move src/gdatastore to top level (distutils-extra convention)

3 files changed, 868 insertions, 0 deletions

diff --git a/gdatastore/__init__.py b/gdatastore/__init__.py
new file mode 100644
index 0000000..e69de29
--- /dev/null
+++ b/gdatastore/__init__.py
diff --git a/gdatastore/datastore.py b/gdatastore/datastore.py
new file mode 100644
index 0000000..1cb8555
--- /dev/null
+++ b/gdatastore/datastore.py
@@ -0,0 +1,473 @@
+#
+# Author: Sascha Silbe <sascha-pgp@silbe.org>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3
+# as published by the Free Software Foundation.
+#
+# This program 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+Gdatastore D-Bus service API
+"""
+
+import hashlib
+import logging
+import os
+import shutil
+from subprocess import Popen, PIPE
+import tempfile
+import time
+import uuid
+
+import dbus
+import dbus.service
+import gconf
+
+from gdatastore.index import Index
+
+
+DBUS_SERVICE_NATIVE_V1 = 'org.silbe.GDataStore'
+DBUS_INTERFACE_NATIVE_V1 = 'org.silbe.GDataStore1'
+DBUS_PATH_NATIVE_V1 = '/org/silbe/GDataStore1'
+
+DBUS_SERVICE_SUGAR_V2 = 'org.laptop.sugar.DataStore'
+DBUS_INTERFACE_SUGAR_V2 = 'org.laptop.sugar.DataStore'
+DBUS_PATH_SUGAR_V2 = '/org/laptop/sugar/DataStore'
+
+DBUS_SERVICE_SUGAR_V3 = 'org.laptop.sugar.DataStore'
+DBUS_INTERFACE_SUGAR_V3 = 'org.laptop.sugar.DataStore2'
+DBUS_PATH_SUGAR_V3 = '/org/laptop/sugar/DataStore2'
+
+
+class DataStoreError(Exception):
+    pass
+
+
+class GitError(DataStoreError):
+    def __init__(self, returncode, stderr):
+        self.returncode = returncode
+        self.stderr = unicode(stderr)
+        Exception.__init__(self)
+
+    def __unicode__(self):
+        return u'Git returned with exit code #%d: %s' % (self.returncode,
+                                                         self.stderr)
+
+    def __str__(self):
+        return self.__unicode__()
+
+
+class DBusApiSugarV2(dbus.service.Object):
+    """Compatibility layer for the Sugar 0.84+ data store D-Bus API
+    """
+
+    def __init__(self, internal_api):
+        self._internal_api = internal_api
+        bus_name = dbus.service.BusName(DBUS_SERVICE_SUGAR_V2,
+                                        bus=dbus.SessionBus(),
+                                        replace_existing=False,
+                                        allow_replacement=False)
+        dbus.service.Object.__init__(self, bus_name, DBUS_PATH_SUGAR_V2)
+
+    @dbus.service.method(DBUS_INTERFACE_SUGAR_V2,
+                         in_signature='a{sv}sb', out_signature='s',
+                         async_callbacks=('async_cb', 'async_err_cb'),
+                         byte_arrays=True)
+    def create(self, props, file_path, transfer_ownership,
+               async_cb, async_err_cb):
+        def success_cb(tree_id, child_id):
+            self.Created(tree_id)
+            async_cb(tree_id)
+
+        self._internal_api.save(tree_id='', parent_id='', metadata=props,
+                                path=file_path,
+                                delete_after=transfer_ownership,
+                                async_cb=success_cb,
+                                async_err_cb=async_err_cb)
+
+    @dbus.service.signal(DBUS_INTERFACE_SUGAR_V2, signature='s')
+    def Created(self, uid):
+        # pylint: disable-msg=C0103
+        pass
+
+    @dbus.service.method(DBUS_INTERFACE_SUGAR_V2,
+                         in_signature='sa{sv}sb', out_signature='',
+                         async_callbacks=('async_cb', 'async_err_cb'),
+                         byte_arrays=True)
+    def update(self, uid, props, file_path, transfer_ownership,
+               async_cb, async_err_cb):
+        def success_cb(tree_id, child_id):
+            self.Updated(tree_id)
+            async_cb()
+
+        latest_versions = self._get_latest(uid)
+        if not latest_versions:
+            raise ValueError('Trying to update non-existant entry %s - wanted'
