diff --git a/jenkins-unittests.sh b/jenkins-unittests.sh
index 6b0c296cf..4c2f103e8 100755
--- a/jenkins-unittests.sh
+++ b/jenkins-unittests.sh
@@ -25,5 +25,6 @@ rm .coverage* || echo "No coverage files to remove"
 tox --notest -e py27
 TOX_BIN=$WORKSPACE/.tox/py27/bin
 python synapse/python_dependencies.py | xargs -n1 $TOX_BIN/pip install
+$TOX_BIN/pip install lxml
 
 tox -e py27
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index a582d6334..6986930c0 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -741,7 +741,7 @@ class AuthHandler(BaseHandler):
     def set_password(self, user_id, newpassword, requester=None):
         password_hash = self.hash(newpassword)
 
-        except_access_token_ids = [requester.access_token_id] if requester else []
+        except_access_token_id = requester.access_token_id if requester else None
 
         try:
             yield self.store.user_set_password_hash(user_id, password_hash)
@@ -750,10 +750,10 @@ class AuthHandler(BaseHandler):
                 raise SynapseError(404, "Unknown user", Codes.NOT_FOUND)
             raise e
         yield self.store.user_delete_access_tokens(
-            user_id, except_access_token_ids
+            user_id, except_access_token_id
         )
         yield self.hs.get_pusherpool().remove_pushers_by_user(
-            user_id, except_access_token_ids
+            user_id, except_access_token_id
         )
 
     @defer.inlineCallbacks
diff --git a/synapse/handlers/federation.py b/synapse/handlers/federation.py
index ff6bb475b..328f8f484 100644
--- a/synapse/handlers/federation.py
+++ b/synapse/handlers/federation.py
@@ -274,7 +274,7 @@ class FederationHandler(BaseHandler):
 
     @log_function
     @defer.inlineCallbacks
-    def backfill(self, dest, room_id, limit, extremities=[]):
+    def backfill(self, dest, room_id, limit, extremities):
         """ Trigger a backfill request to `dest` for the given `room_id`
 
         This will attempt to get more events from the remote. This may return
@@ -284,9 +284,6 @@ class FederationHandler(BaseHandler):
         if dest == self.server_name:
             raise SynapseError(400, "Can't backfill from self.")
 
-        if not extremities:
-            extremities = yield self.store.get_oldest_events_in_room(room_id)
-
         events = yield self.replication_layer.backfill(
             dest,
             room_id,
@@ -455,6 +452,10 @@ class FederationHandler(BaseHandler):
         )
         max_depth = sorted_extremeties_tuple[0][1]
 
+        # We don't want to specify too many extremities as it causes the backfill
+        # request URI to be too long.
+        extremities = dict(sorted_extremeties_tuple[:5])
+
         if current_depth > max_depth:
             logger.debug(
                 "Not backfilling as we don't need to. %d < %d",
diff --git a/synapse/push/pusherpool.py b/synapse/push/pusherpool.py
index 5853ec36a..54c0f1b84 100644
--- a/synapse/push/pusherpool.py
+++ b/synapse/push/pusherpool.py
@@ -102,14 +102,14 @@ class PusherPool:
                 yield self.remove_pusher(p['app_id'], p['pushkey'], p['user_name'])
 
