[refactor] merge refactor from drebs

18 files changed, 1330 insertions, 81 deletions

diff --git a/client/src/leap/soledad/client/__init__.py b/client/src/leap/soledad/client/__init__.py
index 3a114021..bcad78db 100644
--- a/client/src/leap/soledad/client/__init__.py
+++ b/client/src/leap/soledad/client/__init__.py
@@ -17,12 +17,14 @@
 """
 Soledad - Synchronization Of Locally Encrypted Data Among Devices.
 """
-from leap.soledad.client.api import Soledad
 from leap.soledad.common import soledad_assert
 
+from .api import Soledad
+from ._document import Document, AttachmentStates
 from ._version import get_versions
 
 __version__ = get_versions()['version']
 del get_versions
 
-__all__ = ['soledad_assert', 'Soledad', '__version__']
+__all__ = ['soledad_assert', 'Soledad', 'Document', 'AttachmentStates',
+           '__version__']
diff --git a/client/src/leap/soledad/client/_crypto.py b/client/src/leap/soledad/client/_crypto.py
index 7a1d508e..e66cc600 100644
--- a/client/src/leap/soledad/client/_crypto.py
+++ b/client/src/leap/soledad/client/_crypto.py
@@ -135,7 +135,7 @@ class SoledadCrypto(object):
         and wrapping the result as a simple JSON string with a "raw" key.
 
         :param doc: the document to be encrypted.
-        :type doc: SoledadDocument
+        :type doc: Document
         :return: A deferred whose callback will be invoked with a JSON string
             containing the ciphertext as the value of "raw" key.
         :rtype: twisted.internet.defer.Deferred
@@ -159,7 +159,7 @@ class SoledadCrypto(object):
         the decrypted cleartext content from the encrypted document.
 
         :param doc: the document to be decrypted.
-        :type doc: SoledadDocument
+        :type doc: Document
         :return: The decrypted cleartext content of the document.
         :rtype: str
         """
@@ -225,7 +225,7 @@ def decrypt_sym(data, key, iv, method=ENC_METHOD.aes_256_gcm):
 class BlobEncryptor(object):
     """
     Produces encrypted data from the cleartext data associated with a given
-    SoledadDocument using AES-256 cipher in GCM mode.
+    Document using AES-256 cipher in GCM mode.
 
     The production happens using a Twisted's FileBodyProducer, which uses a
     Cooperator to schedule calls and can be paused/resumed. Each call takes at
diff --git a/client/src/leap/soledad/client/_database/__init__.py b/client/src/leap/soledad/client/_database/__init__.py
new file mode 100644
index 00000000..e69de29b
--- /dev/null
+++ b/client/src/leap/soledad/client/_database/__init__.py
diff --git a/client/src/leap/soledad/client/adbapi.py b/client/src/leap/soledad/client/_database/adbapi.py
index b002055e..5c28d108 100644
--- a/client/src/leap/soledad/client/adbapi.py
+++ b/client/src/leap/soledad/client/_database/adbapi.py
@@ -30,8 +30,9 @@ from zope.proxy import ProxyBase, setProxiedObject
 
 from leap.soledad.common.log import getLogger
 from leap.soledad.common.errors import DatabaseAccessError
-from leap.soledad.client import sqlcipher as soledad_sqlcipher
-from leap.soledad.client.pragmas import set_init_pragmas
+
+from . import sqlcipher
+from . import pragmas
 
 if sys.version_info[0] < 3:
     from pysqlcipher import dbapi2
@@ -73,7 +74,7 @@ def getConnectionPool(opts, openfun=None, driver="pysqlcipher"):
     :rtype: U1DBConnectionPool
     """
     if openfun is None and driver == "pysqlcipher":
-        openfun = partial(set_init_pragmas, opts=opts)
+        openfun = partial(pragmas.set_init_pragmas, opts=opts)
     return U1DBConnectionPool(
         opts,
         # the following params are relayed "as is" to twisted's
@@ -87,7 +88,7 @@ class U1DBConnection(adbapi.Connection):
     A wrapper for a U1DB connection instance.
     """
 
-    u1db_wrapper = soledad_sqlcipher.SoledadSQLCipherWrapper
+    u1db_wrapper = sqlcipher.SoledadSQLCipherWrapper
     """
     The U1DB wrapper to use.
     """
diff --git a/client/src/leap/soledad/client/_blobs.py b/client/src/leap/soledad/client/_database/blobs.py
index 1475b302..79404bf3 100644
--- a/client/src/leap/soledad/client/_blobs.py
+++ b/client/src/leap/soledad/client/_database/blobs.py
@@ -20,8 +20,9 @@ Clientside BlobBackend Storage.
 
 from urlparse import urljoin
 
+import binascii
+import errno
 import os
-import uuid
 import base64
 
 from io import BytesIO
@@ -34,13 +35,18 @@ from twisted.web.client import FileBodyProducer
 
 import treq
 
-from leap.soledad.client.sqlcipher import SQLCipherOptions
-from leap.soledad.client import pragmas
-from leap.soledad.client._pipes import TruncatedTailPipe, PreamblePipe
 from leap.soledad.common.errors import SoledadError
 
-from _crypto import DocInfo, BlobEncryptor, BlobDecryptor
-from _http import HTTPClient
+from .._document import BlobDoc
+from .._crypto import DocInfo
+from .._crypto import BlobEncryptor
+from .._crypto import BlobDecryptor
+from .._http import HTTPClient
+from .._pipes import TruncatedTailPipe
+from .._pipes import PreamblePipe
+
+from . import pragmas
+from . import sqlcipher
 
 
 logger = Logger()
@@ -129,6 +135,16 @@ class DecrypterBuffer(object):
         return self.decrypter._end_stream(), real_size
 
 
+def mkdir_p(path):
+    try:
+        os.makedirs(path)
+    except OSError as exc:
+        if exc.errno == errno.EEXIST and os.path.isdir(path):
+            pass
+        else:
+            raise
+
+
 class BlobManager(object):
     """
     Ideally, the decrypting flow goes like this:
@@ -149,6 +165,7 @@ class BlobManager(object):
             self, local_path, remote, key, secret, user, token=None,
             cert_file=None):
         if local_path:
+            mkdir_p(os.path.dirname(local_path))
             self.local = SQLiteBlobBackend(local_path, key)
         self.remote = remote
         self.secret = secret
@@ -280,10 +297,13 @@ class SQLiteBlobBackend(object):
     def __init__(self, path, key=None):
         self.path = os.path.abspath(
             os.path.join(path, 'soledad_blob.db'))
+        mkdir_p(os.path.dirname(self.path))
         if not key:
             raise ValueError('key cannot be None')
         backend = 'pysqlcipher.dbapi2'
-        opts = SQLCipherOptions('/tmp/ignored', key)
+        opts = sqlcipher.SQLCipherOptions(
+            '/tmp/ignored', binascii.b2a_hex(key),
+            is_raw_key=True, create=True)
         pragmafun = partial(pragmas.set_init_pragmas, opts=opts)
         openfun = _sqlcipherInitFactory(pragmafun)
 
@@ -292,7 +312,11 @@ class SQLiteBlobBackend(object):
             cp_openfun=openfun, cp_min=1, cp_max=2, cp_name='blob_pool')
 
     def close(self):
-        return self.dbpool.close()
+        from twisted._threads import AlreadyQuit
+        try:
+            self.dbpool.close()
+        except AlreadyQuit:
+            pass
 
     @defer.inlineCallbacks
     def put(self, blob_id, blob_fd, size=None):
@@ -352,20 +376,6 @@ def _sqlcipherInitFactory(fun):
     return _initialize
 
