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-rw-r--r--synapse/storage/_base.py56
-rw-r--r--synapse/storage/background_updates.py24
-rw-r--r--synapse/storage/client_ips.py253
-rw-r--r--synapse/storage/deviceinbox.py51
-rw-r--r--synapse/storage/devices.py63
-rw-r--r--synapse/storage/end_to_end_keys.py18
-rw-r--r--synapse/storage/engines/postgres.py20
-rw-r--r--synapse/storage/engines/sqlite.py14
-rw-r--r--synapse/storage/event_federation.py27
-rw-r--r--synapse/storage/events.py160
-rw-r--r--synapse/storage/events_bg_updates.py116
-rw-r--r--synapse/storage/events_worker.py42
-rw-r--r--synapse/storage/filtering.py4
-rw-r--r--synapse/storage/media_repository.py13
-rw-r--r--synapse/storage/monthly_active_users.py101
-rw-r--r--synapse/storage/presence.py14
-rw-r--r--synapse/storage/push_rule.py16
-rw-r--r--synapse/storage/pusher.py2
-rw-r--r--synapse/storage/receipts.py53
-rw-r--r--synapse/storage/registration.py265
-rw-r--r--synapse/storage/room.py246
-rw-r--r--synapse/storage/roommember.py325
-rw-r--r--synapse/storage/schema/delta/56/destinations_failure_ts.sql25
-rw-r--r--synapse/storage/schema/delta/56/destinations_retry_interval_type.sql.postgres18
-rw-r--r--synapse/storage/schema/delta/56/devices_last_seen.sql24
-rw-r--r--synapse/storage/schema/delta/56/public_room_list_idx.sql16
-rw-r--r--synapse/storage/schema/delta/56/redaction_censor.sql17
-rw-r--r--synapse/storage/schema/delta/56/redaction_censor2.sql20
-rw-r--r--synapse/storage/schema/delta/56/redaction_censor3_fix_update.sql.postgres25
-rw-r--r--synapse/storage/schema/delta/56/unique_user_filter_index.py52
-rw-r--r--synapse/storage/schema/delta/56/user_external_ids.sql24
-rw-r--r--synapse/storage/search.py68
-rw-r--r--synapse/storage/state.py396
-rw-r--r--synapse/storage/state_deltas.py38
-rw-r--r--synapse/storage/stats.py3
-rw-r--r--synapse/storage/transactions.py43
-rw-r--r--synapse/storage/user_directory.py178
-rw-r--r--synapse/storage/user_erasure_store.py18
38 files changed, 1945 insertions, 903 deletions
diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index abe16334ec..f5906fcd54 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -20,6 +20,7 @@ import random
 import sys
 import threading
 import time
+from typing import Iterable, Tuple
 
 from six import PY2, iteritems, iterkeys, itervalues
 from six.moves import builtins, intern, range
@@ -30,7 +31,7 @@ from prometheus_client import Histogram
 from twisted.internet import defer
 
 from synapse.api.errors import StoreError
-from synapse.logging.context import LoggingContext, PreserveLoggingContext
+from synapse.logging.context import LoggingContext, make_deferred_yieldable
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 from synapse.types import get_domain_from_id
@@ -550,8 +551,9 @@ class SQLBaseStore(object):
 
                 return func(conn, *args, **kwargs)
 
-        with PreserveLoggingContext():
-            result = yield self._db_pool.runWithConnection(inner_func, *args, **kwargs)
+        result = yield make_deferred_yieldable(
+            self._db_pool.runWithConnection(inner_func, *args, **kwargs)
+        )
 
         return result
 
@@ -1162,19 +1164,18 @@ class SQLBaseStore(object):
         if not iterable:
             return []
 
-        sql = "SELECT %s FROM %s" % (", ".join(retcols), table)
-
-        clauses = []
-        values = []
-        clauses.append("%s IN (%s)" % (column, ",".join("?" for _ in iterable)))
-        values.extend(iterable)
+        clause, values = make_in_list_sql_clause(txn.database_engine, column, iterable)
+        clauses = [clause]
 
         for key, value in iteritems(keyvalues):
             clauses.append("%s = ?" % (key,))
             values.append(value)
 