     @defer.inlineCallbacks
-    def remove_pushers_by_user(self, user_id, except_token_ids=[]):
+    def remove_pushers_by_user(self, user_id, except_access_token_id=None):
         all = yield self.store.get_all_pushers()
         logger.info(
-            "Removing all pushers for user %s except access tokens ids %r",
-            user_id, except_token_ids
+            "Removing all pushers for user %s except access tokens id %r",
+            user_id, except_access_token_id
         )
         for p in all:
-            if p['user_name'] == user_id and p['access_token'] not in except_token_ids:
+            if p['user_name'] == user_id and p['access_token'] != except_access_token_id:
                 logger.info(
                     "Removing pusher for app id %s, pushkey %s, user %s",
                     p['app_id'], p['pushkey'], p['user_name']
diff --git a/synapse/replication/slave/storage/_base.py b/synapse/replication/slave/storage/_base.py
index d839d169a..f19540d6b 100644
--- a/synapse/replication/slave/storage/_base.py
+++ b/synapse/replication/slave/storage/_base.py
@@ -51,6 +51,6 @@ class BaseSlavedStore(SQLBaseStore):
                 try:
                     getattr(self, cache_func).invalidate(tuple(keys))
                 except AttributeError:
-                    logger.warn("Got unexpected cache_func: %r", cache_func)
+                    logger.info("Got unexpected cache_func: %r", cache_func)
             self._cache_id_gen.advance(int(stream["position"]))
         return defer.succeed(None)
diff --git a/synapse/replication/slave/storage/registration.py b/synapse/replication/slave/storage/registration.py
index 307833f9e..38b78b97f 100644
--- a/synapse/replication/slave/storage/registration.py
+++ b/synapse/replication/slave/storage/registration.py
@@ -25,6 +25,6 @@ class SlavedRegistrationStore(BaseSlavedStore):
     # TODO: use the cached version and invalidate deleted tokens
     get_user_by_access_token = RegistrationStore.__dict__[
         "get_user_by_access_token"
-    ].orig
+    ]
 
     _query_for_auth = DataStore._query_for_auth.__func__
diff --git a/synapse/rest/media/v1/preview_url_resource.py b/synapse/rest/media/v1/preview_url_resource.py
index bdd0e60c5..4e4100bde 100644
--- a/synapse/rest/media/v1/preview_url_resource.py
+++ b/synapse/rest/media/v1/preview_url_resource.py
@@ -29,14 +29,13 @@ from synapse.http.server import (
 from synapse.util.async import ObservableDeferred
 from synapse.util.stringutils import is_ascii
 
-from copy import deepcopy
-
 import os
 import re
 import fnmatch
 import cgi
 import ujson as json
 import urlparse
+import itertools
 
 import logging
 logger = logging.getLogger(__name__)
@@ -163,7 +162,7 @@ class PreviewUrlResource(Resource):
 
         logger.debug("got media_info of '%s'" % media_info)
 
-        if self._is_media(media_info['media_type']):
+        if _is_media(media_info['media_type']):
             dims = yield self.media_repo._generate_local_thumbnails(
                 media_info['filesystem_id'], media_info
             )
@@ -184,11 +183,9 @@ class PreviewUrlResource(Resource):
                 logger.warn("Couldn't get dims for %s" % url)
 
             # define our OG response for this media
-        elif self._is_html(media_info['media_type']):
+        elif _is_html(media_info['media_type']):
             # TODO: somehow stop a big HTML tree from exploding synapse's RAM
 
-            from lxml import etree
-
             file = open(media_info['filename'])
             body = file.read()
             file.close()
@@ -199,17 +196,35 @@ class PreviewUrlResource(Resource):
             match = re.match(r'.*; *charset=(.*?)(;|$)', media_info['media_type'], re.I)
             encoding = match.group(1) if match else "utf-8"
 
-            try:
-                parser = etree.HTMLParser(recover=True, encoding=encoding)
-                tree = etree.fromstring(body, parser)
-                og = yield self._calc_og(tree, media_info, requester)
-            except UnicodeDecodeError:
-                # blindly try decoding the body as utf-8, which seems to fix
-                # the charset mismatches on https://google.com
-                parser = etree.HTMLParser(recover=True, encoding=encoding)
-                tree = etree.fromstring(body.decode('utf-8', 'ignore'), parser)
-                og = yield self._calc_og(tree, media_info, requester)
+            og = decode_and_calc_og(body, media_info['uri'], encoding)
 
+            # pre-cache the image for posterity
+            # FIXME: it might be cleaner to use the same flow as the main /preview_url
+            # request itself and benefit from the same caching etc.  But for now we
+            # just rely on the caching on the master request to speed things up.
+            if 'og:image' in og and og['og:image']:
+                image_info = yield self._download_url(
+                    _rebase_url(og['og:image'], media_info['uri']), requester.user
+                )
+
+                if _is_media(image_info['media_type']):
+                    # TODO: make sure we don't choke on white-on-transparent images
+                    dims = yield self.media_repo._generate_local_thumbnails(
+                        image_info['filesystem_id'], image_info
+                    )
+                    if dims:
+                        og["og:image:width"] = dims['width']
+                        og["og:image:height"] = dims['height']
+                    else:
+                        logger.warn("Couldn't get dims for %s" % og["og:image"])
+
+                    og["og:image"] = "mxc://%s/%s" % (
+                        self.server_name, image_info['filesystem_id']
+                    )
+                    og["og:image:type"] = image_info['media_type']
+                    og["matrix:image:size"] = image_info['media_length']
+                else:
+                    del og["og:image"]
         else:
             logger.warn("Failed to find any OG data in %s", url)
             og = {}
@@ -232,139 +247,6 @@ class PreviewUrlResource(Resource):
 
         respond_with_json_bytes(request, 200, json.dumps(og), send_cors=True)
 