+                ' to use create()?' % (uid, ))
+
+        parent = latest_versions[0]
+        object_id = parent['tree_id'], parent['version_id']
+        if self._compare_checksums(parent, file_path):
+            self._internal_api.change_metadata(object_id, props)
+            return success_cb(uid, None)
+
+        self._internal_api.save(tree_id=uid,
+            parent_id=parent['version_id'], metadata=props,
+            path=file_path, delete_after=transfer_ownership,
+            async_cb=success_cb, async_err_cb=async_err_cb)
+
+    @dbus.service.signal(DBUS_INTERFACE_SUGAR_V2, signature='s')
+    def Updated(self, uid):
+        # pylint: disable-msg=C0103
+        pass
+
+    @dbus.service.method(DBUS_INTERFACE_SUGAR_V2,
+                         in_signature='a{sv}as', out_signature='aa{sv}u')
+    def find(self, query, properties):
+        if 'uid' in properties:
+            properties.append('tree_id')
+            properties.remove('uid')
+
+        options = {'metadata': properties}
+        for name in ['offset', 'limit', 'order_by']:
+            if name in query:
+                options[name] = query.pop(name)
+
+        if 'uid' in query:
+            query['tree_id'] = query.pop('uid')
+
+        results, count = self._internal_api.find(query, options,
+            query.pop('query', None))
+
+        if not properties or 'tree_id' in properties:
+            for entry in results:
+                entry['uid'] = entry.pop('tree_id')
+
+        return results, count
+
+    @dbus.service.method(DBUS_INTERFACE_SUGAR_V2,
+                         in_signature='s', out_signature='s',
+                         sender_keyword='sender')
+    def get_filename(self, uid, sender=None):
+        latest_versions = self._get_latest(uid)
+        if not latest_versions:
+            raise ValueError('Entry %s does not exist' % (uid, ))
+
+        object_id = (uid, latest_versions[0]['version_id'])
+        return self._internal_api.get_data_path(object_id, sender=sender)
+
+    @dbus.service.method(DBUS_INTERFACE_SUGAR_V2,
+                         in_signature='s', out_signature='a{sv}')
+    def get_properties(self, uid):
+        latest_versions = self._get_latest(uid)
+        if not latest_versions:
+            raise ValueError('Entry %s does not exist' % (uid, ))
+
+        latest_versions[0]['uid'] = latest_versions[0].pop('tree_id')
+        del latest_versions[0]['version_id']
+        return latest_versions[0]
+
+    @dbus.service.method(DBUS_INTERFACE_SUGAR_V2,
+                         in_signature='sa{sv}', out_signature='as')
+    def get_uniquevaluesfor(self, propertyname, query=None):
+        return self._internal_api.find_unique_values(query, propertyname)
+
+    @dbus.service.method(DBUS_INTERFACE_SUGAR_V2,
+                         in_signature='s', out_signature='')
+    def delete(self, uid):
+        latest_versions = self._get_latest(uid)
+        if not latest_versions:
+            raise ValueError('Entry %s does not exist' % (uid, ))
+
+        self._internal_api.delete((uid, latest_versions[0]['version_id']))
+        self.Deleted(uid)
+
+    @dbus.service.signal(DBUS_INTERFACE_SUGAR_V2, signature='s')
+    def Deleted(self, uid):
+        # pylint: disable-msg=C0103
+        pass
+
+    @dbus.service.method(DBUS_INTERFACE_SUGAR_V2,
+                         in_signature='', out_signature='aa{sv}')
+    def mounts(self):
+        return [{'id': 1}]
+
+    @dbus.service.signal(DBUS_INTERFACE_SUGAR_V2, signature='a{sv}')
+    def Mounted(self, descriptior):
+        # pylint: disable-msg=C0103
+        pass
+
+    @dbus.service.signal(DBUS_INTERFACE_SUGAR_V2, signature='a{sv}')
+    def Unmounted(self, descriptor):
+        # pylint: disable-msg=C0103
+        pass
+
+    def _get_latest(self, uid):
+        return self._internal_api.find({'tree_id': uid},
+            {'limit': 1, 'order_by': ['+timestamp']})[0]
