though doc.rev doesn't supersede the currently stored revision. + The currently stored document will be added to the list of conflict + alternatives for the given doc_id. + + This forces the new content to be 'current' so that we get convergence + after synchronizing, even if people don't resolve conflicts. Users can + then notice that their content is out of date, update it, and + synchronize again. (The alternative is that users could synchronize and + think the data has propagated, but their local copy looks fine, and the + remote copy is never updated again.) + + :param doc: A Document object + :param save_conflict: If this document is a conflict, do you want to + save it as a conflict, or just ignore it. + :param replica_uid: A unique replica identifier. + :param replica_gen: The generation of the replica corresponding to the + this document. The replica arguments are optional, but are used + during synchronization. + :param replica_trans_id: The transaction_id associated with the + generation. + :return: (state, at_gen) - If we don't have doc_id already, + or if doc_rev supersedes the existing document revision, + then the content will be inserted, and state is 'inserted'. + If doc_rev is less than or equal to the existing revision, + then the put is ignored and state is respecitvely 'superseded' + or 'converged'. + If doc_rev is not strictly superseded or supersedes, then + state is 'conflicted'. The document will not be inserted if + save_conflict is False. + For 'inserted' or 'converged', at_gen is the insertion/current + generation. + """ + raise NotImplementedError(self._put_doc_if_newer) + + +class DocumentBase(object): + """Container for handling a single document. + + :ivar doc_id: Unique identifier for this document. + :ivar rev: The revision identifier of the document. + :ivar json_string: The JSON string for this document. + :ivar has_conflicts: Boolean indicating if this document has conflicts + """ + + def __init__(self, doc_id, rev, json_string, has_conflicts=False): + self.doc_id = doc_id + self.rev = rev + if json_string is not None: + try: + value = json.loads(json_string) + except json.JSONDecodeError: + raise InvalidJSON + if not isinstance(value, dict): + raise InvalidJSON + self._json = json_string + self.has_conflicts = has_conflicts + + def same_content_as(self, other): + """Compare the content of two documents.""" + if self._json: + c1 = json.loads(self._json) + else: + c1 = None + if other._json: + c2 = json.loads(other._json) + else: + c2 = None + return c1 == c2 + + def __repr__(self): + if self.has_conflicts: + extra = ', conflicted' + else: + extra = '' + return '%s(%s, %s%s, %r)' % (self.__class__.__name__, self.doc_id, + self.rev, extra, self.get_json()) + + def __hash__(self): + raise NotImplementedError(self.__hash__) + + def __eq__(self, other): + if not isinstance(other, Document): + return NotImplemented + return ( + self.doc_id == other.doc_id and self.rev == other.rev and + self.same_content_as(other) and self.has_conflicts == + other.has_conflicts) + + def __lt__(self, other): + """This is meant for testing, not part of the official api. + + It is implemented so that sorted([Document, Document]) can be used. + It doesn't imply that users would want their documents to be sorted in + this order. + """ + # Since this is just for testing, we don't worry about comparing + # against things that aren't a Document. + return ((self.doc_id, self.rev, self.get_json()) + < (other.doc_id, other.rev, other.get_json())) + + def get_json(self): + """Get the json serialization of this document.""" + if self._json is not None: + return self._json + return None + + def get_size(self): + """Calculate the total size of the document.""" + size = 0 + json = self.get_json() + if json: + size += len(json) + if self.rev: + size += len(self.rev) + if self.doc_id: + size += len(self.doc_id) + return size + + def set_json(self, json_string): + """Set the json serialization of this document.""" + if json_string is not None: + try: + value = json.loads(json_string) + except json.JSONDecodeError: + raise InvalidJSON + if not isinstance(value, dict): + raise InvalidJSON + self._json = json_string + + def make_tombstone(self): + """Make this document into a tombstone.""" + self._json = None + + def is_tombstone(self): + """Return True if the document is a tombstone, False otherwise.""" + if self._json is not None: + return False + return True + + +class Document(DocumentBase): + """Container for handling a single document. + + :ivar doc_id: Unique identifier for this document. + :ivar rev: The revision identifier of the document. + :ivar json: The JSON string for this document. + :ivar has_conflicts: Boolean indicating if this document has conflicts + """ + + # The following part of the API is optional: no implementation is forced to + # have it but if the language supports dictionaries/hashtables, it makes + # Documents a lot more user friendly. + + def __init__(self, doc_id=None, rev=None, json='{}', has_conflicts=False): + # TODO: We convert the json in the superclass to check its validity so + # we might as well set _content here directly since the price is + # already being paid. + super(Document, self).