-    @defer.inlineCallbacks
-    def _calc_og(self, tree, media_info, requester):
-        # suck our tree into lxml and define our OG response.
-
-        # if we see any image URLs in the OG response, then spider them
-        # (although the client could choose to do this by asking for previews of those
-        # URLs to avoid DoSing the server)
-
-        # "og:type"         : "video",
-        # "og:url"          : "https://www.youtube.com/watch?v=LXDBoHyjmtw",
-        # "og:site_name"    : "YouTube",
-        # "og:video:type"   : "application/x-shockwave-flash",
-        # "og:description"  : "Fun stuff happening here",
-        # "og:title"        : "RemoteJam - Matrix team hack for Disrupt Europe Hackathon",
-        # "og:image"        : "https://i.ytimg.com/vi/LXDBoHyjmtw/maxresdefault.jpg",
-        # "og:video:url"    : "http://www.youtube.com/v/LXDBoHyjmtw?version=3&autohide=1",
-        # "og:video:width"  : "1280"
-        # "og:video:height" : "720",
-        # "og:video:secure_url": "https://www.youtube.com/v/LXDBoHyjmtw?version=3",
-
-        og = {}
-        for tag in tree.xpath("//*/meta[starts-with(@property, 'og:')]"):
-            if 'content' in tag.attrib:
-                og[tag.attrib['property']] = tag.attrib['content']
-
-        # TODO: grab article: meta tags too, e.g.:
-
-        # "article:publisher" : "https://www.facebook.com/thethudonline" />
-        # "article:author" content="https://www.facebook.com/thethudonline" />
-        # "article:tag" content="baby" />
-        # "article:section" content="Breaking News" />
-        # "article:published_time" content="2016-03-31T19:58:24+00:00" />
-        # "article:modified_time" content="2016-04-01T18:31:53+00:00" />
-
-        if 'og:title' not in og:
-            # do some basic spidering of the HTML
-            title = tree.xpath("(//title)[1] | (//h1)[1] | (//h2)[1] | (//h3)[1]")
-            og['og:title'] = title[0].text.strip() if title else None
-
-        if 'og:image' not in og:
-            # TODO: extract a favicon failing all else
-            meta_image = tree.xpath(
-                "//*/meta[translate(@itemprop, 'IMAGE', 'image')='image']/@content"
-            )
-            if meta_image:
-                og['og:image'] = self._rebase_url(meta_image[0], media_info['uri'])
-            else:
-                # TODO: consider inlined CSS styles as well as width & height attribs
-                images = tree.xpath("//img[@src][number(@width)>10][number(@height)>10]")
-                images = sorted(images, key=lambda i: (
-                    -1 * float(i.attrib['width']) * float(i.attrib['height'])
-                ))
-                if not images:
-                    images = tree.xpath("//img[@src]")
-                if images:
-                    og['og:image'] = images[0].attrib['src']
-
-        # pre-cache the image for posterity
-        # FIXME: it might be cleaner to use the same flow as the main /preview_url
-        # request itself and benefit from the same caching etc.  But for now we
-        # just rely on the caching on the master request to speed things up.
-        if 'og:image' in og and og['og:image']:
-            image_info = yield self._download_url(
-                self._rebase_url(og['og:image'], media_info['uri']), requester.user
-            )
-
-            if self._is_media(image_info['media_type']):
-                # TODO: make sure we don't choke on white-on-transparent images
-                dims = yield self.media_repo._generate_local_thumbnails(
-                    image_info['filesystem_id'], image_info
-                )
-                if dims:
-                    og["og:image:width"] = dims['width']
-                    og["og:image:height"] = dims['height']
-                else:
-                    logger.warn("Couldn't get dims for %s" % og["og:image"])
-
-                og["og:image"] = "mxc://%s/%s" % (
-                    self.server_name, image_info['filesystem_id']
-                )
-                og["og:image:type"] = image_info['media_type']
-                og["matrix:image:size"] = image_info['media_length']
-            else:
-                del og["og:image"]
-
-        if 'og:description' not in og:
-            meta_description = tree.xpath(
-                "//*/meta"
-                "[translate(@name, 'DESCRIPTION', 'description')='description']"
-                "/@content")
-            if meta_description:
-                og['og:description'] = meta_description[0]
-            else:
-                # grab any text nodes which are inside the <body/> tag...
-                # unless they are within an HTML5 semantic markup tag...
-                # <header/>, <nav/>, <aside/>, <footer/>
-                # ...or if they are within a <script/> or <style/> tag.
-                # This is a very very very coarse approximation to a plain text
-                # render of the page.
-
-                # We don't just use XPATH here as that is slow on some machines.
-
-                # We clone `tree` as we modify it.
-                cloned_tree = deepcopy(tree.find("body"))
-
-                TAGS_TO_REMOVE = ("header", "nav", "aside", "footer", "script", "style",)
-                for el in cloned_tree.iter(TAGS_TO_REMOVE):
-                    el.getparent().remove(el)
-
-                # Split all the text nodes into paragraphs (by splitting on new
-                # lines)
-                text_nodes = (
-                    re.sub(r'\s+', '\n', el.text).strip()
-                    for el in cloned_tree.iter()
-                    if el.text and isinstance(el.tag, basestring)  # Removes comments
-                )
-                og['og:description'] = summarize_paragraphs(text_nodes)
-
-        # TODO: delete the url downloads to stop diskfilling,
-        # as we only ever cared about its OG
-        defer.returnValue(og)
-
-    def _rebase_url(self, url, base):
-        base = list(urlparse.urlparse(base))
-        url = list(urlparse.urlparse(url))
-        if not url[0]:  # fix up schema
-            url[0] = base[0] or "http"
-        if not url[1]:  # fix up hostname
-            url[1] = base[1]
-            if not url[2].startswith('/'):
-                url[2] = re.sub(r'/[^/]+$', '/', base[2]) + url[2]
-        return urlparse.urlunparse(url)
-
     @defer.inlineCallbacks
     def _download_url(self, url, user):
         # TODO: we should probably honour robots.txt... except in practice
@@ -445,17 +327,171 @@ class PreviewUrlResource(Resource):
             "etag": headers["ETag"][0] if "ETag" in headers else None,
         })
 
