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Diffstat (limited to 'u1db/backends/inmemory.py')
| -rw-r--r-- | u1db/backends/inmemory.py | 469 |
1 files changed, 469 insertions, 0 deletions
diff --git a/u1db/backends/inmemory.py b/u1db/backends/inmemory.py new file mode 100644 index 00000000..a271bb37 --- /dev/null +++ b/u1db/backends/inmemory.py @@ -0,0 +1,469 @@ +# 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/>. + +"""The in-memory Database class for U1DB.""" + +try: + import simplejson as json +except ImportError: + import json # noqa + +from u1db import ( + Document, + errors, + query_parser, + vectorclock, + ) +from u1db.backends import CommonBackend, CommonSyncTarget + + +def get_prefix(value): + key_prefix = '\x01'.join(value) + return key_prefix.rstrip('*') + + +class InMemoryDatabase(CommonBackend): + """A database that only stores the data internally.""" + + def __init__(self, replica_uid, document_factory=None): + self._transaction_log = [] + self._docs = {} + # Map from doc_id => [(doc_rev, doc)] conflicts beyond 'winner' + self._conflicts = {} + self._other_generations = {} + self._indexes = {} + self._replica_uid = replica_uid + self._factory = document_factory or Document + + def _set_replica_uid(self, replica_uid): + """Force the replica_uid to be set.""" + self._replica_uid = replica_uid + + def set_document_factory(self, factory): + self._factory = factory + + def close(self): + # This is a no-op, We don't want to free the data because one client + # may be closing it, while another wants to inspect the results. + pass + + def _get_replica_gen_and_trans_id(self, other_replica_uid): + return self._other_generations.get(other_replica_uid, (0, '')) + + def _set_replica_gen_and_trans_id(self, other_replica_uid, + other_generation, other_transaction_id): + self._do_set_replica_gen_and_trans_id( + other_replica_uid, other_generation, other_transaction_id) + + def _do_set_replica_gen_and_trans_id(self, other_replica_uid, + other_generation, + other_transaction_id): + # TODO: to handle race conditions, we may want to check if the current + # value is greater than this new value. + self._other_generations[other_replica_uid] = (other_generation, + other_transaction_id) + + def get_sync_target(self): + return InMemorySyncTarget(self) + + def _get_transaction_log(self): + # snapshot! + return self._transaction_log[:] + + def _get_generation(self): + return len(self._transaction_log) + + def _get_generation_info(self): + if not self._transaction_log: + return 0, '' + return len(self._transaction_log), self._transaction_log[-1][1] + + def _get_trans_id_for_gen(self, generation): + if generation == 0: + return '' + if generation > len(self._transaction_log): + raise errors.InvalidGeneration + return self._transaction_log[generation - 1][1] + + def put_doc(self, doc): + if doc.doc_id is None: + raise errors.InvalidDocId() + self._check_doc_id(doc.doc_id) + self._check_doc_size(doc) + old_doc = self._get_doc(doc.doc_id, check_for_conflicts=True) + if old_doc and old_doc.has_conflicts: + raise errors.ConflictedDoc() + if old_doc and doc.rev is None and old_doc.is_tombstone(): + new_rev = self._allocate_doc_rev(old_doc.rev) + else: + if old_doc is not None: + if old_doc.rev != doc.rev: + raise errors.RevisionConflict() + else: + if doc.rev is not None: + raise errors.RevisionConflict() + new_rev = self._allocate_doc_rev(doc.rev) + doc.rev = new_rev + self._put_and_update_indexes(old_doc, doc) + return new_rev + + def _put_and_update_indexes(self, old_doc, doc): + for index in self._indexes.itervalues(): + if old_doc is not None and not old_doc.is_tombstone(): + index.remove_json(old_doc.doc_id, old_doc.get_json()) + if not doc.is_tombstone(): + index.add_json(doc.doc_id, doc.get_json()) + trans_id = self._allocate_transaction_id() + self._docs[doc.doc_id] = (doc.rev, doc.get_json()) + self._transaction_log.append((doc.doc_id, trans_id)) + + def _get_doc(self, doc_id, check_for_conflicts=False): + try: + doc_rev, content = self._docs[doc_id] + except KeyError: + return None + doc = self._factory(doc_id, doc_rev, content) + if check_for_conflicts: + doc.has_conflicts = (doc.doc_id in self._conflicts) + return doc + + def _has_conflicts(self, doc_id): + return doc_id in self._conflicts + + def get_doc(self, doc_id, include_deleted=False): + doc = self._get_doc(doc_id, check_for_conflicts=True) + if doc is None: + return None + if doc.is_tombstone() and not include_deleted: + return None + return doc + + def get_all_docs(self, include_deleted=False): + """Return all documents in the database.""" + generation = self._get_generation() + results = [] + for