+
+    def _compare_checksums(self, parent, child_data_path):
+        parent_object_id = (parent['tree_id'], parent['version_id'])
+        parent_data_path = self._internal_api.get_data_path(parent_object_id)
+        if bool(child_data_path) ^ bool(parent_data_path):
+            return False
+        elif not child_data_path:
+            return True
+
+        return False
+        parent_checksum = self._internal_api.get_data_checksum(
+            parent_object_id)
+        child_checksum = calculate_checksum(child_data_path)
+        return parent_checksum == child_checksum
+
+
+class InternalApi(object):
+    def __init__(self, base_dir):
+        self._base_dir = base_dir
+        self._checkouts_dir = os.path.join(base_dir, 'checkouts')
+        if not os.path.exists(self._checkouts_dir):
+            os.makedirs(self._checkouts_dir)
+        self._git_dir = os.path.join(base_dir, 'git')
+        self._git_env = {}
+        gconf_client = gconf.client_get_default()
+        self._max_versions = gconf_client.get_int(
+            '/desktop/sugar/datastore/max_versions')
+        logging.debug('max_versions=%r', self._max_versions)
+        self._index = Index(os.path.join(self._base_dir, 'index'))
+        self._migrate()
+        self._metadata = {}
+
+    def change_metadata(self, object_id, metadata):
+        logging.debug('change_metadata(%r, %r)', object_id, metadata)
+        metadata['tree_id'], metadata['version_id'] = object_id
+        if 'creation_time' not in metadata:
+            old_metadata = self._metadata[object_id]
+            metadata['creation_time'] = old_metadata['creation_time']
+
+        self._index.store(object_id, metadata)
+        self._metadata[object_id] = metadata
+
+    def delete(self, object_id):
+        logging.debug('delete(%r)', object_id)
+        self._index.delete(object_id)
+        del self._metadata[object_id]
+        self._git_call('update-ref', ['-d', _format_ref(*object_id)])
+
+    def get_data_path(self, (tree_id, version_id), sender=None):
+        logging.debug('get_data_path((%r, %r), %r)', tree_id, version_id,
+                      sender)
+        ref_name = _format_ref(tree_id, version_id)
+        top_level_entries = self._git_call('ls-tree',
+                                           [ref_name]).splitlines()
+        if len(top_level_entries) == 1 and \
+           top_level_entries[0].endswith('\tdata'):
+            blob_hash = top_level_entries[0].split('\t')[0].split(' ')[2]
+            return self._checkout_file(blob_hash)
+
+        return self._checkout_dir(ref_name)
+
+    def find(self, query_dict, options, query_string=None):
+        logging.debug('find(%r, %r, %r)', query_dict, options, query_string)
+        entries, total_count = self._index.find(query_dict, query_string,
+                                                options)
+        #logging.debug('object_ids=%r', object_ids)
+        property_names = options.pop('metadata', None)
+        for entry in entries:
+            for name in entry.keys():
+                if property_names and name not in property_names:
+                    del entry[name]
+                elif isinstance(entry[name], str):
+                    entry[name] = dbus.ByteArray(entry[name])
+
+        return entries, total_count
+
+    def find_unique_values(self, query, name):
+        logging.debug('find_unique_values(%r, %r)', query, name)
+        return ['org.sugarlabs.DataStoreTest1', 'org.sugarlabs.DataStoreTest2']
+
+    def save(self, tree_id, parent_id, metadata, path, delete_after, async_cb,
+             async_err_cb):
+        logging.debug('save(%r, %r, %r, %r, %r)', tree_id, parent_id,
+                      metadata, path, delete_after)
+
+        if path:
+            path = os.path.realpath(path)
+            if not os.access(path, os.R_OK):
+                raise ValueError('Invalid path given.')
