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Diffstat (limited to 'u1db/backends/__init__.py')
| -rw-r--r-- | u1db/backends/__init__.py | 211 |
1 files changed, 211 insertions, 0 deletions
diff --git a/u1db/backends/__init__.py b/u1db/backends/__init__.py new file mode 100644 index 00000000..c8e5adc6 --- /dev/null +++ b/u1db/backends/__init__.py @@ -0,0 +1,211 @@ +# 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/>. + +"""Abstract classes and common implementations for the backends.""" + +import re +try: + import simplejson as json +except ImportError: + import json # noqa +import uuid + +import u1db +from u1db import ( + errors, +) +import u1db.sync +from u1db.vectorclock import VectorClockRev + + +check_doc_id_re = re.compile("^" + u1db.DOC_ID_CONSTRAINTS + "$", re.UNICODE) + + +class CommonSyncTarget(u1db.sync.LocalSyncTarget): + pass + + +class CommonBackend(u1db.Database): + + document_size_limit = 0 + + def _allocate_doc_id(self): + """Generate a unique identifier for this document.""" + return 'D-' + uuid.uuid4().hex # 'D-' stands for document + + def _allocate_transaction_id(self): + return 'T-' + uuid.uuid4().hex # 'T-' stands for transaction + + def _allocate_doc_rev(self, old_doc_rev): + vcr = VectorClockRev(old_doc_rev) + vcr.increment(self._replica_uid) + return vcr.as_str() + + def _check_doc_id(self, doc_id): + if not check_doc_id_re.match(doc_id): + raise errors.InvalidDocId() + + def _check_doc_size(self, doc): + if not self.document_size_limit: + return + if doc.get_size() > self.document_size_limit: + raise errors.DocumentTooBig + + def _get_generation(self): + """Return the current generation. + + """ + raise NotImplementedError(self._get_generation) + + def _get_generation_info(self): + """Return the current generation and transaction id. + + """ + raise NotImplementedError(self._get_generation_info) + + def _get_doc(self, doc_id, check_for_conflicts=False): + """Extract the document from storage. + + This can return None if the document doesn't exist. + """ + raise NotImplementedError(self._get_doc) + + def _has_conflicts(self, doc_id): + """Return True if the doc has conflicts, False otherwise.""" + raise NotImplementedError(self._has_conflicts) + + def create_doc(self, content, doc_id=None): + json_string = json.dumps(content) + if doc_id is None: + doc_id = self._allocate_doc_id() + doc = self._factory(doc_id, None, json_string) + self.put_doc(doc) + return doc + + def create_doc_from_json(self, json, doc_id=None): + if doc_id is None: + doc_id = self._allocate_doc_id() + doc = self._factory(doc_id, None, json) + self.put_doc(doc) + return doc + + def _get_transaction_log(self): + """This is only for the test suite, it is not part of the api.""" + raise NotImplementedError(self._get_transaction_log) + + def _put_and_update_indexes(self, doc_id, old_doc, new_rev, content): + raise NotImplementedError(self._put_and_update_indexes) + + def get_docs(self, doc_ids, check_for_conflicts=True, + include_deleted=False): + for doc_id in doc_ids: + doc = self._get_doc( + doc_id, check_for_conflicts=check_for_conflicts) + if doc.is_tombstone() and not include_deleted: + continue + yield doc + + def _get_trans_id_for_gen(self, generation): + """Get the transaction id corresponding to a particular generation. + + Raises an InvalidGeneration when the generation does not exist. + + """ + raise NotImplementedError(self._get_trans_id_for_gen) + + def validate_gen_and_trans_id(self, generation, trans_id): + """Validate the generation and transaction id. + + Raises an InvalidGeneration when the generation does not exist, and an + InvalidTransactionId when it does but with a different transaction id. + + """ + if generation == 0: + return + known_trans_id = self._get_trans_id_for_gen(generation) + if known_trans_id != trans_id: + raise errors.InvalidTransactionId + + def _validate_source(self, other_replica_uid, other_generation, + other_transaction_id): + """Validate the new generation and transaction id. + + other_generation must be greater than what we have stored for this + replica, *or* it must be the same and the transaction_id must be the + same as well. + """ + (old_generation, + old_transaction_id) = self._get_replica_gen_and_trans_id( + other_replica_uid) + if other_generation < old_generation: + raise errors.InvalidGeneration + if other_generation > old_generation: + return + if other_transaction_id == old_transaction_id: + return + raise errors.InvalidTransactionId + + def _put_doc_if_newer(self, doc, save_conflict, replica_uid, replica_gen, + replica_trans_id=''): + cur_doc = self._get_doc(doc.doc_id) + doc_vcr = VectorClockRev(doc.rev) + if cur_doc is None: + cur_vcr = VectorClockRev(None) + else: + cur_vcr = VectorClockRev(cur_doc.rev) + self._validate_source(replica_uid, replica_gen, replica_trans_id) + if doc_vcr.is_newer(cur_vcr): + rev = doc.rev + self._prune_conflicts(doc, doc_vcr) + if doc.rev != rev: + # conflicts have been autoresolved + state = 'superseded' + else: + state = 'inserted' + self._put_and_update_indexes(cur_doc, doc) + elif doc.rev == cur_doc.rev: + # magical convergence + state = 'converged' + elif cur_vcr.is_newer(doc_vcr): + # Don't add this to seen_ids, because we have something newer, + # so we should send it back, and we should not generate a + # conflict + state = 'superseded' + elif cur_doc.same_content_as(doc): + # the documents have been edited to the same thing at both ends + doc_vcr.maximize(cur_vcr) + doc_vcr.increment(self._replica_uid) + doc.rev = doc_vcr.as_str() + self._put_and_update_indexes(cur_doc, doc) + state = 'superseded' + else: + state = 'conflicted' + if save_conflict: + self._force_doc_sync_conflict(doc) + if replica_uid is not None and replica_gen is not None: + self._do_set_replica_gen_and_trans_id( + replica_uid, replica_gen, replica_trans_id) + return state, self._get_generation() + + def _ensure_maximal_rev(self, cur_rev, extra_revs): + vcr = VectorClockRev(cur_rev) + for rev in extra_revs: + vcr.maximize(VectorClockRev(rev)) + vcr.increment(self._replica_uid) + return vcr.as_str() + + def set_document_size_limit(self, limit): + self.document_size_limit = limit |