__init__(doc_id, rev, json, has_conflicts) + self._content = None + + def same_content_as(self, other): + """Compare the content of two documents.""" + if self._json: + c1 = json.loads(self._json) + else: + c1 = self._content + if other._json: + c2 = json.loads(other._json) + else: + c2 = other._content + return c1 == c2 + + def get_json(self): + """Get the json serialization of this document.""" + json_string = super(Document, self).get_json() + if json_string is not None: + return json_string + if self._content is not None: + return json.dumps(self._content) + return None + + def set_json(self, json): + """Set the json serialization of this document.""" + self._content = None + super(Document, self).set_json(json) + + def make_tombstone(self): + """Make this document into a tombstone.""" + self._content = None + super(Document, self).make_tombstone() + + def is_tombstone(self): + """Return True if the document is a tombstone, False otherwise.""" + if self._content is not None: + return False + return super(Document, self).is_tombstone() + + def _get_content(self): + """Get the dictionary representing this document.""" + if self._json is not None: + self._content = json.loads(self._json) + self._json = None + if self._content is not None: + return self._content + return None + + def _set_content(self, content): + """Set the dictionary representing this document.""" + try: + tmp = json.dumps(content) + except TypeError: + raise InvalidContent( + "Can not be converted to JSON: %r" % (content,)) + if not tmp.startswith('{'): + raise InvalidContent( + "Can not be converted to a JSON object: %r." % (content,)) + # We might as well store the JSON at this point since we did the work + # of encoding it, and it doesn't lose any information. + self._json = tmp + self._content = None + + content = property( + _get_content, _set_content, doc="Content of the Document.") + + # End of optional part. + + +class SyncTarget(object): + """Functionality for using a Database as a synchronization target.""" + + def get_sync_info(self, source_replica_uid): + """Return information about known state. + + Return the replica_uid and the current database generation of this + database, and the last-seen database generation for source_replica_uid + + :param source_replica_uid: Another replica which we might have + synchronized with in the past. + :return: (target_replica_uid, target_replica_generation, + target_trans_id, source_replica_last_known_generation, + source_replica_last_known_transaction_id) + """ + raise NotImplementedError(self.get_sync_info) + + def record_sync_info(self, source_replica_uid, source_replica_generation, + source_replica_transaction_id): + """Record tip information for another replica. + + After sync_exchange has been processed, the caller will have + received new content from this replica. This call allows the + source replica instigating the sync to inform us what their + generation became after applying the documents we returned. + + This is used to allow future sync operations to not need to repeat data + that we just talked about. It also means that if this is called at the + wrong time, there can be database records that will never be + synchronized. + + :param source_replica_uid: The identifier for the source replica. + :param source_replica_generation: + The database generation for the source replica. + :param source_replica_transaction_id: The transaction id associated + with the source replica generation. + """ + raise NotImplementedError(self.record_sync_info) + + def sync_exchange(self, docs_by_generation, source_replica_uid, + last_known_generation, last_known_trans_id, + return_doc_cb, ensure_callback=None): + """Incorporate the documents sent from the source replica. + + This is not meant to be called by client code directly, but is used as + part of sync(). + + This adds docs to the local store, and determines documents that need + to be returned to the source replica. + + Documents must be supplied in docs_by_generation paired with + the generation of their latest change in order from the oldest + change to the newest, that means from the oldest generation to + the newest. + + Documents are also returned paired with the generation of + their latest change in order from the oldest change to the + newest. + + :param docs_by_generation: A list of [(Document, generation, + transaction_id)] tuples indicating documents which should be + updated on this replica paired with the generation and transaction + id of their latest change. + :param source_replica_uid: The source replica's identifier + :param last_known_generation: The last generation that the source + replica knows about this target replica + :param last_known_trans_id: The last transaction id that the source + replica knows about this target replica + :param: return_doc_cb(doc, gen): is a callback + used to return documents to the source replica, it will + be invoked in turn with Documents that have changed since + last_known_generation together with the generation of + their last change. + :param: ensure_callback(replica_uid): if set the target may create + the target db if not yet existent, the callback can then + be used to inform of the created db replica uid. + :return: new_generation - After applying docs_by_generation, this is + the current generation for this replica + """ + raise NotImplementedError(self.sync_exchange) + + def _set_trace_hook(self, cb): + """Set a callback that will be invoked to trace database actions. + + The callback will be passed a string indicating the current state, and + the sync target object. Implementations do not have to implement this + api, it is used by the test suite. + + :param cb: A callable that takes cb(state) + """ + raise NotImplementedError(self._set_trace_hook) + + def _set_trace_hook_shallow(self, cb): + """Set a callback that will be invoked to trace database actions. + + Similar to _set_trace_hook, for implementations that don't offer + state changes from the inner working of sync_exchange(). + + :param cb: A callable that takes cb(state) + """ + self._set_trace_hook(cb) |