+
+            if delete_after and not os.access(os.path.dirname(path), os.W_OK):
+                raise ValueError('Deletion requested for read-only directory')
+
+        if (not tree_id) and parent_id:
+            raise ValueError('tree_id is empty but parent_id is not')
+
+        if tree_id and not parent_id:
+            if self.find({'tree_id': tree_id}, {'limit': 1})[1]:
+                raise ValueError('No parent_id given but tree_id already '
+                                 'exists')
+
+        elif parent_id:
+            if not self._index.contains((tree_id, parent_id)):
+                raise ValueError('Given parent does not exist')
+
+        if not tree_id:
+            tree_id = self._gen_uuid()
+
+        child_id = metadata.get('version_id')
+        if not child_id:
+            child_id = self._gen_uuid()
+        elif not tree_id:
+            raise ValueError('No tree_id given but metadata contains'
+                             ' version_id')
+        elif self._index.contains((tree_id, child_id)):
+            raise ValueError('There is an existing entry with the same tree_id'
+                             ' and version_id')
+
+        if 'timestamp' not in metadata:
+            metadata['timestamp'] = time.time()
+
+        if 'creation_time' not in metadata:
+            metadata['creation_time'] = metadata['timestamp']
+
+        if os.path.isfile(path):
+            metadata['filesize'] = str(os.stat(path).st_size)
+        elif not path:
+            metadata['filesize'] = '0'
+
+        tree_id = str(tree_id)
+        parent_id = str(parent_id)
+        child_id = str(child_id)
+
+        metadata['tree_id'] = tree_id
+        metadata['version_id'] = child_id
+
+        # TODO: check metadata for validity first (index?)
+        self._store_entry(tree_id, child_id, parent_id, path, metadata)
+        self._metadata[(tree_id, child_id)] = metadata
+        self._index.store((tree_id, child_id), metadata)
+        async_cb(tree_id, child_id)
+
+    def stop(self):
+        logging.debug('stop()')
+        self._index.close()
+
+    def _add_to_index(self, index_path, path):
+        if os.path.isdir(path):
+            self._git_call('add', ['-A'], work_dir=path, index_path=index_path)
+        elif os.path.isfile(path):
+            object_hash = self._git_call('hash-object', ['-w', path]).strip()
+            mode = os.stat(path).st_mode
+            self._git_call('update-index',
+                           ['--add',
+                            '--cacheinfo', oct(mode), object_hash, 'data'],
+                           index_path=index_path)
+        else:
+            raise DataStoreError('Refusing to store special object %r' % (path, ))
+
+    def _check_max_versions(self, tree_id):
+        if not self._max_versions:
+            return
+
+        options = {'all_versions': True, 'offset': self._max_versions,
+                   'metadata': ['tree_id', 'version_id', 'timestamp'],
+                   'order_by': ['+timestamp']}
+        old_versions = self.find({'tree_id': tree_id}, options)[0]
+        logging.info('Deleting old versions: %r', old_versions)
+        for entry in old_versions:
+            self.delete((entry['tree_id'], entry['version_id']))
+
+    def _checkout_file(self, blob_hash):
+        fd, file_name = tempfile.mkstemp(dir=self._checkouts_dir)
+        try:
+            self._git_call('cat-file', ['blob', blob_hash], stdout_fd=fd)
+        finally:
+            os.close(fd)
+        return file_name
+
+    def _checkout_dir(self, ref_name):
+        # FIXME
+        return ''
+
+    def _create_repo(self):
+        os.makedirs(self._git_dir)
+        self._git_call('init', ['-q', '--bare'])
+
+    def _find_git_parent(self, tree_id, parent_id):
+        if not parent_id:
+            return None
+
+        return self._git_call('rev-parse',
+                              [_format_ref(tree_id, parent_id)]).strip()
+
+    def _format_commit_message(self, metadata):
+        return repr(metadata)
+
+    def _gen_uuid(self):
+        return str(uuid.uuid4())
+
+    def _git_call(self, command, args=None, input=None, input_fd=None,
+                  stdout_fd=None, work_dir=None, index_path=None):
+        env = dict(self._git_env)
+        if work_dir:
+            env['GIT_WORK_TREE'] = work_dir
+        if index_path:
+            env['GIT_INDEX_FILE'] = index_path
+        logging.debug('calling git %s, env=%r', ['git', command] + (args or []), env)