-        if clauses:
-            sql = "%s WHERE %s" % (sql, " AND ".join(clauses))
+        sql = "SELECT %s FROM %s WHERE %s" % (
+            ", ".join(retcols),
+            table,
+            " AND ".join(clauses),
+        )
 
         txn.execute(sql, values)
         return cls.cursor_to_dict(txn)
@@ -1323,10 +1324,8 @@ class SQLBaseStore(object):
 
         sql = "DELETE FROM %s" % table
 
-        clauses = []
-        values = []
-        clauses.append("%s IN (%s)" % (column, ",".join("?" for _ in iterable)))
-        values.extend(iterable)
+        clause, values = make_in_list_sql_clause(txn.database_engine, column, iterable)
+        clauses = [clause]
 
         for key, value in iteritems(keyvalues):
             clauses.append("%s = ?" % (key,))
@@ -1693,3 +1692,30 @@ def db_to_json(db_content):
     except Exception:
         logging.warning("Tried to decode '%r' as JSON and failed", db_content)
         raise
+
+
+def make_in_list_sql_clause(
+    database_engine, column: str, iterable: Iterable
+) -> Tuple[str, Iterable]:
+    """Returns an SQL clause that checks the given column is in the iterable.
+
+    On SQLite this expands to `column IN (?, ?, ...)`, whereas on Postgres
+    it expands to `column = ANY(?)`. While both DBs support the `IN` form,
+    using the `ANY` form on postgres means that it views queries with
+    different length iterables as the same, helping the query stats.
+
+    Args:
+        database_engine
+        column: Name of the column
+        iterable: The values to check the column against.
+
+    Returns:
+        A tuple of SQL query and the args
+    """
+
+    if database_engine.supports_using_any_list:
+        # This should hopefully be faster, but also makes postgres query
+        # stats easier to understand.
+        return "%s = ANY(?)" % (column,), [list(iterable)]
+    else:
+        return "%s IN (%s)" % (column, ",".join("?" for _ in iterable)), list(iterable)
diff --git a/synapse/storage/background_updates.py b/synapse/storage/background_updates.py
index e5f0668f09..80b57a948c 100644
--- a/synapse/storage/background_updates.py
+++ b/synapse/storage/background_updates.py
@@ -140,7 +140,7 @@ class BackgroundUpdateStore(SQLBaseStore):
             "background_updates",
             keyvalues=None,
             retcol="1",
-            desc="check_background_updates",
+            desc="has_completed_background_updates",
         )
         if not updates:
             self._all_done = True
@@ -148,6 +148,26 @@ class BackgroundUpdateStore(SQLBaseStore):
 
         return False
 
+    async def has_completed_background_update(self, update_name) -> bool:
+        """Check if the given background update has finished running.
+        """
+
+        if self._all_done:
+            return True
+
+        if update_name in self._background_update_queue:
+            return False
+
+        update_exists = await self._simple_select_one_onecol(
+            "background_updates",
+            keyvalues={"update_name": update_name},
+            retcol="1",
+            desc="has_completed_background_update",
+            allow_none=True,
+        )
+
+        return not update_exists
+
     @defer.inlineCallbacks
     def do_next_background_update(self, desired_duration_ms):
         """Does some amount of work on the next queued background update
@@ -218,7 +238,7 @@ class BackgroundUpdateStore(SQLBaseStore):
         duration_ms = time_stop - time_start
 
         logger.info(
-            "Updating %r. Updated %r items in %rms."
+            "Running background update %r. Processed %r items in %rms."
             " (total_rate=%r/ms, current_rate=%r/ms, total_updated=%r, batch_size=%r)",
             update_name,
             items_updated,
diff --git a/synapse/storage/client_ips.py b/synapse/storage/client_ips.py
index 6db8c54077..067820a5da 100644
--- a/synapse/storage/client_ips.py
+++ b/synapse/storage/client_ips.py
@@ -19,7 +19,7 @@ from six import iteritems
 
 from twisted.internet import defer
 
-from synapse.metrics.background_process_metrics import run_as_background_process
+from synapse.metrics.background_process_metrics import wrap_as_background_process
 from synapse.util.caches import CACHE_SIZE_FACTOR
 
 from . import background_updates
@@ -33,14 +33,9 @@ logger = logging.getLogger(__name__)
 LAST_SEEN_GRANULARITY = 120 * 1000
 