 
-class BlobDoc(object):
-
-    # TODO probably not needed, but convenient for testing for now.
-
-    def __init__(self, content, blob_id):
-
-        self.blob_id = blob_id
-        self.is_blob = True
-        self.blob_fd = content
-        if blob_id is None:
-            blob_id = uuid.uuid4().get_hex()
-        self.blob_id = blob_id
-
-
 #
 # testing facilities
 #
@@ -431,8 +441,7 @@ def testit(reactor):
     # TODO convert these into proper unittests
 
     def _manager():
-        if not os.path.isdir(args.path):
-            os.makedirs(args.path)
+        mkdir_p(os.path.dirname(args.path))
         manager = BlobManager(
             args.path, args.url,
             'A' * 32, args.secret,
diff --git a/client/src/leap/soledad/client/_database/dbschema.sql b/client/src/leap/soledad/client/_database/dbschema.sql
new file mode 100644
index 00000000..ae027fc5
--- /dev/null
+++ b/client/src/leap/soledad/client/_database/dbschema.sql
@@ -0,0 +1,42 @@
+-- Database schema
+CREATE TABLE transaction_log (
+    generation INTEGER PRIMARY KEY AUTOINCREMENT,
+    doc_id TEXT NOT NULL,
+    transaction_id TEXT NOT NULL
+);
+CREATE TABLE document (
+    doc_id TEXT PRIMARY KEY,
+    doc_rev TEXT NOT NULL,
+    content TEXT
+);
+CREATE TABLE document_fields (
+    doc_id TEXT NOT NULL,
+    field_name TEXT NOT NULL,
+    value TEXT
+);
+CREATE INDEX document_fields_field_value_doc_idx
+    ON document_fields(field_name, value, doc_id);
+
+CREATE TABLE sync_log (
+    replica_uid TEXT PRIMARY KEY,
+    known_generation INTEGER,
+    known_transaction_id TEXT
+);
+CREATE TABLE conflicts (
+    doc_id TEXT,
+    doc_rev TEXT,
+    content TEXT,
+    CONSTRAINT conflicts_pkey PRIMARY KEY (doc_id, doc_rev)
+);
+CREATE TABLE index_definitions (
+    name TEXT,
+    offset INT,
+    field TEXT,
+    CONSTRAINT index_definitions_pkey PRIMARY KEY (name, offset)
+);
+create index index_definitions_field on index_definitions(field);
+CREATE TABLE u1db_config (
+    name TEXT PRIMARY KEY,
+    value TEXT
+);
+INSERT INTO u1db_config VALUES ('sql_schema', '0');
diff --git a/client/src/leap/soledad/client/pragmas.py b/client/src/leap/soledad/client/_database/pragmas.py
index 870ed63e..870ed63e 100644
--- a/client/src/leap/soledad/client/pragmas.py
+++ b/client/src/leap/soledad/client/_database/pragmas.py
diff --git a/client/src/leap/soledad/client/sqlcipher.py b/client/src/leap/soledad/client/_database/sqlcipher.py
index 2c995d5a..d22017bd 100644
--- a/client/src/leap/soledad/client/sqlcipher.py
+++ b/client/src/leap/soledad/client/_database/sqlcipher.py
@@ -50,16 +50,16 @@ from twisted.internet import reactor
 from twisted.internet import defer
 from twisted.enterprise import adbapi
 
-from leap.soledad.common.document import SoledadDocument
 from leap.soledad.common.log import getLogger
 from leap.soledad.common.l2db import errors as u1db_errors
-from leap.soledad.common.l2db import Document
-from leap.soledad.common.l2db.backends import sqlite_backend
 from leap.soledad.common.errors import DatabaseAccessError
 
 from leap.soledad.client.http_target import SoledadHTTPSyncTarget
 from leap.soledad.client.sync import SoledadSynchronizer
-from leap.soledad.client import pragmas
+
+from .._document import Document
+from . import sqlite
+from . import pragmas
 
 if sys.version_info[0] < 3:
     from pysqlcipher import dbapi2 as sqlcipher_dbapi2
@@ -69,8 +69,8 @@ else:
 logger = getLogger(__name__)
 
 
-# Monkey-patch u1db.backends.sqlite_backend with pysqlcipher.dbapi2
-sqlite_backend.dbapi2 = sqlcipher_dbapi2
+# Monkey-patch u1db.backends.sqlite with pysqlcipher.dbapi2
+sqlite.dbapi2 = sqlcipher_dbapi2
 
 
 # we may want to collect statistics from the sync process
@@ -193,7 +193,7 @@ class SQLCipherOptions(object):
 # The SQLCipher database
 #
 
-class SQLCipherDatabase(sqlite_backend.SQLitePartialExpandDatabase):
+class SQLCipherDatabase(sqlite.SQLitePartialExpandDatabase):
     """
     A U1DB implementation that uses SQLCipher as its persistence layer.
     """
@@ -232,7 +232,7 @@ class SQLCipherDatabase(sqlite_backend.SQLitePartialExpandDatabase):
         # ---------------------------------------------------------
 
         self._ensure_schema()
-        self.set_document_factory(soledad_doc_factory)
+        self.set_document_factory(doc_factory)
         self._prime_replica_uid()
 
     def _prime_replica_uid(self):
@@ -341,7 +341,7 @@ class SQLCipherDatabase(sqlite_backend.SQLitePartialExpandDatabase):
         :param doc: The new version of the document.
         :type doc: u1db.Document
         """
-        sqlite_backend.SQLitePartialExpandDatabase._put_and_update_indexes(
+        sqlite.SQLitePartialExpandDatabase._put_and_update_indexes(
             self, old_doc, doc)
         c = self._db_handle.cursor()
         c.execute('UPDATE document SET syncable=? WHERE doc_id=?',
@@ -361,7 +361,7 @@ class SQLCipherDatabase(sqlite_backend.SQLitePartialExpandDatabase):
         :return: a Document object.
         :type: u1db.Document
         """
-        doc = sqlite_backend.SQLitePartialExpandDatabase._get_doc(
+        doc = sqlite.SQLitePartialExpandDatabase._get_doc(
             self, doc_id, check_for_conflicts)
         if doc:
             c = self._db_handle.cursor()
@@ -437,7 +437,7 @@ class SQLCipherU1DBSync(SQLCipherDatabase):
                 self._opts, check_same_thread=False)
             self._real_replica_uid = None
             self._ensure_schema()
-            self.set_document_factory(soledad_doc_factory)
+            self.set_document_factory(doc_factory)
         except sqlcipher_dbapi2.DatabaseError as e:
             raise DatabaseAccessError(str(e))
 
@@ -505,7 +505,7 @@ class SQLCipherU1DBSync(SQLCipherDatabase):
         return self._get_generation()
 
 
-class U1DBSQLiteBackend(sqlite_backend.SQLitePartialExpandDatabase):
+class U1DBSQLiteBackend(sqlite.SQLitePartialExpandDatabase):
     """
     A very simple wrapper for u1db around sqlcipher backend.
 
@@ -537,7 +537,7 @@ class SoledadSQLCipherWrapper(SQLCipherDatabase):
         self._db_handle = conn
         self._real_replica_uid = None
         self._ensure_schema()
-        self.set_document_factory(soledad_doc_factory)
+        self.set_document_factory(doc_factory)
         self._prime_replica_uid()
 
 
@@ -562,7 +562,7 @@ def _assert_db_is_encrypted(opts):
     # If the regular backend succeeds, then we need to stop because
     # the database was not properly initialized.
     try:
-        sqlite_backend.SQLitePartialExpandDatabase(opts.path)
+        sqlite.SQLitePartialExpandDatabase(opts.path)
     except sqlcipher_dbapi2.DatabaseError:
         # assert that we can access it using SQLCipher with the given
         # key
@@ -583,17 +583,17 @@ class DatabaseIsNotEncrypted(Exception):
     pass
 
 
-def soledad_doc_factory(doc_id=None, rev=None, json='{}', has_conflicts=False,
-                        syncable=True):
+def doc_factory(doc_id=None, rev=None, json='{}', has_conflicts=False,
+                syncable=True):
     """
     Return a default Soledad Document.
     Used in the initialization for SQLCipherDatabase
     """
-    return SoledadDocument(doc_id=doc_id, rev=rev, json=json,
-                           has_conflicts=has_conflicts, syncable=syncable)
+    return Document(doc_id=doc_id, rev=rev, json=json,
+                    has_conflicts=has_conflicts, syncable=syncable)
 
 
-sqlite_backend.SQLiteDatabase.register_implementation(SQLCipherDatabase)
+sqlite.SQLiteDatabase.register_implementation(SQLCipherDatabase)
 