-    def _is_media(self, content_type):
-        if content_type.lower().startswith("image/"):
-            return True
 
-    def _is_html(self, content_type):
-        content_type = content_type.lower()
-        if (
-            content_type.startswith("text/html") or
-            content_type.startswith("application/xhtml")
-        ):
-            return True
+def decode_and_calc_og(body, media_uri, request_encoding=None):
+    from lxml import etree
+
+    try:
+        parser = etree.HTMLParser(recover=True, encoding=request_encoding)
+        tree = etree.fromstring(body, parser)
+        og = _calc_og(tree, media_uri)
+    except UnicodeDecodeError:
+        # blindly try decoding the body as utf-8, which seems to fix
+        # the charset mismatches on https://google.com
+        parser = etree.HTMLParser(recover=True, encoding=request_encoding)
+        tree = etree.fromstring(body.decode('utf-8', 'ignore'), parser)
+        og = _calc_og(tree, media_uri)
+
+    return og
+
+
+def _calc_og(tree, media_uri):
+    # suck our tree into lxml and define our OG response.
+
+    # if we see any image URLs in the OG response, then spider them
+    # (although the client could choose to do this by asking for previews of those
+    # URLs to avoid DoSing the server)
+
+    # "og:type"         : "video",
+    # "og:url"          : "https://www.youtube.com/watch?v=LXDBoHyjmtw",
+    # "og:site_name"    : "YouTube",
+    # "og:video:type"   : "application/x-shockwave-flash",
+    # "og:description"  : "Fun stuff happening here",
+    # "og:title"        : "RemoteJam - Matrix team hack for Disrupt Europe Hackathon",
+    # "og:image"        : "https://i.ytimg.com/vi/LXDBoHyjmtw/maxresdefault.jpg",
+    # "og:video:url"    : "http://www.youtube.com/v/LXDBoHyjmtw?version=3&autohide=1",
+    # "og:video:width"  : "1280"
+    # "og:video:height" : "720",
+    # "og:video:secure_url": "https://www.youtube.com/v/LXDBoHyjmtw?version=3",
+
+    og = {}
+    for tag in tree.xpath("//*/meta[starts-with(@property, 'og:')]"):
+        if 'content' in tag.attrib:
+            og[tag.attrib['property']] = tag.attrib['content']
+
+    # TODO: grab article: meta tags too, e.g.:
+
+    # "article:publisher" : "https://www.facebook.com/thethudonline" />
+    # "article:author" content="https://www.facebook.com/thethudonline" />
+    # "article:tag" content="baby" />
+    # "article:section" content="Breaking News" />
+    # "article:published_time" content="2016-03-31T19:58:24+00:00" />
+    # "article:modified_time" content="2016-04-01T18:31:53+00:00" />
+
+    if 'og:title' not in og:
+        # do some basic spidering of the HTML
+        title = tree.xpath("(//title)[1] | (//h1)[1] | (//h2)[1] | (//h3)[1]")
+        og['og:title'] = title[0].text.strip() if title else None
+
+    if 'og:image' not in og:
+        # TODO: extract a favicon failing all else
+        meta_image = tree.xpath(
+            "//*/meta[translate(@itemprop, 'IMAGE', 'image')='image']/@content"
+        )
+        if meta_image:
+            og['og:image'] = _rebase_url(meta_image[0], media_uri)
+        else:
+            # TODO: consider inlined CSS styles as well as width & height attribs
+            images = tree.xpath("//img[@src][number(@width)>10][number(@height)>10]")
+            images = sorted(images, key=lambda i: (
+                -1 * float(i.attrib['width']) * float(i.attrib['height'])
+            ))
+            if not images:
+                images = tree.xpath("//img[@src]")