 
-class ClientIpStore(background_updates.BackgroundUpdateStore):
+class ClientIpBackgroundUpdateStore(background_updates.BackgroundUpdateStore):
     def __init__(self, db_conn, hs):
-
-        self.client_ip_last_seen = Cache(
-            name="client_ip_last_seen", keylen=4, max_entries=50000 * CACHE_SIZE_FACTOR
-        )
-
-        super(ClientIpStore, self).__init__(db_conn, hs)
+        super(ClientIpBackgroundUpdateStore, self).__init__(db_conn, hs)
 
         self.register_background_index_update(
             "user_ips_device_index",
@@ -85,14 +80,9 @@ class ClientIpStore(background_updates.BackgroundUpdateStore):
             "user_ips_drop_nonunique_index", self._remove_user_ip_nonunique
         )
 
-        # (user_id, access_token, ip,) -> (user_agent, device_id, last_seen)
-        self._batch_row_update = {}
-
-        self._client_ip_looper = self._clock.looping_call(
-            self._update_client_ips_batch, 5 * 1000
-        )
-        self.hs.get_reactor().addSystemEventTrigger(
-            "before", "shutdown", self._update_client_ips_batch
+        # Update the last seen info in devices.
+        self.register_background_update_handler(
+            "devices_last_seen", self._devices_last_seen_update
         )
 
     @defer.inlineCallbacks
@@ -294,6 +284,110 @@ class ClientIpStore(background_updates.BackgroundUpdateStore):
         return batch_size
 
     @defer.inlineCallbacks
+    def _devices_last_seen_update(self, progress, batch_size):
+        """Background update to insert last seen info into devices table
+        """
+
+        last_user_id = progress.get("last_user_id", "")
+        last_device_id = progress.get("last_device_id", "")
+
+        def _devices_last_seen_update_txn(txn):
+            # This consists of two queries:
+            #
+            #   1. The sub-query searches for the next N devices and joins
+            #      against user_ips to find the max last_seen associated with
+            #      that device.
+            #   2. The outer query then joins again against user_ips on
+            #      user/device/last_seen. This *should* hopefully only
+            #      return one row, but if it does return more than one then
+            #      we'll just end up updating the same device row multiple
+            #      times, which is fine.
+
+            if self.database_engine.supports_tuple_comparison:
+                where_clause = "(user_id, device_id) > (?, ?)"
+                where_args = [last_user_id, last_device_id]
+            else:
+                # We explicitly do a `user_id >= ? AND (...)` here to ensure
+                # that an index is used, as doing `user_id > ? OR (user_id = ? AND ...)`
+                # makes it hard for query optimiser to tell that it can use the
+                # index on user_id
+                where_clause = "user_id >= ? AND (user_id > ? OR device_id > ?)"
+                where_args = [last_user_id, last_user_id, last_device_id]
+
+            sql = """
+                SELECT
+                    last_seen, ip, user_agent, user_id, device_id
+                FROM (
+                    SELECT
+                        user_id, device_id, MAX(u.last_seen) AS last_seen
+                    FROM devices
+                    INNER JOIN user_ips AS u USING (user_id, device_id)
+                    WHERE %(where_clause)s
+                    GROUP BY user_id, device_id
+                    ORDER BY user_id ASC, device_id ASC
+                    LIMIT ?
+                ) c
+                INNER JOIN user_ips AS u USING (user_id, device_id, last_seen)
+            """ % {
+                "where_clause": where_clause
+            }
+            txn.execute(sql, where_args + [batch_size])
+
+            rows = txn.fetchall()
+            if not rows:
+                return 0
+
+            sql = """
+                UPDATE devices
+                SET last_seen = ?, ip = ?, user_agent = ?
+                WHERE user_id = ? AND device_id = ?
+            """
+            txn.execute_batch(sql, rows)
+
+            _, _, _, user_id, device_id = rows[-1]
+            self._background_update_progress_txn(
+                txn,
+                "devices_last_seen",
+                {"last_user_id": user_id, "last_device_id": device_id},
+            )
+
+            return len(rows)
+
+        updated = yield self.runInteraction(
+            "_devices_last_seen_update", _devices_last_seen_update_txn
+        )
+
+        if not updated:
+            yield self._end_background_update("devices_last_seen")
+
+        return updated
+
+
+class ClientIpStore(ClientIpBackgroundUpdateStore):
+    def __init__(self, db_conn, hs):
+
+        self.client_ip_last_seen = Cache(
+            name="client_ip_last_seen", keylen=4, max_entries=50000 * CACHE_SIZE_FACTOR
+        )
+
+        super(ClientIpStore, self).__init__(db_conn, hs)
+
+        self.user_ips_max_age = hs.config.user_ips_max_age
+
+        # (user_id, access_token, ip,) -> (user_agent, device_id, last_seen)
+        self._batch_row_update = {}
+
+        self._client_ip_looper = self._clock.looping_call(
+            self._update_client_ips_batch, 5 * 1000
+        )
+        self.hs.get_reactor().addSystemEventTrigger(
+            "before", "shutdown", self._update_client_ips_batch
+        )
+
+        if self.user_ips_max_age:
+            self._clock.looping_call(self._prune_old_user_ips, 5 * 1000)
+
+    @defer.inlineCallbacks
     def insert_client_ip(
         self, user_id, access_token, ip, user_agent, device_id, now=None
     ):
@@ -314,20 +408,19 @@ class ClientIpStore(background_updates.BackgroundUpdateStore):
 