 
 #
diff --git a/client/src/leap/soledad/client/_database/sqlite.py b/client/src/leap/soledad/client/_database/sqlite.py
new file mode 100644
index 00000000..4f7b1259
--- /dev/null
+++ b/client/src/leap/soledad/client/_database/sqlite.py
@@ -0,0 +1,930 @@
+# Copyright 2011 Canonical Ltd.
+# Copyright 2016 LEAP Encryption Access Project
+#
+# 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/>.
+
+"""
+A L2DB implementation that uses SQLite as its persistence layer.
+"""
+
+import errno
+import os
+import json
+import sys
+import time
+import uuid
+import pkg_resources
+
+from sqlite3 import dbapi2
+
+from leap.soledad.common.l2db.backends import CommonBackend, CommonSyncTarget
+from leap.soledad.common.l2db import (
+    Document, errors,
+    query_parser, vectorclock)
+
+
+class SQLiteDatabase(CommonBackend):
+    """A U1DB implementation that uses SQLite as its persistence layer."""
+
+    _sqlite_registry = {}
+
+    def __init__(self, sqlite_file, document_factory=None):
+        """Create a new sqlite file."""
+        self._db_handle = dbapi2.connect(sqlite_file)
+        self._real_replica_uid = None
+        self._ensure_schema()
+        self._factory = document_factory or Document
+
+    def set_document_factory(self, factory):
+        self._factory = factory
+
+    def get_sync_target(self):
+        return SQLiteSyncTarget(self)
+
+    @classmethod
+    def _which_index_storage(cls, c):
+        try:
+            c.execute("SELECT value FROM u1db_config"
+                      " WHERE name = 'index_storage'")
+        except dbapi2.OperationalError as e:
+            # The table does not exist yet
+            return None, e
+        else:
+            return c.fetchone()[0], None
+
+    WAIT_FOR_PARALLEL_INIT_HALF_INTERVAL = 0.5
+
+    @classmethod
+    def _open_database(cls, sqlite_file, document_factory=None):
+        if not os.path.isfile(sqlite_file):
+            raise errors.DatabaseDoesNotExist()
+        tries = 2
+        while True:
+            # Note: There seems to be a bug in sqlite 3.5.9 (with python2.6)
+            #       where without re-opening the database on Windows, it
+            #       doesn't see the transaction that was just committed
+            db_handle = dbapi2.connect(sqlite_file)
+            c = db_handle.cursor()
+            v, err = cls._which_index_storage(c)
+            db_handle.close()
+            if v is not None:
+                break
+            # possibly another process is initializing it, wait for it to be
+            # done
+            if tries == 0:
+                raise err  # go for the richest error?
+            tries -= 1
+            time.sleep(cls.WAIT_FOR_PARALLEL_INIT_HALF_INTERVAL)
+        return SQLiteDatabase._sqlite_registry[v](
+            sqlite_file, document_factory=document_factory)
+
+    @classmethod
+    def open_database(cls, sqlite_file, create, backend_cls=None,
+                      document_factory=None):
+        try:
+            return cls._open_database(
+                sqlite_file, document_factory=document_factory)
+        except errors.DatabaseDoesNotExist:
+            if not create:
+                raise
+            if backend_cls is None:
+                # default is SQLitePartialExpandDatabase
+                backend_cls = SQLitePartialExpandDatabase
+            return backend_cls(sqlite_file, document_factory=document_factory)
+
+    @staticmethod
+    def delete_database(sqlite_file):
+        try:
+            os.unlink(sqlite_file)
+        except OSError as ex:
+            if ex.errno == errno.ENOENT:
+                raise errors.DatabaseDoesNotExist()
+            raise
+
+    @staticmethod
+    def register_implementation(klass):
+        """Register that we implement an SQLiteDatabase.
+
+        The attribute _index_storage_value will be used as the lookup key.
+        """
+        SQLiteDatabase._sqlite_registry[klass._index_storage_value] = klass
+
+    def _get_sqlite_handle(self):
+        """Get access to the underlying sqlite database.
+
+        This should only be used by the test suite, etc, for examining the
+        state of the underlying database.
+        """
+        return self._db_handle
+
+    def _close_sqlite_handle(self):
+        """Release access to the underlying sqlite database."""
+        self._db_handle.close()
+
+    def close(self):
+        self._close_sqlite_handle()
+
+    def _is_initialized(self, c):
+        """Check if this database has been initialized."""
+        c.execute("PRAGMA case_sensitive_like=ON")
+        try:
+            c.execute("SELECT value FROM u1db_config"
+                      " WHERE name = 'sql_schema'")
+        except dbapi2.OperationalError:
+            # The table does not exist yet
+            val = None
+        else:
+            val = c.fetchone()
+        if val is not None:
+            return True
+        return False
+
+    def _initialize(self, c):
+        """Create the schema in the database."""
+        # read the script with sql commands
+        # TODO: Change how we set up the dependency. Most likely use something
+        #   like lp:dirspec to grab the file from a common resource
+        #   directory. Doesn't specifically need to be handled until we get
+        #   to the point of packaging this.
+        schema_content = pkg_resources.resource_string(
+            __name__, 'dbschema.sql')
+        # Note: We'd like to use c.executescript() here, but it seems that
+        #       executescript always commits, even if you set
+        #       isolation_level = None, so if we want to properly handle
+        #       exclusive locking and rollbacks between processes, we need
+        #       to execute it line-by-line
+        for line in schema_content.split(';'):
+            if not line:
+                continue
+            c.execute(line)
+        # add extra fields
+        self._extra_schema_init(c)
+        # A unique identifier should be set for this replica. Implementations
+        # don't have to strictly use uuid here, but we do want the uid to be
+        # unique amongst all databases that will sync with each other.
+        # We might extend this to using something with hostname for easier
+        # debugging.
+        self._set_replica_uid_in_transaction(uuid.uuid4().hex)
+        c.execute("INSERT INTO u1db_config VALUES" " ('index_storage', ?)",
+                  (self._index_storage_value,))
+
+    def _ensure_schema(self):
+        """Ensure that the database schema has been created."""
+        old_isolation_level = self._db_handle.isolation_level
+        c = self._db_handle.cursor()
+        if self._is_initialized(c):
+            return
+        try:
+            # autocommit/own mgmt of transactions
+            self._db_handle.isolation_level = None
+            with self._db_handle:
+                # only one execution path should initialize the db
+                c.execute("begin exclusive")
+                if self._is_initialized(c):
+                    return
+                self._initialize(c)
+        finally:
+            self._db_handle.isolation_level = old_isolation_level
+
+    def _extra_schema_init(self, c):
+        """Add any extra fields, etc to the basic table definitions."""
+
+    def _parse_index_definition(self, index_field):
+        """Parse a field definition for an index, returning a Getter."""
+        # Note: We may want to keep a Parser object around, and cache the
+        #       Getter objects for a greater length of time. Specifically, if
+        #       you create a bunch of indexes, and then insert 50k docs, you'll
+        #       re-parse the indexes between puts. The time to insert the docs
+        #       is still likely to dominate put_doc time, though.
+        parser = query_parser.Parser()
+        getter = parser.parse(index_field)
+        return getter
+
+    def _update_indexes(self, doc_id, raw_doc, getters, db_cursor):
+        """Update document_fields for a single document.
+
+        :param doc_id: Identifier for this document
+        :param raw_doc: The python dict representation of the document.
+        :param getters: A list of [(field_name, Getter)]. Getter.get will be
+            called to evaluate the index definition for this document, and the
+            results will be inserted into the db.
+        :param db_cursor: An sqlite Cursor.
+        :return: None
+        """
+        values = []
+        for field_name, getter in getters:
+            for idx_value in getter.get(raw_doc):
+                values.append((doc_id, field_name, idx_value))
+        if values:
+            db_cursor.executemany(
+                "INSERT INTO document_fields VALUES (?, ?, ?)", values)
+
+    def _set_replica_uid(self, replica_uid):
+        """Force the replica_uid to be set."""
+        with self._db_handle:
+            self._set_replica_uid_in_transaction(replica_uid)
+
+    def _set_replica_uid_in_transaction(self, replica_uid):
+        """Set the replica_uid. A transaction should already be held."""
+        c = self._db_handle.cursor()
+        c.execute("INSERT OR REPLACE INTO u1db_config"
+                  " VALUES ('replica_uid', ?)",
+                  (replica_uid,))
+        self._real_replica_uid = replica_uid
+
+    def _get_replica_uid(self):
+        if self._real_replica_uid is not None:
+            return self._real_replica_uid
+        c = self._db_handle.cursor()
+        c.execute("SELECT value FROM u1db_config WHERE name = 'replica_uid'")
+        val = c.fetchone()
+        if val is None:
+            return None
+        self._real_replica_uid = val[0]
+        return self._real_replica_uid
+
+    _replica_uid = property(_get_replica_uid)
+
+    def _get_generation(self):
+        c = self._db_handle.cursor()
+        c.execute('SELECT max(generation) FROM transaction_log')
+        val = c.fetchone()[0]
+        if val is None:
+            return 0
+        return val
+
+    def _get_generation_info(self):
+        c = self._db_handle.cursor()
+        c.execute(
+            'SELECT max(generation), transaction_id FROM transaction_log ')
+        val = c.fetchone()
+        if val[0] is None:
+            return(0, '')
+        return val
+
+    def _get_trans_id_for_gen(self, generation):
+        if generation == 0:
+            return ''
+        c = self._db_handle.cursor()
+        c.execute(
+            'SELECT transaction_id FROM transaction_log WHERE generation = ?',
+            (generation,))
+        val = c.fetchone()
+        if val is None:
+            raise errors.InvalidGeneration
+        return val[0]
+
+    def _get_transaction_log(self):
+        c = self._db_handle.cursor()
+        c.execute("SELECT doc_id, transaction_id FROM transaction_log"
+                  " ORDER BY generation")
+        return c.fetchall()
+
+    def _get_doc(self, doc_id, check_for_conflicts=False):
+        """Get just the document content, without fancy handling."""
+        c = self._db_handle.cursor()
+        if check_for_conflicts:
+            c.execute(
+                "SELECT document.doc_rev, document.content, "
+                "count(conflicts.doc_rev) FROM document LEFT OUTER JOIN "
+                "conflicts ON conflicts.doc_id = document.doc_id WHERE "
+                "document.doc_id = ? GROUP BY document.doc_id, "
+                "document.doc_rev, document.content;", (doc_id,))
+        else:
+            c.execute(
+                "SELECT doc_rev, content, 0 FROM document WHERE doc_id = ?",
+                (doc_id,))
+        val = c.fetchone()
+        if val is None:
+            return None
+        doc_rev, content, conflicts = val
+        doc = self._factory(doc_id, doc_rev, content)
+        doc.has_conflicts = conflicts > 0
+        return doc
+
+    def _has_conflicts(self, doc_id):
+        c = self._db_handle.cursor()
+        c.execute("SELECT 1 FROM conflicts WHERE doc_id = ? LIMIT 1",
+                  (doc_id,))
+        val = c.fetchone()
+        if val is None:
+            return False
+        else:
+            return True
+
+    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):
+        """Get all documents from the database."""
+        generation = self._get_generation()
+        results = []
+        c = self._db_handle.cursor()
+        c.execute(
+            "SELECT document.doc_id, document.doc_rev, document.content, "
+            "count(conflicts.doc_rev) FROM document LEFT OUTER JOIN conflicts "
+            "ON conflicts.doc_id = document.doc_id GROUP BY document.doc_id, "
+            "document.doc_rev, document.content;")
+        rows = c.fetchall()
+        for doc_id, doc_rev, content, conflicts in rows:
+            if content is None and not include_deleted:
+                continue
+            doc = self._factory(doc_id, doc_rev, content)
+            doc.has_conflicts = conflicts > 0
+            results.append(doc)
+        return (generation, results)
+
+    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)
+        with self._db_handle:
+            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 _expand_to_fields(self, doc_id, base_field, raw_doc, save_none):
+        """Convert a dict representation into named fields.
+
+        So something like: {'key1': 'val1', 'key2': 'val2'}
+        gets converted into: [(doc_id, 'key1', 'val1', 0)
+                              (doc_id, 'key2', 'val2', 0)]
+        :param doc_id: Just added to every record.
+        :param base_field: if set, these are nested keys, so each field should
+            be appropriately prefixed.
+        :param raw_doc: The python dictionary.
+        """
+        # TODO: Handle lists
+        values = []
+        for field_name, value in raw_doc.iteritems():
+            if value is None and not save_none:
+                continue
+            if base_field:
+                full_name = base_field + '.' + field_name
+            else:
+                full_name = field_name
+            if value is None or isinstance(value, (int, float, basestring)):
+                values.append((doc_id, full_name, value, len(values)))
+            else:
+                subvalues = self._expand_to_fields(doc_id, full_name, value,
+                                                   save_none)
+                for _, subfield_name, val, _ in subvalues:
+                    values.append((doc_id, subfield_name, val, len(values)))
+        return values
+
+    def _put_and_update_indexes(self, old_doc, doc):
+        """Actually insert a document into the database.
+
+        This both updates the existing documents content, and any indexes that
+        refer to this document.
+        """
+        raise NotImplementedError(self._put_and_update_indexes)
+
+    def whats_changed(self, old_generation=0):
+        c = self._db_handle.cursor()