doc_id, (doc_rev, content) in self._docs.items(): + if content is None and not include_deleted: + continue + doc = self._factory(doc_id, doc_rev, content) + doc.has_conflicts = self._has_conflicts(doc_id) + results.append(doc) + return (generation, results) + + def get_doc_conflicts(self, doc_id): + if doc_id not in self._conflicts: + return [] + result = [self._get_doc(doc_id)] + result[0].has_conflicts = True + result.extend([self._factory(doc_id, rev, content) + for rev, content in self._conflicts[doc_id]]) + return result + + def _replace_conflicts(self, doc, conflicts): + if not conflicts: + del self._conflicts[doc.doc_id] + else: + self._conflicts[doc.doc_id] = conflicts + doc.has_conflicts = bool(conflicts) + + def _prune_conflicts(self, doc, doc_vcr): + if self._has_conflicts(doc.doc_id): + autoresolved = False + remaining_conflicts = [] + cur_conflicts = self._conflicts[doc.doc_id] + for c_rev, c_doc in cur_conflicts: + c_vcr = vectorclock.VectorClockRev(c_rev) + if doc_vcr.is_newer(c_vcr): + continue + if doc.same_content_as(Document(doc.doc_id, c_rev, c_doc)): + doc_vcr.maximize(c_vcr) + autoresolved = True + continue + remaining_conflicts.append((c_rev, c_doc)) + if autoresolved: + doc_vcr.increment(self._replica_uid) + doc.rev = doc_vcr.as_str() + self._replace_conflicts(doc, remaining_conflicts) + + def resolve_doc(self, doc, conflicted_doc_revs): + cur_doc = self._get_doc(doc.doc_id) + if cur_doc is None: + cur_rev = None + else: + cur_rev = cur_doc.rev + new_rev = self._ensure_maximal_rev(cur_rev, conflicted_doc_revs) + superseded_revs = set(conflicted_doc_revs) + remaining_conflicts = [] + cur_conflicts = self._conflicts[doc.doc_id] + for c_rev, c_doc in cur_conflicts: + if c_rev in superseded_revs: + continue + remaining_conflicts.append((c_rev, c_doc)) + doc.rev = new_rev + if cur_rev in superseded_revs: + self._put_and_update_indexes(cur_doc, doc) + else: + remaining_conflicts.append((new_rev, doc.get_json())) + self._replace_conflicts(doc, remaining_conflicts) + + def delete_doc(self, doc): + if doc.doc_id not in self._docs: + raise errors.DocumentDoesNotExist + if self._docs[doc.doc_id][1] in ('null', None): + raise errors.DocumentAlreadyDeleted + doc.make_tombstone() + self.put_doc(doc) + + def create_index(self, index_name, *index_expressions): + if index_name in self._indexes: + if self._indexes[index_name]._definition == list( + index_expressions): + return + raise errors.IndexNameTakenError + index = InMemoryIndex(index_name, list(index_expressions)) + for doc_id, (doc_rev, doc) in self._docs.iteritems(): + if doc is not None: + index.add_json(doc_id, doc) + self._indexes[index_name] = index + + def delete_index(self, index_name): + del self._indexes[index_name] + + def list_indexes(self): + definitions = [] + for idx in self._indexes.itervalues(): + definitions.append((idx._name, idx._definition)) + return definitions + + def get_from_index(self, index_name, *key_values): + try: + index = self._indexes[index_name] + except KeyError: + raise errors.IndexDoesNotExist + doc_ids = index.lookup(key_values) + result = [] + for doc_id in doc_ids: + result.append(self._get_doc(doc_id, check_for_conflicts=True)) + return result + + def get_range_from_index(self, index_name, start_value=None, + end_value=None): + """Return all documents with key values in the specified range.""" + try: + index = self._indexes[index_name] + except KeyError: + raise errors.IndexDoesNotExist + if isinstance(start_value, basestring): + start_value = (start_value,) + if isinstance(end_value, basestring): + end_value = (end_value,) + doc_ids = index.lookup_range(start_value, end_value) + result = [] + for doc_id in doc_ids: + result.append(self._get_doc(doc_id, check_for_conflicts=True)) + return result + + def get_index_keys(self, index_name): + try: + index = self._indexes[index_name] + except KeyError: + raise errors.IndexDoesNotExist + keys = index.keys() + # XXX inefficiency warning + return list(set([tuple(key.split('\x01')) for key in keys])) + + def whats_changed(self, old_generation=0): + changes = [] + relevant_tail = self._transaction_log[old_generation:] + # We don't use len(self._transaction_log) because _transaction_log may + # get mutated by a concurrent operation. + cur_generation = old_generation + len(relevant_tail) + last_trans_id = '' + if relevant_tail: + last_trans_id = relevant_tail[-1][1] + elif self._transaction_log: + last_trans_id = self._transaction_log[-1][1] + seen = set() + generation = cur_generation + for doc_id, trans_id in reversed(relevant_tail): + if doc_id not in seen: + changes.append((doc_id, generation, trans_id)) + seen.add(doc_id) + generation -= 1 + changes.reverse() + return (cur_generation, last_trans_id, changes) + + def _force_doc_sync_conflict(self, doc): + my_doc = self._get_doc(doc.doc_id) + self._prune_conflicts(doc, vectorclock.VectorClockRev(doc.rev)) + self._conflicts.setdefault(doc.doc_id, []).append( + (my_doc.rev, my_doc.get_json())) + doc.has_conflicts = True + self._put_and_update_indexes(my_doc, doc) + + +class InMemoryIndex(object): + """Interface for managing an Index.""" + + def __init__(self, index_name, index_definition): + self._name = index_name + self._definition = index_definition + self._values = {} + parser = query_parser.Parser() + self._getters = parser.parse_all(self._definition) + + def evaluate_json(self, doc): + """Determine the 'key' after applying this index to the doc.""" + raw = json.loads(doc) + return self.evaluate(raw) + + def evaluate(self, obj): + """Evaluate a dict object, applying this definition.""" + all_rows = [[]] + for getter in self._getters: + new_rows = [] + keys = getter.get(obj) + if not keys: + return [] + for key in keys: + new_rows.extend([row + [key] for row in all_rows]) + all_rows = new_rows + all_rows = ['\x01'.join(row) for row in all_rows] + return all_rows + + def add_json(self, doc_id, doc): + """Add this json doc to the index.""" + keys = self.evaluate_json(doc) + if not keys: + return + for key in keys: + self._values.setdefault(key, []).append(doc_id) + + def remove_json(self, doc_id, doc): + """Remove this json doc from the index.""" + keys = self.evaluate_json(doc) + if keys: + for key in keys: + doc_ids = self._values[key] + doc_ids.remove(doc_id) + if not doc_ids: + del self._values[key] + + def _find_non_wildcards(self, values): + """Check if this should be a wildcard match. + + Further, this will raise an exception if the syntax is improperly + defined. + + :return: The offset of the last value we need to match against. + """ + if len(values) != len(self._definition): + raise errors.InvalidValueForIndex() + is_wildcard = False + last = 0 + for idx, val in enumerate(values): + if val.endswith('*'): + if val != '*': + # We have an 'x*' style wildcard + if is_wildcard: + # We were already in wildcard mode, so this is invalid + raise errors.InvalidGlobbing + last = idx + 1 + is_wildcard = True + else: + if is_wildcard: + # We were in wildcard mode, we can't follow that with + # non-wildcard + raise errors.InvalidGlobbing + last = idx + 1 + if not is_wildcard: + return -1 + return last + + def lookup(self, values): + """Find docs that match the values.""" + last = self._find_non_wildcards(values) + if last == -1: + return self._lookup_exact(values) + else: + return self._lookup_prefix(values[:last]) + + def lookup_range(self, start_values, end_values): + """Find docs within the range.""" + # TODO: Wildly inefficient, which is unlikely to be a problem for the + # inmemory implementation. + if start_values: + self._find_non_wildcards(start_values) + start_values = get_prefix(start_values) + if end_values: + if self._find_non_wildcards(end_values) == -1: + exact = True + else: + exact = False + end_values = get_prefix(end_values) + found = [] + for key, doc_ids in sorted(self._values.iteritems()): + if start_values and start_values > key: + continue + if end_values and end_values < key: + if exact: + break + else: + if not key.startswith(end_values): + break + found.extend(doc_ids) + return found + + def keys(self): + """Find the indexed keys.""" + return self._values.keys() + + def _lookup_prefix(self, value): + """Find docs that match the prefix string in values.""" + # TODO: We need a different data structure to make prefix style fast, + # some sort of sorted list would work, but a plain dict doesn't. + key_prefix = get_prefix(value) + all_doc_ids = [] + for key, doc_ids in sorted(self._values.iteritems()): + if key.startswith(key_prefix): + all_doc_ids.extend(doc_ids) + return all_doc_ids + + def _lookup_exact(self, value): + """Find docs that match exactly.""" + key = '\x01'.join(value) + if key in self._values: + return self._values[key] + return () + + +class InMemorySyncTarget(CommonSyncTarget): + + def get_sync_info(self, source_replica_uid): + source_gen, source_trans_id = self._db._get_replica_gen_and_trans_id( + source_replica_uid) + my_gen, my_trans_id = self._db._get_generation_info() + return ( + self._db._replica_uid, my_gen, my_trans_id, source_gen, + source_trans_id) + + def record_sync_info(self, source_replica_uid, source_replica_generation, + source_transaction_id): + if self._trace_hook: + self._trace_hook('record_sync_info') + self._db._set_replica_gen_and_trans_id( + source_replica_uid, source_replica_generation, + source_transaction_id) |