         self._batch_row_update[key] = (user_agent, device_id, now)
 
+    @wrap_as_background_process("update_client_ips")
     def _update_client_ips_batch(self):
 
         # If the DB pool has already terminated, don't try updating
         if not self.hs.get_db_pool().running:
             return
 
-        def update():
-            to_update = self._batch_row_update
-            self._batch_row_update = {}
-            return self.runInteraction(
-                "_update_client_ips_batch", self._update_client_ips_batch_txn, to_update
-            )
+        to_update = self._batch_row_update
+        self._batch_row_update = {}
 
-        return run_as_background_process("update_client_ips", update)
+        return self.runInteraction(
+            "_update_client_ips_batch", self._update_client_ips_batch_txn, to_update
+        )
 
     def _update_client_ips_batch_txn(self, txn, to_update):
         if "user_ips" in self._unsafe_to_upsert_tables or (
@@ -354,6 +447,21 @@ class ClientIpStore(background_updates.BackgroundUpdateStore):
                     },
                     lock=False,
                 )
+
+                # Technically an access token might not be associated with
+                # a device so we need to check.
+                if device_id:
+                    self._simple_upsert_txn(
+                        txn,
+                        table="devices",
+                        keyvalues={"user_id": user_id, "device_id": device_id},
+                        values={
+                            "user_agent": user_agent,
+                            "last_seen": last_seen,
+                            "ip": ip,
+                        },
+                        lock=False,
+                    )
             except Exception as e:
                 # Failed to upsert, log and continue
                 logger.error("Failed to insert client IP %r: %r", entry, e)
@@ -372,19 +480,14 @@ class ClientIpStore(background_updates.BackgroundUpdateStore):
             keys giving the column names
         """
 
-        res = yield self.runInteraction(
-            "get_last_client_ip_by_device",
-            self._get_last_client_ip_by_device_txn,
-            user_id,
-            device_id,
-            retcols=(
-                "user_id",
-                "access_token",
-                "ip",
-                "user_agent",
-                "device_id",
-                "last_seen",
-            ),
+        keyvalues = {"user_id": user_id}
+        if device_id is not None:
+            keyvalues["device_id"] = device_id
+
+        res = yield self._simple_select_list(
+            table="devices",
+            keyvalues=keyvalues,
+            retcols=("user_id", "ip", "user_agent", "device_id", "last_seen"),
         )
 
         ret = {(d["user_id"], d["device_id"]): d for d in res}
@@ -403,42 +506,6 @@ class ClientIpStore(background_updates.BackgroundUpdateStore):
                     }
         return ret
 