+        c.execute("SELECT generation, doc_id, transaction_id"
+                  " FROM transaction_log"
+                  " WHERE generation > ? ORDER BY generation DESC",
+                  (old_generation,))
+        results = c.fetchall()
+        cur_gen = old_generation
+        seen = set()
+        changes = []
+        newest_trans_id = ''
+        for generation, doc_id, trans_id in results:
+            if doc_id not in seen:
+                changes.append((doc_id, generation, trans_id))
+                seen.add(doc_id)
+        if changes:
+            cur_gen = changes[0][1]  # max generation
+            newest_trans_id = changes[0][2]
+            changes.reverse()
+        else:
+            c.execute("SELECT generation, transaction_id"
+                      " FROM transaction_log ORDER BY generation DESC LIMIT 1")
+            results = c.fetchone()
+            if not results:
+                cur_gen = 0
+                newest_trans_id = ''
+            else:
+                cur_gen, newest_trans_id = results
+
+        return cur_gen, newest_trans_id, changes
+
+    def delete_doc(self, doc):
+        with self._db_handle:
+            old_doc = self._get_doc(doc.doc_id, check_for_conflicts=True)
+            if old_doc is None:
+                raise errors.DocumentDoesNotExist
+            if old_doc.rev != doc.rev:
+                raise errors.RevisionConflict()
+            if old_doc.is_tombstone():
+                raise errors.DocumentAlreadyDeleted
+            if old_doc.has_conflicts:
+                raise errors.ConflictedDoc()
+            new_rev = self._allocate_doc_rev(doc.rev)
+            doc.rev = new_rev
+            doc.make_tombstone()
+            self._put_and_update_indexes(old_doc, doc)
+        return new_rev
+
+    def _get_conflicts(self, doc_id):
+        c = self._db_handle.cursor()
+        c.execute("SELECT doc_rev, content FROM conflicts WHERE doc_id = ?",
+                  (doc_id,))
+        return [self._factory(doc_id, doc_rev, content)
+                for doc_rev, content in c.fetchall()]
+
+    def get_doc_conflicts(self, doc_id):
+        with self._db_handle:
+            conflict_docs = self._get_conflicts(doc_id)
+            if not conflict_docs:
+                return []
+            this_doc = self._get_doc(doc_id)
+            this_doc.has_conflicts = True
+            return [this_doc] + conflict_docs
+
+    def _get_replica_gen_and_trans_id(self, other_replica_uid):
+        c = self._db_handle.cursor()
+        c.execute("SELECT known_generation, known_transaction_id FROM sync_log"
+                  " WHERE replica_uid = ?",
+                  (other_replica_uid,))
+        val = c.fetchone()
+        if val is None:
+            other_gen = 0
+            trans_id = ''
+        else:
+            other_gen = val[0]
+            trans_id = val[1]
+        return other_gen, trans_id
+
+    def _set_replica_gen_and_trans_id(self, other_replica_uid,
+                                      other_generation, other_transaction_id):
+        with self._db_handle:
+            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):
+            c = self._db_handle.cursor()
+            c.execute("INSERT OR REPLACE INTO sync_log VALUES (?, ?, ?)",
+                      (other_replica_uid, other_generation,
+                       other_transaction_id))
+
+    def _put_doc_if_newer(self, doc, save_conflict, replica_uid=None,
+                          replica_gen=None, replica_trans_id=None):
+        return super(SQLiteDatabase, self)._put_doc_if_newer(
+            doc,
+            save_conflict=save_conflict,
+            replica_uid=replica_uid, replica_gen=replica_gen,
+            replica_trans_id=replica_trans_id)
+
+    def _add_conflict(self, c, doc_id, my_doc_rev, my_content):
+        c.execute("INSERT INTO conflicts VALUES (?, ?, ?)",
+                  (doc_id, my_doc_rev, my_content))
+
+    def _delete_conflicts(self, c, doc, conflict_revs):
+        deleting = [(doc.doc_id, c_rev) for c_rev in conflict_revs]
+        c.executemany("DELETE FROM conflicts"
+                      " WHERE doc_id=? AND doc_rev=?", deleting)
+        doc.has_conflicts = self._has_conflicts(doc.doc_id)
+
+    def _prune_conflicts(self, doc, doc_vcr):
+        if self._has_conflicts(doc.doc_id):
+            autoresolved = False
+            c_revs_to_prune = []
+            for c_doc in self._get_conflicts(doc.doc_id):
+                c_vcr = vectorclock.VectorClockRev(c_doc.rev)
+                if doc_vcr.is_newer(c_vcr):
+                    c_revs_to_prune.append(c_doc.rev)
+                elif doc.same_content_as(c_doc):
+                    c_revs_to_prune.append(c_doc.rev)
+                    doc_vcr.maximize(c_vcr)
+                    autoresolved = True
+            if autoresolved:
+                doc_vcr.increment(self._replica_uid)
+                doc.rev = doc_vcr.as_str()
+            c = self._db_handle.cursor()
+            self._delete_conflicts(c, doc, c_revs_to_prune)
+
+    def _force_doc_sync_conflict(self, doc):
+        my_doc = self._get_doc(doc.doc_id)
+        c = self._db_handle.cursor()
+        self._prune_conflicts(doc, vectorclock.VectorClockRev(doc.rev))
+        self._add_conflict(c, doc.doc_id, my_doc.rev, my_doc.get_json())
+        doc.has_conflicts = True
+        self._put_and_update_indexes(my_doc, doc)
+
+    def resolve_doc(self, doc, conflicted_doc_revs):
+        with self._db_handle:
+            cur_doc = self._get_doc(doc.doc_id)
+            # TODO: https://bugs.launchpad.net/u1db/+bug/928274
+            #       I think we have a logic bug in resolve_doc
+            #       Specifically, cur_doc.rev is always in the final vector
+            #       clock of revisions that we supersede, even if it wasn't in
+            #       conflicted_doc_revs. We still add it as a conflict, but the
+            #       fact that _put_doc_if_newer propagates resolutions means I
+            #       think that conflict could accidentally be resolved. We need
+            #       to add a test for this case first. (create a rev, create a
+            #       conflict, create another conflict, resolve the first rev
+            #       and first conflict, then make sure that the resolved
+            #       rev doesn't supersede the second conflict rev.) It *might*
+            #       not matter, because the superseding rev is in as a
+            #       conflict, but it does seem incorrect
+            new_rev = self._ensure_maximal_rev(cur_doc.rev,
+                                               conflicted_doc_revs)
+            superseded_revs = set(conflicted_doc_revs)
+            c = self._db_handle.cursor()
+            doc.rev = new_rev
+            if cur_doc.rev in superseded_revs:
+                self._put_and_update_indexes(cur_doc, doc)
+            else:
+                self._add_conflict(c, doc.doc_id, new_rev, doc.get_json())
+            # TODO: Is there some way that we could construct a rev that would
+            #       end up in superseded_revs, such that we add a conflict, and
+            #       then immediately delete it?
+            self._delete_conflicts(c, doc, superseded_revs)
+
+    def list_indexes(self):
+        """Return the list of indexes and their definitions."""
+        c = self._db_handle.cursor()
+        # TODO: How do we test the ordering?
+        c.execute("SELECT name, field FROM index_definitions"
+                  " ORDER BY name, offset")
+        definitions = []
+        cur_name = None
+        for name, field in c.fetchall():
+            if cur_name != name:
+                definitions.append((name, []))
+                cur_name = name
+            definitions[-1][-1].append(field)
+        return definitions
+
+    def _get_index_definition(self, index_name):
+        """Return the stored definition for a given index_name."""
+        c = self._db_handle.cursor()
+        c.execute("SELECT field FROM index_definitions"
+                  " WHERE name = ? ORDER BY offset", (index_name,))
+        fields = [x[0] for x in c.fetchall()]
+        if not fields:
+            raise errors.IndexDoesNotExist
+        return fields
+
+    @staticmethod
+    def _strip_glob(value):
+        """Remove the trailing * from a value."""
+        assert value[-1] == '*'
+        return value[:-1]
+
+    def _format_query(self, definition, key_values):
+        # First, build the definition. We join the document_fields table
+        # against itself, as many times as the 'width' of our definition.
+        # We then do a query for each key_value, one-at-a-time.
+        # Note: All of these strings are static, we could cache them, etc.
+        tables = ["document_fields d%d" % i for i in range(len(definition))]
+        novalue_where = ["d.doc_id = d%d.doc_id"
+                         " AND d%d.field_name = ?"
+                         % (i, i) for i in range(len(definition))]
+        wildcard_where = [novalue_where[i] +
+                          (" AND d%d.value NOT NULL" % (i,))
+                          for i in range(len(definition))]
+        exact_where = [novalue_where[i] +
+                       (" AND d%d.value = ?" % (i,))
+                       for i in range(len(definition))]
+        like_where = [novalue_where[i] +
+                      (" AND d%d.value GLOB ?" % (i,))
+                      for i in range(len(definition))]
+        is_wildcard = False
+        # Merge the lists together, so that:
+        # [field1, field2, field3], [val1, val2, val3]
+        # Becomes:
+        # (field1, val1, field2, val2, field3, val3)
+        args = []
+        where = []
+        for idx, (field, value) in enumerate(zip(definition, key_values)):
+            args.append(field)
+            if value.endswith('*'):
+                if value == '*':
+                    where.append(wildcard_where[idx])
+                else:
+                    # This is a glob match
+                    if is_wildcard:
+                        # We can't have a partial wildcard following
+                        # another wildcard
+                        raise errors.InvalidGlobbing
+                    where.append(like_where[idx])
+                    args.append(value)
+                is_wildcard = True
+            else:
+                if is_wildcard:
+                    raise errors.InvalidGlobbing
+                where.append(exact_where[idx])
+                args.append(value)
+        statement = (
+            "SELECT d.doc_id, d.doc_rev, d.content, count(c.doc_rev) FROM "
+            "document d, %s LEFT OUTER JOIN conflicts c ON c.doc_id = "
+            "d.doc_id WHERE %s GROUP BY d.doc_id, d.doc_rev, d.content ORDER "
+            "BY %s;" % (', '.join(tables), ' AND '.join(where), ', '.join(
+                ['d%d.value' % i for i in range(len(definition))])))
+        return statement, args
+
+    def get_from_index(self, index_name, *key_values):
+        definition = self._get_index_definition(index_name)
+        if len(key_values) != len(definition):
+            raise errors.InvalidValueForIndex()
+        statement, args = self._format_query(definition, key_values)
+        c = self._db_handle.cursor()
+        try:
+            c.execute(statement, tuple(args))
+        except dbapi2.OperationalError as e:
+            raise dbapi2.OperationalError(
+                str(e) +
+                '\nstatement: %s\nargs: %s\n' % (statement, args))
+        res = c.fetchall()
+        results = []
+        for row in res:
+            doc = self._factory(row[0], row[1], row[2])
+            doc.has_conflicts = row[3] > 0
+            results.append(doc)
+        return results
+
+    def _format_range_query(self, definition, start_value, end_value):
+        tables = ["document_fields d%d" % i for i in range(len(definition))]
+        novalue_where = [
+            "d.doc_id = d%d.doc_id AND d%d.field_name = ?" % (i, i) for i in
+            range(len(definition))]
+        wildcard_where = [
+            novalue_where[i] + (" AND d%d.value NOT NULL" % (i,)) for i in
+            range(len(definition))]
+        like_where = [
+            novalue_where[i] + (
+                " AND (d%d.value < ? OR d%d.value GLOB ?)" % (i, i)) for i in
+            range(len(definition))]
+        range_where_lower = [
+            novalue_where[i] + (" AND d%d.value >= ?" % (i,)) for i in
+            range(len(definition))]
+        range_where_upper = [
+            novalue_where[i] + (" AND d%d.value <= ?" % (i,)) for i in
+            range(len(definition))]
+        args = []
+        where = []
+        if start_value:
+            if isinstance(start_value, basestring):
+                start_value = (start_value,)
+            if len(start_value) != len(definition):
+                raise errors.InvalidValueForIndex()
+            is_wildcard = False
+            for idx, (field, value) in enumerate(zip(definition, start_value)):
+                args.append(field)
+                if value.endswith('*'):
+                    if value == '*':
+                        where.append(wildcard_where[idx])
+                    else:
+                        # This is a glob match
+                        if is_wildcard:
+                            # We can't have a partial wildcard following
+                            # another wildcard
+                            raise errors.InvalidGlobbing
+                        where.append(range_where_lower[idx])
+                        args.append(self._strip_glob(value))
+                    is_wildcard = True
+                else:
+                    if is_wildcard:
+                        raise errors.InvalidGlobbing
+                    where.append(range_where_lower[idx])
+                    args.append(value)
+        if end_value:
+            if isinstance(end_value, basestring):
+                end_value = (end_value,)
+            if len(end_value) != len(definition):
+                raise errors.InvalidValueForIndex()
+            is_wildcard = False
+            for idx, (field, value) in enumerate(zip(definition, end_value)):
+                args.append(field)
+                if value.endswith('*'):
+                    if value == '*':
+                        where.append(wildcard_where[idx])
+                    else:
+                        # This is a glob match
+                        if is_wildcard:
+                            # We can't have a partial wildcard following
+                            # another wildcard
+                            raise errors.InvalidGlobbing
+                        where.append(like_where[idx])
+                        args.append(self._strip_glob(value))
+                        args.append(value)
+                    is_wildcard = True