+        pipe = Popen(['git', command] + (args or []), stdin=input_fd or PIPE,
+                     stdout=stdout_fd or PIPE, stderr=PIPE, close_fds=True,
+                     cwd=self._git_dir, env=env)
+        stdout, stderr = pipe.communicate(input)
+        if pipe.returncode:
+            raise GitError(pipe.returncode, stderr)
+        return stdout
+
+    def _migrate(self):
+        if not os.path.exists(self._git_dir):
+            return self._create_repo()
+
+    def _store_entry(self, tree_id, version_id, parent_id, path, metadata):
+        parent_hash = self._find_git_parent(tree_id, parent_id)
+        commit_message = self._format_commit_message(metadata)
+        tree_hash = self._write_tree(path)
+        commit_options = [tree_hash]
+        if parent_hash:
+            commit_options += ['-p', parent_hash]
+        commit_hash = self._git_call('commit-tree', commit_options,
+                                     input=commit_message).strip()
+        self._git_call('update-ref', [_format_ref(tree_id, version_id),
+                                      commit_hash])
+
+    def _write_tree(self, path):
+        if not path:
+            return self._git_call('hash-object',
+                                  ['-w', '-t', 'tree', '--stdin'],
+                                  input='').strip()
+
+        index_dir = tempfile.mkdtemp(prefix='gdatastore-')
+        index_path = os.path.join(index_dir, 'index')
+        try:
+            self._add_to_index(index_path, path)
+            return self._git_call('write-tree', index_path=index_path).strip()
+        finally:
+            shutil.rmtree(index_dir)
+
+
+def calculate_checksum(path):
+    checksum = hashlib.sha1()
+    f = file(path)
+    while True:
+        chunk = f.read(65536)
+        if not chunk:
+            return checksum.hexdigest()
+
+        checksum.update(chunk)
+
+
+def _format_ref(tree_id, version_id):
+    return 'refs/gdatastore/%s/%s' % (tree_id, version_id)
diff --git a/gdatastore/index.py b/gdatastore/index.py
new file mode 100644
index 0000000..c93f5b3
--- /dev/null
+++ b/gdatastore/index.py
@@ -0,0 +1,395 @@
+#
+# Author: Sascha Silbe <sascha-pgp@silbe.org>
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3
+# as published by the Free Software Foundation.
+#
+# This program 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 General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program. If not, see <http://www.gnu.org/licenses/>.
+"""
+Gdatastore metadata index interface
+"""
+
+import logging
+import os
+import sys
+
+import xapian
+from xapian import Document, Enquire, Query, WritableDatabase
+
+
+_CURRENT_VERSION = 1
+_STANDARD_TERMS = {
+    'activity': {'prefix': 'Xactname', 'type': str},
+    'activity_id': {'prefix': 'Xactid', 'type': str},
+    'description': {'prefix': 'Xdesc', 'type': unicode},
+    'keep': {'prefix': 'Xkeep', 'type': str},
+    'mime_type': {'prefix': 'T', 'type': str},
+    'tags': {'prefix': 'K', 'type': unicode},
+    'title': {'prefix': 'S', 'type': unicode},
+    'tree_id': {'prefix': 'Xtree', 'type': str},
+    'version_id': {'prefix': 'Xversion', 'type': str},
+}
+_VALUE_TREE_ID = 0
+_VALUE_VERSION_ID = 1
+_VALUE_MTIME = 2
+_VALUE_SIZE = 3
+_VALUE_CTIME = 4
+_STANDARD_VALUES = {
+    'creation_time': {'number': _VALUE_CTIME, 'type': float},
+    'filesize': {'number': _VALUE_SIZE, 'type': int},
+    'timestamp': {'number': _VALUE_MTIME, 'type': float},
+    'tree_id': {'number': _VALUE_TREE_ID, 'type': str},
+    'version_id': {'number': _VALUE_VERSION_ID, 'type': str},
+}
+_IGNORE_PROPERTIES = ['preview']
+_PREFIX_FULL_VALUE = 'Xf'
+_PREFIX_OBJECT_ID = 'Q'
+_LIMIT_MAX = 2 ** 31 - 1
+_DOCID_REVERSE_MAP = {True: Enquire.DESCENDING, False: Enquire.ASCENDING}
+
+
+class DSIndexError(Exception):
+    pass
+
+
+class TermGenerator(xapian.TermGenerator):
+
+    def __init__(self):
+        self._document = None
+        xapian.TermGenerator.__init__(self)
+
+    def index_document(self, document, properties):
+        for name, info in _STANDARD_VALUES.items():
+            if name not in properties:
+                continue
+
+            document.add_value(info['number'],
+                _serialise_value(info, properties[name]))
+
+        self._document = document
+        self.set_document(document)
+
+        properties = dict(properties)
+        self._index_known(properties)
+        self._index_unknown(properties)
+
+    def _index_known(self, properties):
+        """Index standard properties and remove them from the input."""