-    @classmethod
-    def _get_last_client_ip_by_device_txn(cls, txn, user_id, device_id, retcols):
-        where_clauses = []
-        bindings = []
-        if device_id is None:
-            where_clauses.append("user_id = ?")
-            bindings.extend((user_id,))
-        else:
-            where_clauses.append("(user_id = ? AND device_id = ?)")
-            bindings.extend((user_id, device_id))
-
-        if not where_clauses:
-            return []
-
-        inner_select = (
-            "SELECT MAX(last_seen) mls, user_id, device_id FROM user_ips "
-            "WHERE %(where)s "
-            "GROUP BY user_id, device_id"
-        ) % {"where": " OR ".join(where_clauses)}
-
-        sql = (
-            "SELECT %(retcols)s FROM user_ips "
-            "JOIN (%(inner_select)s) ips ON"
-            "    user_ips.last_seen = ips.mls AND"
-            "    user_ips.user_id = ips.user_id AND"
-            "    (user_ips.device_id = ips.device_id OR"
-            "         (user_ips.device_id IS NULL AND ips.device_id IS NULL)"
-            "    )"
-        ) % {
-            "retcols": ",".join("user_ips." + c for c in retcols),
-            "inner_select": inner_select,
-        }
-
-        txn.execute(sql, bindings)
-        return cls.cursor_to_dict(txn)
-
     @defer.inlineCallbacks
     def get_user_ip_and_agents(self, user):
         user_id = user.to_string()
@@ -470,3 +537,45 @@ class ClientIpStore(background_updates.BackgroundUpdateStore):
             }
             for (access_token, ip), (user_agent, last_seen) in iteritems(results)
         )
+
+    @wrap_as_background_process("prune_old_user_ips")
+    async def _prune_old_user_ips(self):
+        """Removes entries in user IPs older than the configured period.
+        """
+
+        if self.user_ips_max_age is None:
+            # Nothing to do
+            return
+
+        if not await self.has_completed_background_update("devices_last_seen"):
+            # Only start pruning if we have finished populating the devices
+            # last seen info.
+            return
+
+        # We do a slightly funky SQL delete to ensure we don't try and delete
+        # too much at once (as the table may be very large from before we
+        # started pruning).
+        #
+        # This works by finding the max last_seen that is less than the given
+        # time, but has no more than N rows before it, deleting all rows with
+        # a lesser last_seen time. (We COALESCE so that the sub-SELECT always
+        # returns exactly one row).
+        sql = """
+            DELETE FROM user_ips
+            WHERE last_seen <= (
+                SELECT COALESCE(MAX(last_seen), -1)
+                FROM (
+                    SELECT last_seen FROM user_ips
+                    WHERE last_seen <= ?
+                    ORDER BY last_seen ASC
+                    LIMIT 5000
+                ) AS u
+            )
+        """
+
+        timestamp = self.clock.time_msec() - self.user_ips_max_age
+
+        def _prune_old_user_ips_txn(txn):
+            txn.execute(sql, (timestamp,))
+
+        await self.runInteraction("_prune_old_user_ips", _prune_old_user_ips_txn)
diff --git a/synapse/storage/deviceinbox.py b/synapse/storage/deviceinbox.py
index 6b7458304e..f04aad0743 100644
--- a/synapse/storage/deviceinbox.py
+++ b/synapse/storage/deviceinbox.py
@@ -20,7 +20,7 @@ from canonicaljson import json
 from twisted.internet import defer
 
 from synapse.logging.opentracing import log_kv, set_tag, trace
-from synapse.storage._base import SQLBaseStore
+from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
 from synapse.storage.background_updates import BackgroundUpdateStore
 from synapse.util.caches.expiringcache import ExpiringCache
 
@@ -208,11 +208,11 @@ class DeviceInboxWorkerStore(SQLBaseStore):
         )
 
 
-class DeviceInboxStore(DeviceInboxWorkerStore, BackgroundUpdateStore):
+class DeviceInboxBackgroundUpdateStore(BackgroundUpdateStore):
     DEVICE_INBOX_STREAM_ID = "device_inbox_stream_drop"
 
     def __init__(self, db_conn, hs):
-        super(DeviceInboxStore, self).__init__(db_conn, hs)
+        super(DeviceInboxBackgroundUpdateStore, self).__init__(db_conn, hs)
 
         self.register_background_index_update(
             "device_inbox_stream_index",
@@ -225,6 +225,26 @@ class DeviceInboxStore(DeviceInboxWorkerStore, BackgroundUpdateStore):
             self.DEVICE_INBOX_STREAM_ID, self._background_drop_index_device_inbox
         )
 