+                else:
+                    if is_wildcard:
+                        raise errors.InvalidGlobbing
+                    where.append(range_where_upper[idx])
+                    args.append(value)
+        statement = (
+            "SELECT d.doc_id, d.doc_rev, d.content, count(c.doc_rev) FROM "
+            "document d, %s LEFT OUTER JOIN conflicts c ON c.doc_id = "
+            "d.doc_id WHERE %s GROUP BY d.doc_id, d.doc_rev, d.content ORDER "
+            "BY %s;" % (', '.join(tables), ' AND '.join(where), ', '.join(
+                ['d%d.value' % i for i in range(len(definition))])))
+        return statement, args
+
+    def get_range_from_index(self, index_name, start_value=None,
+                             end_value=None):
+        """Return all documents with key values in the specified range."""
+        definition = self._get_index_definition(index_name)
+        statement, args = self._format_range_query(
+            definition, start_value, end_value)
+        c = self._db_handle.cursor()
+        try:
+            c.execute(statement, tuple(args))
+        except dbapi2.OperationalError as e:
+            raise dbapi2.OperationalError(
+                str(e) +
+                '\nstatement: %s\nargs: %s\n' % (statement, args))
+        res = c.fetchall()
+        results = []
+        for row in res:
+            doc = self._factory(row[0], row[1], row[2])
+            doc.has_conflicts = row[3] > 0
+            results.append(doc)
+        return results
+
+    def get_index_keys(self, index_name):
+        c = self._db_handle.cursor()
+        definition = self._get_index_definition(index_name)
+        value_fields = ', '.join([
+            'd%d.value' % i for i in range(len(definition))])
+        tables = ["document_fields d%d" % i for i in range(len(definition))]
+        novalue_where = [
+            "d.doc_id = d%d.doc_id AND d%d.field_name = ?" % (i, i) for i in
+            range(len(definition))]
+        where = [
+            novalue_where[i] + (" AND d%d.value NOT NULL" % (i,)) for i in
+            range(len(definition))]
+        statement = (
+            "SELECT %s FROM document d, %s WHERE %s GROUP BY %s;" % (
+                value_fields, ', '.join(tables), ' AND '.join(where),
+                value_fields))
+        try:
+            c.execute(statement, tuple(definition))
+        except dbapi2.OperationalError as e:
+            raise dbapi2.OperationalError(
+                str(e) +
+                '\nstatement: %s\nargs: %s\n' % (statement, tuple(definition)))
+        return c.fetchall()
+
+    def delete_index(self, index_name):
+        with self._db_handle:
+            c = self._db_handle.cursor()
+            c.execute("DELETE FROM index_definitions WHERE name = ?",
+                      (index_name,))
+            c.execute(
+                "DELETE FROM document_fields WHERE document_fields.field_name "
+                " NOT IN (SELECT field from index_definitions)")
+
+
+class SQLiteSyncTarget(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_replica_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_replica_transaction_id)
+
+
+class SQLitePartialExpandDatabase(SQLiteDatabase):
+    """An SQLite Backend that expands documents into a document_field table.
+
+    It stores the original document text in document.doc. For fields that are
+    indexed, the data goes into document_fields.
+    """
+
+    _index_storage_value = 'expand referenced'
+
+    def _get_indexed_fields(self):
+        """Determine what fields are indexed."""
+        c = self._db_handle.cursor()
+        c.execute("SELECT field FROM index_definitions")
+        return set([x[0] for x in c.fetchall()])
+
+    def _evaluate_index(self, raw_doc, field):
+        parser = query_parser.Parser()
+        getter = parser.parse(field)
+        return getter.get(raw_doc)
+
+    def _put_and_update_indexes(self, old_doc, doc):
+        c = self._db_handle.cursor()
+        if doc and not doc.is_tombstone():
+            raw_doc = json.loads(doc.get_json())
+        else:
+            raw_doc = {}
+        if old_doc is not None:
+            c.execute("UPDATE document SET doc_rev=?, content=?"
+                      " WHERE doc_id = ?",
+                      (doc.rev, doc.get_json(), doc.doc_id))
+            c.execute("DELETE FROM document_fields WHERE doc_id = ?",
+                      (doc.doc_id,))
+        else:
+            c.execute("INSERT INTO document (doc_id, doc_rev, content)"
+                      " VALUES (?, ?, ?)",
+                      (doc.doc_id, doc.rev, doc.get_json()))
+        indexed_fields = self._get_indexed_fields()
+        if indexed_fields:
+            # It is expected that len(indexed_fields) is shorter than
+            # len(raw_doc)
+            getters = [(field, self._parse_index_definition(field))
+                       for field in indexed_fields]
+            self._update_indexes(doc.doc_id, raw_doc, getters, c)
+        trans_id = self._allocate_transaction_id()
+        c.execute("INSERT INTO transaction_log(doc_id, transaction_id)"
+                  " VALUES (?, ?)", (doc.doc_id, trans_id))
+
+    def create_index(self, index_name, *index_expressions):
+        with self._db_handle:
+            c = self._db_handle.cursor()
+            cur_fields = self._get_indexed_fields()
+            definition = [(index_name, idx, field)
+                          for idx, field in enumerate(index_expressions)]
+            try:
+                c.executemany("INSERT INTO index_definitions VALUES (?, ?, ?)",
+                              definition)
+            except dbapi2.IntegrityError as e:
+                stored_def = self._get_index_definition(index_name)
+                if stored_def == [x[-1] for x in definition]:
+                    return
+                raise errors.IndexNameTakenError(
+                    str(e) +
+                    str(sys.exc_info()[2])
+                )
+            new_fields = set(
+                [f for f in index_expressions if f not in cur_fields])
+            if new_fields:
+                self._update_all_indexes(new_fields)
+
+    def _iter_all_docs(self):
+        c = self._db_handle.cursor()
+        c.execute("SELECT doc_id, content FROM document")
+        while True:
+            next_rows = c.fetchmany()
+            if not next_rows:
+                break
+            for row in next_rows:
+                yield row
+
+    def _update_all_indexes(self, new_fields):
+        """Iterate all the documents, and add content to document_fields.
+
+        :param new_fields: The index definitions that need to be added.
+        """
+        getters = [(field, self._parse_index_definition(field))
+                   for field in new_fields]
+        c = self._db_handle.cursor()
+        for doc_id, doc in self._iter_all_docs():
+            if doc is None:
+                continue
+            raw_doc = json.loads(doc)
+            self._update_indexes(doc_id, raw_doc, getters, c)
+
+
+SQLiteDatabase.register_implementation(SQLitePartialExpandDatabase)
diff --git a/client/src/leap/soledad/client/_document.py b/client/src/leap/soledad/client/_document.py
new file mode 100644
index 00000000..9ba08e93
--- /dev/null
+++ b/client/src/leap/soledad/client/_document.py
@@ -0,0 +1,253 @@
+# -*- coding: utf-8 -*-
+# _document.py
+# Copyright (C) 2017 LEAP
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# 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/>.
+"""
+Everything related to documents.
+"""
+
+import enum
+import weakref
+import uuid
+
+from twisted.internet import defer
+
+from zope.interface import Interface
+from zope.interface import implementer
+
+from leap.soledad.common.document import SoledadDocument
+
+
+class IDocumentWithAttachment(Interface):
+    """
+    A document that can have an attachment.
+    """
+
+    def set_store(self, store):
+        """
+        Set the store used by this file to manage attachments.
+
+        :param store: The store used to manage attachments.
+        :type store: Soledad
+        """
+
+    def put_attachment(self, fd):
+        """
+        Attach data to this document.
+
+        Add the attachment to local storage, enqueue for upload.
+
+        The document content will be updated with a pointer to the attachment,
+        but the document has to be manually put in the database to reflect
+        modifications.
+
+        :param fd: A file-like object whose content will be attached to this
+                   document.
+        :type fd: file-like
+
+        :return: A deferred which fires when the attachment has been added to
+                 local storage.
+        :rtype: Deferred
+        """
+
+    def get_attachment(self):
+        """
+        Return the data attached to this document.
+
+        If document content contains a pointer to the attachment, try to get
+        the attachment from local storage and, if not found, from remote
+        storage.
+
+        :return: A deferred which fires with a file like-object whose content
+                 is the attachment of this document, or None if nothing is
+                 attached.
+        :rtype: Deferred
+        """
+
+    def delete_attachment(self):
+        """
+        Delete the attachment of this document.
+
+        The pointer to the attachment will be removed from the document
+        content, but the document has to be manually put in the database to
+        reflect modifications.
+
+        :return: A deferred which fires when the attachment has been deleted
+                 from local storage.
+        :rtype: Deferred
+        """
+
+    def attachment_state(self):
+        """
+        Return the state of the attachment of this document.
+
+        The state is a member of AttachmentStates and is of one of NONE,
+        LOCAL, REMOTE or SYNCED.
+
+        :return: A deferred which fires with The state of the attachment of
+                 this document.
+        :rtype: Deferred
+        """
+
+    def is_dirty(self):
+        """
+        Return wether this document's content differs from the contents stored
+        in local database.
+
+        :return: Whether this document is dirty or not.
+        :rtype: bool
+        """
+
+    def upload_attachment(self):
+        """
+        Upload this document's attachment.
+
+        :return: A deferred which fires with the state of the attachment after
+                 it's been uploaded, or NONE if there's no attachment for this
+                 document.
+        :rtype: Deferred
+        """
+
+    def download_attachment(self):
+        """
+        Download this document's attachment.
+
+        :return: A deferred which fires with the state of the attachment after
+                 it's been downloaded, or NONE if there's no attachment for
+                 this document.
+        :rtype: Deferred
+        """
+
+
+class BlobDoc(object):
+
+    # TODO probably not needed, but convenient for testing for now.
+
+    def __init__(self, content, blob_id):
+
+        self.blob_id = blob_id
+        self.is_blob = True
+        self.blob_fd = content
+        if blob_id is None:
+            blob_id = uuid.uuid4().get_hex()
+        self.blob_id = blob_id
+
+
+class AttachmentStates(enum.IntEnum):
+    NONE = 0
+    LOCAL = 1
+    REMOTE = 2
+    SYNCED = 4
+
+
+@implementer(IDocumentWithAttachment)
+class Document(SoledadDocument):
+
+    def __init__(self, doc_id=None, rev=None, json='{}', has_conflicts=False,
+                 syncable=True, store=None):
+        SoledadDocument.__init__(self, doc_id=doc_id, rev=rev, json=json,
+                                 has_conflicts=has_conflicts,
+                                 syncable=syncable)
+        self.set_store(store)
+
+    #
+    # properties
+    #
+
+    @property
+    def _manager(self):
+        if not self.store or not hasattr(self.store, 'blobmanager'):
+            raise Exception('No blob manager found to manage attachments.')
+        return self.store.blobmanager
+
+    @property
+    def _blob_id(self):
+        if self.content and 'blob_id' in self.content:
+            return self.content['blob_id']
+        return None
+
+    def get_store(self):
+        return self._store() if self._store else None
+
+    def set_store(self, store):
+        self._store = weakref.ref(store) if store else None
+
+    store = property(get_store, set_store)
+
+    #
+    # attachment api
+    #
+
+    def put_attachment(self, fd):
+        # add pointer to content
+        blob_id = self._blob_id or str(uuid.uuid4())
+        if not self.content:
+            self.content = {}
+        self.content['blob_id'] = blob_id
+        # put using manager
+        blob = BlobDoc(fd, blob_id)
+        fd.seek(0, 2)
+        size = fd.tell()
+        fd.seek(0)
+        return self._manager.put(blob, size)
+
+    def get_attachment(self):
+        if not self._blob_id:
+            return defer.succeed(None)
+        return self._manager.get(self._blob_id)
+
+    def delete_attachment(self):
+        raise NotImplementedError
+
+    @defer.inlineCallbacks
+    def attachment_state(self):
+        state = AttachmentStates.NONE
+
+        if not self._blob_id:
+            defer.returnValue(state)
+
+        local_list = yield self._manager.local_list()
+        if self._blob_id in local_list:
+            state |= AttachmentStates.LOCAL
+
+        remote_list = yield self._manager.remote_list()
+        if self._blob_id in remote_list:
+            state |= AttachmentStates.REMOTE
+
+        defer.returnValue(state)
+
+    @defer.inlineCallbacks
+    def is_dirty(self):
+        stored = yield self.store.get_doc(self.doc_id)
+        if stored.content != self.content:
+            defer.returnValue(True)
+        defer.returnValue(False)
+
+    @defer.inlineCallbacks
+    def upload_attachment(self):
+        if not self._blob_id:
+            defer.returnValue(AttachmentStates.NONE)
+
+        fd = yield self._manager.get_blob(self._blob_id)
+        # TODO: turn following method into a public one
+        yield self._manager._encrypt_and_upload(self._blob_id, fd)
+        defer.returnValue(self.attachment_state())
+
+    @defer.inlineCallbacks
+    def download_attachment(self):
+        if not self._blob_id:
+            defer.returnValue(None)
+        yield self.get_attachment()
+        defer.returnValue(self.attachment_state())
diff --git a/client/src/leap/soledad/client/_secrets/storage.py b/client/src/leap/soledad/client/_secrets/storage.py
index 6ea89900..85713a48 100644
--- a/client/src/leap/soledad/client/_secrets/storage.py
+++ b/client/src/leap/soledad/client/_secrets/storage.py
@@ -23,8 +23,8 @@ from hashlib import sha256
 from leap.soledad.common import SHARED_DB_NAME
 from leap.soledad.common.log import getLogger
 