+        for name, info in _STANDARD_TERMS.items():
+            if name not in properties:
+                continue
+
+            self._index_property(properties.pop(name), info['prefix'])
+
+    def _index_unknown(self, properties):
+        """
+        Index all given properties.
+
+        Expects not to get passed any standard term-stored property.
+        """
+        for name, value in properties.items():
+            if name in _IGNORE_PROPERTIES or name in _STANDARD_VALUES:
+                continue
+
+            if isinstance(value, unicode):
+                value = value.encode('utf-8')
+            elif not isinstance(value, str):
+                value = str(value)
+
+            self._index_property(_prefix_for_unknown(name), value)
+
+    def _index_property(self, value, prefix):
+        # We need to add the full value (i.e. not split into words), too, so
+        # we can enumerate unique values. It also simplifies setting up
+        # dictionary-based queries.
+        self._document.add_term(_PREFIX_FULL_VALUE + prefix + value)
+        self.index_text(value, 1, prefix)
+        self.increase_termpos()
+
+
+class QueryParser(xapian.QueryParser):
+    """
+    QueryParser that understands dictionaries and Xapian query strings.
+
+    The dictionary may contain property names as keys and basic types
+    (exact match), 2-tuples (range, only valid for value-stored
+    standard properties) and lists (multiple exact matches joined with
+    OR) as values.
+    An empty dictionary matches everything. Queries from different keys
+    (i.e. different property names) are joined with AND.
+
+    Full text search (Xapian query string) is only supported for standard
+    properties.
+    """
+
+    _FLAGS = (xapian.QueryParser.FLAG_PHRASE |
+              xapian.QueryParser.FLAG_BOOLEAN |
+              xapian.QueryParser.FLAG_LOVEHATE |
+              xapian.QueryParser.FLAG_WILDCARD)
+
+    def __init__(self):
+        xapian.QueryParser.__init__(self)
+        for name, info in _STANDARD_TERMS.items():
+            self.add_prefix(name, info['prefix'])
+            self.add_prefix('', info['prefix'])
+
+    def _parse_query_term(self, prefix, value):
+        if isinstance(value, list):
+            subqueries = [self._parse_query_term(prefix, word)
+                          for word in value]
+            return Query(Query.OP_OR, subqueries)
+
+        return Query(_PREFIX_FULL_VALUE + prefix + str(value))
+
+    def _parse_query_value_range(self, info, value):
+        if len(value) != 2:
+            raise TypeError('Only tuples of size 2 have a defined meaning.'
+                            ' Did you mean to pass a list instead?')