+            if images:
+                og['og:image'] = images[0].attrib['src']
+
+    if 'og:description' not in og:
+        meta_description = tree.xpath(
+            "//*/meta"
+            "[translate(@name, 'DESCRIPTION', 'description')='description']"
+            "/@content")
+        if meta_description:
+            og['og:description'] = meta_description[0]
+        else:
+            # grab any text nodes which are inside the <body/> tag...
+            # unless they are within an HTML5 semantic markup tag...
+            # <header/>, <nav/>, <aside/>, <footer/>
+            # ...or if they are within a <script/> or <style/> tag.
+            # This is a very very very coarse approximation to a plain text
+            # render of the page.
+
+            # We don't just use XPATH here as that is slow on some machines.
+
+            from lxml import etree
+
+            TAGS_TO_REMOVE = (
+                "header", "nav", "aside", "footer", "script", "style", etree.Comment
+            )
+
+            # Split all the text nodes into paragraphs (by splitting on new
+            # lines)
+            text_nodes = (
+                re.sub(r'\s+', '\n', el).strip()
+                for el in _iterate_over_text(tree.find("body"), *TAGS_TO_REMOVE)
+            )
+            og['og:description'] = summarize_paragraphs(text_nodes)
+
+    # TODO: delete the url downloads to stop diskfilling,
+    # as we only ever cared about its OG
+    return og
+
+
+def _iterate_over_text(tree, *tags_to_ignore):
+    """Iterate over the tree returning text nodes in a depth first fashion,
+    skipping text nodes inside certain tags.
+    """
+    # This is basically a stack that we extend using itertools.chain.
+    # This will either consist of an element to iterate over *or* a string
+    # to be returned.
+    elements = iter([tree])
+    while True:
+        el = elements.next()
+        if isinstance(el, basestring):
+            yield el
+        elif el.tag not in tags_to_ignore:
+            # el.text is the text before the first child, so we can immediately
+            # return it if the text exists.
+            if el.text:
+                yield el.text
+
+            # We add to the stack all the elements children, interspersed with
+            # each child's tail text (if it exists). The tail text of a node
+            # is text that comes *after* the node, so we always include it even
+            # if we ignore the child node.
+            elements = itertools.chain(
+                itertools.chain.from_iterable(  # Basically a flatmap
+                    [child, child.tail] if child.tail else [child]
+                    for child in el.iterchildren()
+                ),
+                elements
+            )
+
+
+def _rebase_url(url, base):
+    base = list(urlparse.urlparse(base))
+    url = list(urlparse.urlparse(url))
+    if not url[0]:  # fix up schema
+        url[0] = base[0] or "http"
+    if not url[1]:  # fix up hostname
+        url[1] = base[1]
+        if not url[2].startswith('/'):
+            url[2] = re.sub(r'/[^/]+$', '/', base[2]) + url[2]
+    return urlparse.urlunparse(url)
+
+
+def _is_media(content_type):
+    if content_type.lower().startswith("image/"):
+        return True
+
+
+def _is_html(content_type):
+    content_type = content_type.lower()
+    if (
+        content_type.startswith("text/html") or
+        content_type.startswith("application/xhtml")
+    ):
+        return True
 