-from leap.soledad.common.document import SoledadDocument
 from leap.soledad.client.shared_db import SoledadSharedDatabase
+from leap.soledad.client._document import Document
 from leap.soledad.client._secrets.util import emit, UserDataMixin
 
 
@@ -111,7 +111,7 @@ class SecretsStorage(UserDataMixin):
     def save_remote(self, encrypted):
         doc = self._remote_doc
         if not doc:
-            doc = SoledadDocument(doc_id=self._remote_doc_id())
+            doc = Document(doc_id=self._remote_doc_id())
         doc.content = encrypted
         db = self._shared_db
         if not db:
diff --git a/client/src/leap/soledad/client/api.py b/client/src/leap/soledad/client/api.py
index 18fb35d7..3dd99227 100644
--- a/client/src/leap/soledad/client/api.py
+++ b/client/src/leap/soledad/client/api.py
@@ -51,13 +51,14 @@ from leap.soledad.common.l2db.remote import http_client
 from leap.soledad.common.l2db.remote.ssl_match_hostname import match_hostname
 from leap.soledad.common.errors import DatabaseAccessError
 
-from leap.soledad.client import adbapi
-from leap.soledad.client import events as soledad_events
-from leap.soledad.client import interfaces as soledad_interfaces
-from leap.soledad.client import sqlcipher
-from leap.soledad.client._recovery_code import RecoveryCode
-from leap.soledad.client._secrets import Secrets
-from leap.soledad.client._crypto import SoledadCrypto
+from . import events as soledad_events
+from . import interfaces as soledad_interfaces
+from ._crypto import SoledadCrypto
+from ._database import adbapi
+from ._database import blobs
+from ._database import sqlcipher
+from ._recovery_code import RecoveryCode
+from ._secrets import Secrets
 