+
+        start, end = value
+        return Query(Query.OP_VALUE_RANGE, info['number'],
+                     _serialise_value(info, start),
+                     _serialise_value(info, end))
+
+    def _parse_query_value(self, info, value):
+        if isinstance(value, list):
+            subqueries = [self._parse_query_value(info, word)
+                          for word in value]
+            return Query(Query.OP_OR, subqueries)
+
+        elif isinstance(value, tuple):
+            return self._parse_query_value_range(info, value)
+
+        elif isinstance(value, dict):
+            # compatibility option for timestamp: {'start': 0, 'end': 1}
+            start = value.get('start', 0)
+            end = value.get('end', sys.maxint)
+            return self._parse_query_value_range(info, (start, end))
+
+        else:
+            return self._parse_query_value_range(info, (value, value))
+
+    def _parse_query_xapian(self, query_str):
+        return xapian.QueryParser.parse_query(self, query_str,
+                                              QueryParser._FLAGS, '')
+
+    def parse_datastore_query(self, query_dict, query_string):
+        logging.debug('query_dict=%r, query_string=%r', query_dict,
+                      query_string)
+        queries = []
+        query_dict = dict(query_dict or {})
+
+        if query_string is not None:
+            queries.append(self._parse_query_xapian(str(query_string)))
+
+        for name, value in query_dict.items():
+            if name in _STANDARD_TERMS:
+                prefix = _STANDARD_TERMS[name]['prefix']
+                query = self._parse_query_term(prefix, value)
+            elif name in _STANDARD_VALUES:
+                info = _STANDARD_VALUES[name]
+                query = self._parse_query_value(info, value)
+            else:
+                logging.warning('Unknown term: %r=%r', name, value)
+                continue
+
+            queries.append(query)
+
+        if not queries:
+            queries.append(Query(''))
+
+        logging.debug('queries: %r', [str(query) for query in queries])
+        return Query(Query.OP_AND, queries)
+
+
+class Index(object):
+
+    def __init__(self, base_dir):
+        self._base_dir = base_dir
+        self._database = None
+
+        if not os.path.exists(self._base_dir):
+            os.makedirs(self._base_dir)
+            self._create_database()
+
+        self._migrate()
+        self._query_parser = QueryParser()
+        self._query_parser.set_database(self._database)
+
+    def close(self):
+        """Close index database if it is open."""
+        if not self._database:
+            return
+
+        self._database.close()
+        self._database = None
+
+    def contains(self, object_id):
+        postings = self._database.postlist(_object_id_term(object_id))
+        try:
+            _ = postings.next()
+        except StopIteration:
+            return False
+        return True
+
+    def delete(self, object_id):
+        object_id_term = _object_id_term(object_id)
+        if __debug__:
+            enquire = Enquire(self._database)
+            enquire.set_query(Query(object_id_term))
+            documents = [hit.document for hit in enquire.get_mset(0, 2, 2)]
+            assert len(documents) == 1
+
+        self._database.delete_document(object_id_term)
+
+    def find(self, query_dict, query_string, options):
+        offset = options.pop('offset', 0)
+        limit = options.pop('limit', _LIMIT_MAX)
+        order_by = options.pop('order_by', ['+timestamp'])[0]
+        all_versions = options.pop('all_versions', False)
+        check_at_least = options.pop('check_at_least', offset + limit + 1)
+
+        enquire = Enquire(self._database)
+        query = self._query_parser.parse_datastore_query(query_dict,
+                                                         query_string)
+        enquire.set_query(query)
+
+        sort_reverse = {'+': True, '-': False}[order_by[0]]
+        try:
+            sort_value_nr = _STANDARD_VALUES[order_by[1:]]['number']
+        except KeyError:
+            logging.warning('Trying to order by unknown property: %r',
+                            order_by[1:])
+            sort_value_nr = _VALUE_MTIME
+
+        enquire.set_sort_by_value(sort_value_nr, reverse=sort_reverse)
+        enquire.set_docid_order(_DOCID_REVERSE_MAP[sort_reverse])
+
+        if not all_versions:
+            enquire.set_collapse_key(_VALUE_TREE_ID)
+
+        if not all_versions and order_by != '+timestamp':
+            # Xapian doesn't support using a different sort order while
+            # collapsing (which needs to be timestamp in our case), so
+            # we need to query everything and sort+limit ourselves.