 
 def summarize_paragraphs(text_nodes, min_size=200, max_size=500):
diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index b0923a9ca..0a2e78fd8 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -880,6 +880,7 @@ class SQLBaseStore(object):
             ctx = self._cache_id_gen.get_next()
             stream_id = ctx.__enter__()
             txn.call_after(ctx.__exit__, None, None, None)
+            txn.call_after(self.hs.get_notifier().on_new_replication_data)
 
             self._simple_insert_txn(
                 txn,
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index d2feee8db..ad026b5e0 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -600,7 +600,8 @@ class EventsStore(SQLBaseStore):
                 "rejections",
                 "redactions",
                 "room_memberships",
-                "state_events"
+                "state_events",
+                "topics"
             ):
                 txn.executemany(
                     "DELETE FROM %s WHERE event_id = ?" % (table,),
diff --git a/synapse/storage/registration.py b/synapse/storage/registration.py
index 7e7d32eb6..19cb3b31c 100644
--- a/synapse/storage/registration.py
+++ b/synapse/storage/registration.py
@@ -251,7 +251,7 @@ class RegistrationStore(background_updates.BackgroundUpdateStore):
         self.get_user_by_id.invalidate((user_id,))
 
     @defer.inlineCallbacks
-    def user_delete_access_tokens(self, user_id, except_token_ids=[],
+    def user_delete_access_tokens(self, user_id, except_token_id=None,
                                   device_id=None,
                                   delete_refresh_tokens=False):
         """
@@ -259,7 +259,7 @@ class RegistrationStore(background_updates.BackgroundUpdateStore):
 
         Args:
             user_id (str):  ID of user the tokens belong to
-            except_token_ids (list[str]): list of access_tokens which should
+            except_token_id (str): list of access_tokens IDs which should
                 *not* be deleted
             device_id (str|None):  ID of device the tokens are associated with.
                 If None, tokens associated with any device (or no device) will
@@ -269,53 +269,45 @@ class RegistrationStore(background_updates.BackgroundUpdateStore):
         Returns:
             defer.Deferred:
         """
-        def f(txn, table, except_tokens, call_after_delete):
-            sql = "SELECT token FROM %s WHERE user_id = ?" % table
-            clauses = [user_id]
-
+        def f(txn):
+            keyvalues = {
+                "user_id": user_id,
+            }
             if device_id is not None:
-                sql += " AND device_id = ?"
-                clauses.append(device_id)
+                keyvalues["device_id"] = device_id
 
-            if except_tokens:
-                sql += " AND id NOT IN (%s)" % (
-                    ",".join(["?" for _ in except_tokens]),
-                )
-                clauses += except_tokens
-
-            txn.execute(sql, clauses)
-
-            rows = txn.fetchall()
-
-            n = 100
-            chunks = [rows[i:i + n] for i in xrange(0, len(rows), n)]
-            for chunk in chunks:
-                if call_after_delete:
-                    for row in chunk:
-                        txn.call_after(call_after_delete, (row[0],))
-
-                txn.execute(
-                    "DELETE FROM %s WHERE token in (%s)" % (
-                        table,
-                        ",".join(["?" for _ in chunk]),
-                    ), [r[0] for r in chunk]
+            if delete_refresh_tokens:
+                self._simple_delete_txn(
+                    txn,
+                    table="refresh_tokens",
+                    keyvalues=keyvalues,
                 )
 