 
 logger = getLogger(__name__)
@@ -171,6 +172,7 @@ class Soledad(object):
         self._recovery_code = RecoveryCode()
         self._secrets = Secrets(self)
         self._crypto = SoledadCrypto(self._secrets.remote_secret)
+        self._init_blobmanager()
 
         try:
             # initialize database access, trap any problems so we can shutdown
@@ -262,6 +264,13 @@ class Soledad(object):
                 sync_exchange_phase = _p
         return sync_phase, sync_exchange_phase
 
+    def _init_blobmanager(self):
+        path = os.path.join(os.path.dirname(self._local_db_path), 'blobs')
+        url = urlparse.urljoin(self.server_url, 'blobs/%s' % uuid)
+        key = self._secrets.local_key
+        self.blobmanager = blobs.BlobManager(path, url, key, self.uuid,
+                                             self.token, SOLEDAD_CERT)
+
     #
     # Closing methods
     #
@@ -272,6 +281,7 @@ class Soledad(object):
         """
         logger.debug("closing soledad")
         self._dbpool.close()
+        self.blobmanager.close()
         if getattr(self, '_dbsyncer', None):
             self._dbsyncer.close()
 
@@ -306,7 +316,7 @@ class Soledad(object):
         ============================== WARNING ==============================
 
         :param doc: A document with new content.
-        :type doc: leap.soledad.common.document.SoledadDocument
+        :type doc: leap.soledad.common.document.Document
         :return: A deferred whose callback will be invoked with the new
             revision identifier for the document. The document object will
             also be updated.
@@ -323,7 +333,7 @@ class Soledad(object):
         This will also set doc.content to None.
 