+            enquire.set_sort_by_value(_VALUE_MTIME, True)
+            enquire.set_docid_order(enquire.ASCENDING)
+            query_result = enquire.get_mset(0, _LIMIT_MAX, _LIMIT_MAX)
+        else:
+            logging.debug('Offset/limit using Xapian: %d %d %d', offset, limit, check_at_least)
+            query_result = enquire.get_mset(offset, limit, check_at_least)
+
+        total_count = query_result.get_matches_lower_bound()
+        documents = [hit.document for hit in query_result]
+
+        if (not all_versions) and (order_by != '+timestamp'):
+            _sort_documents(documents, sort_value_nr, sort_reverse)
+            del documents[offset + limit:]
+
+        #object_ids = [(document.get_value(_VALUE_TREE_ID),
+        #               document.get_value(_VALUE_VERSION_ID))
+        #              for document in documents]
+        entries = [deserialise_metadata(document.get_data())
+                   for document in documents]
+
+        return entries, total_count
+
+    def store(self, object_id, properties):
+        logging.debug('store(%r, %r)', object_id, properties)
+        assert (properties['tree_id'], properties['version_id']) == object_id
+        id_term = _object_id_term(object_id)
+        document = Document()
+        logging.debug('serialised=%r', serialiase_metadata(properties))
+        document.set_data(serialiase_metadata(properties))
+        document.add_term(id_term)
+        term_generator = TermGenerator()
+        term_generator.index_document(document, properties)
+        assert (document.get_value(_VALUE_TREE_ID), document.get_value(_VALUE_VERSION_ID)) == object_id
+        self._database.replace_document(id_term, document)
+
+    def _create_database(self):
+        database = WritableDatabase(self._base_dir, xapian.DB_CREATE_OR_OPEN)
+        database.set_metadata('gdatastore_version', str(_CURRENT_VERSION))
+        database.close()
+
+    def _migrate(self):
+        self._database = WritableDatabase(self._base_dir,
+                                          xapian.DB_CREATE_OR_OPEN)
+        version = int(self._database.get_metadata('gdatastore_version'))
+
+        if version > _CURRENT_VERSION:
+            raise DSIndexError('Unsupported index version: %d > %d' %
+                             (version, _CURRENT_VERSION))
+
+
+def deserialise_metadata(serialised):
+    """Deserialise a string generated by serialise_metadata().
+
+    Do NOT pass any value that might have been modified since it was generated
+    by serialiase_metadata().
+    """
+    return eval(serialised)
+
+
+def serialiase_metadata(metadata):
+    return repr(_to_native(metadata))
+
+
+def _object_id_term(object_id):
+    return _PREFIX_FULL_VALUE + _PREFIX_OBJECT_ID + '%s-%s' % object_id
+
+
+def _prefix_for_unknown(name):
+    return 'Xu%d:%s' % (len(name), unicode(name).encode('utf-8'))
+
+
+def _serialise_value(info, value):
+    if info['type'] in (float, int, long):
+        return xapian.sortable_serialise(info['type'](value))
+    elif info['type'] == unicode:
+        return unicode(value).encode('utf-8')
+
+    return str(info['type'](value))
+
+
+def _sort_documents(documents, sort_value_nr, sort_reverse):
+    def _cmp(document_a, document_b):
+        value_a = document_a.get_value(sort_value_nr)
+        value_b = document_b.get_value(sort_value_nr)
+        if value_a < value_b:
+            return -1
+        elif value_a > value_b:
+            return 1
+
+        docid_a = document_a.get_docid()
+        docid_b = document_b.get_docid()
+        if docid_a < docid_b:
+            return -1
+        elif docid_a > docid_b:
+            return 1
+        return 0
+
+    documents.sort(cmp=_cmp, reverse=sort_reverse)
+
+
+def _to_native(value):
+    if isinstance(value, list):
+        return [_to_native(e) for e in value]
+    elif isinstance(value, dict):
+        return dict([(_to_native(k), _to_native(v)) for k, v in value.items()])
+    elif isinstance(value, unicode):
+        return unicode(value)
+    elif isinstance(value, str):
+        return str(value)
+    elif isinstance(value, int):
+        return int(value)
+    elif isinstance(value, float):
+        return float(value)
+    return value