-        # delete refresh tokens first, to stop new access tokens being
-        # allocated while our backs are turned
-        if delete_refresh_tokens:
-            yield self.runInteraction(
-                "user_delete_access_tokens", f,
-                table="refresh_tokens",
-                except_tokens=[],
-                call_after_delete=None,
+            items = keyvalues.items()
+            where_clause = " AND ".join(k + " = ?" for k, _ in items)
+            values = [v for _, v in items]
+            if except_token_id:
+                where_clause += " AND id != ?"
+                values.append(except_token_id)
+
+            txn.execute(
+                "SELECT token FROM access_tokens WHERE %s" % where_clause,
+                values
+            )
+            rows = self.cursor_to_dict(txn)
+
+            for row in rows:
+                self._invalidate_cache_and_stream(
+                    txn, self.get_user_by_access_token, (row["token"],)
+                )
+
+            txn.execute(
+                "DELETE FROM access_tokens WHERE %s" % where_clause,
+                values
             )
 
         yield self.runInteraction(
             "user_delete_access_tokens", f,
-            table="access_tokens",
-            except_tokens=except_token_ids,
-            call_after_delete=self.get_user_by_access_token.invalidate,
         )
 
     def delete_access_token(self, access_token):
@@ -328,7 +320,9 @@ class RegistrationStore(background_updates.BackgroundUpdateStore):
                 },
             )
 
-            txn.call_after(self.get_user_by_access_token.invalidate, (access_token,))
+            self._invalidate_cache_and_stream(
+                txn, self.get_user_by_access_token, (access_token,)
+            )
 
         return self.runInteraction("delete_access_token", f)
 
diff --git a/tests/test_preview.py b/tests/test_preview.py
index 2a801173a..c8d6525a0 100644
--- a/tests/test_preview.py
+++ b/tests/test_preview.py
@@ -15,7 +15,9 @@
 
 from . import unittest
 
-from synapse.rest.media.v1.preview_url_resource import summarize_paragraphs
+from synapse.rest.media.v1.preview_url_resource import (
+    summarize_paragraphs, decode_and_calc_og
+)
 
 
 class PreviewTestCase(unittest.TestCase):
@@ -137,3 +139,79 @@ class PreviewTestCase(unittest.TestCase):
             " of old wooden houses in Northern Norway, the oldest house dating from"
             " 1789. The Arctic Cathedral, a modern church…"
         )
+
+
+class PreviewUrlTestCase(unittest.TestCase):
+    def test_simple(self):
+        html = """
+        <html>
+        <head><title>Foo</title></head>
+        <body>
+        Some text.
+        </body>
+        </html>
+        """
+
+        og = decode_and_calc_og(html, "http://example.com/test.html")
+
+        self.assertEquals(og, {
+            "og:title": "Foo",
+            "og:description": "Some text."
+        })
+
+    def test_comment(self):
+        html = """
+        <html>
+        <head><title>Foo</title></head>
+        <body>
+        <!-- HTML comment -->
+        Some text.
+        </body>
+        </html>
+        """
+
+        og = decode_and_calc_og(html, "http://example.com/test.html")
+
+        self.assertEquals(og, {
+            "og:title": "Foo",
+            "og:description": "Some text."
+        })
+
+    def test_comment2(self):
+        html = """
+        <html>
+        <head><title>Foo</title></head>
+        <body>
+        Some text.
+        <!-- HTML comment -->
+        Some more text.
+        <p>Text</p>
+        More text
+        </body>
+        </html>
+        """
+
+        og = decode_and_calc_og(html, "http://example.com/test.html")
+
+        self.assertEquals(og, {
+            "og:title": "Foo",
+            "og:description": "Some text.\n\nSome more text.\n\nText\n\nMore text"
+        })
+
+    def test_script(self):
+        html = """
+        <html>
+        <head><title>Foo</title></head>
+        <body>
+        <script> (function() {})() </script>
+        Some text.
+        </body>
+        </html>
+        """
+
+        og = decode_and_calc_og(html, "http://example.com/test.html")
+
+        self.assertEquals(og, {
+            "og:title": "Foo",
+            "og:description": "Some text."
+        })