         :param doc: A document to be deleted.
-        :type doc: leap.soledad.common.document.SoledadDocument
+        :type doc: leap.soledad.common.document.Document
         :return: A deferred.
         :rtype: twisted.internet.defer.Deferred
         """
@@ -387,6 +397,7 @@ class Soledad(object):
         """
         return self._defer("get_all_docs", include_deleted)
 
+    @defer.inlineCallbacks
     def create_doc(self, content, doc_id=None):
         """
         Create a new document.
@@ -408,8 +419,9 @@ class Soledad(object):
         # create_doc (and probably to put_doc too). There are cases (mail
         # payloads for example) in which we already have the encoding in the
         # headers, so we don't need to guess it.
-        d = self._defer("create_doc", content, doc_id=doc_id)
-        return d
+        doc = yield self._defer("create_doc", content, doc_id=doc_id)
+        doc.set_store(self)
+        defer.returnValue(doc)
 
     def create_doc_from_json(self, json, doc_id=None):
         """
@@ -590,7 +602,7 @@ class Soledad(object):
         the time you GET_DOC_CONFLICTS until the point where you RESOLVE)
 
         :param doc: A Document with the new content to be inserted.
-        :type doc: SoledadDocument
+        :type doc: Document
         :param conflicted_doc_revs: A list of revisions that the new content
             supersedes.
         :type conflicted_doc_revs: list(str)
diff --git a/client/src/leap/soledad/client/crypto.py b/client/src/leap/soledad/client/crypto.py
index 09e90171..4795846c 100644
--- a/client/src/leap/soledad/client/crypto.py
+++ b/client/src/leap/soledad/client/crypto.py
@@ -167,7 +167,7 @@ class SoledadCrypto(object):
         Wrapper around encrypt_docstr that accepts the document as argument.
 
         :param doc: the document.
-        :type doc: SoledadDocument
+        :type doc: Document
         """
         key = self.doc_passphrase(doc.doc_id)
 
@@ -179,7 +179,7 @@ class SoledadCrypto(object):
         Wrapper around decrypt_doc_dict that accepts the document as argument.
 
         :param doc: the document.
-        :type doc: SoledadDocument
+        :type doc: Document
 
         :return: json string with the decrypted document
         :rtype: str
@@ -194,7 +194,7 @@ class SoledadCrypto(object):
 
 
 #
-# Crypto utilities for a SoledadDocument.
+# Crypto utilities for a Document.
 #
 
 def mac_doc(doc_id, doc_rev, ciphertext, enc_scheme, enc_method, enc_iv,
@@ -439,7 +439,7 @@ def is_symmetrically_encrypted(doc):
     Return True if the document was symmetrically encrypted.
 
     :param doc: The document to check.
-    :type doc: SoledadDocument
+    :type doc: Document
 
     :rtype: bool
     """
diff --git a/client/src/leap/soledad/client/examples/benchmarks/measure_index_times.py b/client/src/leap/soledad/client/examples/benchmarks/measure_index_times.py
index 92bc85d6..276b1200 100644
--- a/client/src/leap/soledad/client/examples/benchmarks/measure_index_times.py
+++ b/client/src/leap/soledad/client/examples/benchmarks/measure_index_times.py
@@ -28,7 +28,7 @@ from twisted.internet import defer, reactor
 
 from leap.soledad.common import l2db
 from leap.soledad.client import adbapi
-from leap.soledad.client.sqlcipher import SQLCipherOptions
+from leap.soledad.client._database.sqlcipher import SQLCipherOptions
 
 
 folder = os.environ.get("TMPDIR", "tmp")
diff --git a/client/src/leap/soledad/client/examples/benchmarks/measure_index_times_custom_docid.py b/client/src/leap/soledad/client/examples/benchmarks/measure_index_times_custom_docid.py
index 429566c7..d288582b 100644
--- a/client/src/leap/soledad/client/examples/benchmarks/measure_index_times_custom_docid.py
+++ b/client/src/leap/soledad/client/examples/benchmarks/measure_index_times_custom_docid.py
@@ -27,7 +27,7 @@ import sys
 from twisted.internet import defer, reactor
 
 from leap.soledad.client import adbapi
-from leap.soledad.client.sqlcipher import SQLCipherOptions
+from leap.soledad.client._database.sqlcipher import SQLCipherOptions
 from leap.soledad.common import l2db
 
 
diff --git a/client/src/leap/soledad/client/examples/use_adbapi.py b/client/src/leap/soledad/client/examples/use_adbapi.py
index 39301b41..25b32307 100644
--- a/client/src/leap/soledad/client/examples/use_adbapi.py
+++ b/client/src/leap/soledad/client/examples/use_adbapi.py
@@ -24,7 +24,7 @@ import os
 from twisted.internet import defer, reactor
 
 from leap.soledad.client import adbapi
-from leap.soledad.client.sqlcipher import SQLCipherOptions
+from leap.soledad.client._database.sqlcipher import SQLCipherOptions
 from leap.soledad.common import l2db
 
 
diff --git a/client/src/leap/soledad/client/http_target/fetch.py b/client/src/leap/soledad/client/http_target/fetch.py
index cf4984d1..9d456830 100644
--- a/client/src/leap/soledad/client/http_target/fetch.py
+++ b/client/src/leap/soledad/client/http_target/fetch.py
@@ -23,10 +23,10 @@ from leap.soledad.client.events import emit_async
 from leap.soledad.client.http_target.support import RequestBody
 from leap.soledad.common.log import getLogger
 from leap.soledad.client._crypto import is_symmetrically_encrypted
-from leap.soledad.common.document import SoledadDocument
 from leap.soledad.common.l2db import errors
 from leap.soledad.client import crypto as old_crypto
 
+from .._document import Document
 from . import fetch_protocol
 
 logger = getLogger(__name__)
@@ -113,7 +113,7 @@ class HTTPDocFetcher(object):
 
     @defer.inlineCallbacks
     def __atomic_doc_parse(self, doc_info, content, total):
-        doc = SoledadDocument(doc_info['id'], doc_info['rev'], content)
+        doc = Document(doc_info['id'], doc_info['rev'], content)
         if is_symmetrically_encrypted(content):
             content = (yield self._crypto.decrypt_doc(doc)).getvalue()
         elif old_crypto.is_symmetrically_encrypted(doc):
diff --git a/client/src/leap/soledad/client/interfaces.py b/client/src/leap/soledad/client/interfaces.py
index 1be47df7..0600449f 100644
--- a/client/src/leap/soledad/client/interfaces.py
+++ b/client/src/leap/soledad/client/interfaces.py
@@ -69,7 +69,7 @@ class ILocalStorage(Interface):
         Update a document in the local encrypted database.
 
         :param doc: the document to update
-        :type doc: SoledadDocument
+        :type doc: Document
 
         :return:
             a deferred that will fire with the new revision identifier for
@@ -82,7 +82,7 @@ class ILocalStorage(Interface):
         Delete a document from the local encrypted database.
 
         :param doc: the document to delete
-        :type doc: SoledadDocument
+        :type doc: Document
 
         :return:
             a deferred that will fire with ...
@@ -102,7 +102,7 @@ class ILocalStorage(Interface):
 
         :return:
             A deferred that will fire with the document object, containing a
-            SoledadDocument, or None if it could not be found
+            Document, or None if it could not be found
         :rtype: Deferred
         """
 
@@ -147,7 +147,7 @@ class ILocalStorage(Interface):
         :type doc_id: str
 
         :return:
-            A deferred tht will fire with the new document (SoledadDocument
+            A deferred tht will fire with the new document (Document
             instance).
         :rtype: Deferred
         """
@@ -167,7 +167,7 @@ class ILocalStorage(Interface):
         :param doc_id: An optional identifier specifying the document id.
         :type doc_id:
         :return:
-            A deferred that will fire with the new document (A SoledadDocument
+            A deferred that will fire with the new document (A Document
             instance)
         :rtype: Deferred
         """
@@ -304,7 +304,7 @@ class ILocalStorage(Interface):
         Mark a document as no longer conflicted.
 
         :param doc: a document with the new content to be inserted.
-        :type doc: SoledadDocument
+        :type doc: Document
         :param conflicted_doc_revs:
             A deferred that will fire with a list of revisions that the new
             content supersedes.