+    @defer.inlineCallbacks
+    def _background_drop_index_device_inbox(self, progress, batch_size):
+        def reindex_txn(conn):
+            txn = conn.cursor()
+            txn.execute("DROP INDEX IF EXISTS device_inbox_stream_id")
+            txn.close()
+
+        yield self.runWithConnection(reindex_txn)
+
+        yield self._end_background_update(self.DEVICE_INBOX_STREAM_ID)
+
+        return 1
+
+
+class DeviceInboxStore(DeviceInboxWorkerStore, DeviceInboxBackgroundUpdateStore):
+    DEVICE_INBOX_STREAM_ID = "device_inbox_stream_drop"
+
+    def __init__(self, db_conn, hs):
+        super(DeviceInboxStore, self).__init__(db_conn, hs)
+
         # Map of (user_id, device_id) to the last stream_id that has been
         # deleted up to. This is so that we can no op deletions.
         self._last_device_delete_cache = ExpiringCache(
@@ -358,15 +378,15 @@ class DeviceInboxStore(DeviceInboxWorkerStore, BackgroundUpdateStore):
             else:
                 if not devices:
                     continue
-                sql = (
-                    "SELECT device_id FROM devices"
-                    " WHERE user_id = ? AND device_id IN ("
-                    + ",".join("?" * len(devices))
-                    + ")"
+
+                clause, args = make_in_list_sql_clause(
+                    txn.database_engine, "device_id", devices
                 )
+                sql = "SELECT device_id FROM devices WHERE user_id = ? AND " + clause
+
                 # TODO: Maybe this needs to be done in batches if there are
                 # too many local devices for a given user.
-                txn.execute(sql, [user_id] + devices)
+                txn.execute(sql, [user_id] + list(args))
                 for row in txn:
                     # Only insert into the local inbox if the device exists on
                     # this server
@@ -435,16 +455,3 @@ class DeviceInboxStore(DeviceInboxWorkerStore, BackgroundUpdateStore):
         return self.runInteraction(
             "get_all_new_device_messages", get_all_new_device_messages_txn
         )
-
-    @defer.inlineCallbacks
-    def _background_drop_index_device_inbox(self, progress, batch_size):
-        def reindex_txn(conn):
-            txn = conn.cursor()
-            txn.execute("DROP INDEX IF EXISTS device_inbox_stream_id")
-            txn.close()
-
-        yield self.runWithConnection(reindex_txn)
-
-        yield self._end_background_update(self.DEVICE_INBOX_STREAM_ID)
-
-        return 1
diff --git a/synapse/storage/devices.py b/synapse/storage/devices.py
index 2db3ef4004..f7a3542348 100644
--- a/synapse/storage/devices.py
+++ b/synapse/storage/devices.py
@@ -30,7 +30,12 @@ from synapse.logging.opentracing import (
     whitelisted_homeserver,
 )
 from synapse.metrics.background_process_metrics import run_as_background_process
-from synapse.storage._base import Cache, SQLBaseStore, db_to_json
+from synapse.storage._base import (
+    Cache,
+    SQLBaseStore,
+    db_to_json,
+    make_in_list_sql_clause,
+)
 from synapse.storage.background_updates import BackgroundUpdateStore
 from synapse.util import batch_iter
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks, cachedList
@@ -487,11 +492,14 @@ class DeviceWorkerStore(SQLBaseStore):
             sql = """
                 SELECT DISTINCT user_id FROM device_lists_stream
                 WHERE stream_id > ?
-                AND user_id IN (%s)
+                AND
             """
 
             for chunk in batch_iter(to_check, 100):
-                txn.execute(sql % (",".join("?" for _ in chunk),), (from_key,) + chunk)
+                clause, args = make_in_list_sql_clause(
+                    txn.database_engine, "user_id", chunk
+                )
+                txn.execute(sql + clause, (from_key,) + tuple(args))
                 changes.update(user_id for user_id, in txn)
 
             return changes
@@ -573,17 +581,9 @@ class DeviceWorkerStore(SQLBaseStore):
         return results
 
 
-class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
+class DeviceBackgroundUpdateStore(BackgroundUpdateStore):
     def __init__(self, db_conn, hs):
-        super(DeviceStore, self).__init__(db_conn, hs)
-
-        # Map of (user_id, device_id) -> bool. If there is an entry that implies
-        # the device exists.
-        self.device_id_exists_cache = Cache(
-            name="device_id_exists", keylen=2, max_entries=10000
-        )
-
-        self._clock.looping_call(self._prune_old_outbound_device_pokes, 60 * 60 * 1000)
+        super(DeviceBackgroundUpdateStore, self).__init__(db_conn, hs)
 
         self.register_background_index_update(
             "device_lists_stream_idx",
@@ -617,6 +617,31 @@ class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
         )
 
     @defer.inlineCallbacks
+    def _drop_device_list_streams_non_unique_indexes(self, progress, batch_size):
+        def f(conn):
+            txn = conn.cursor()
+            txn.execute("DROP INDEX IF EXISTS device_lists_remote_cache_id")
+            txn.execute("DROP INDEX IF EXISTS device_lists_remote_extremeties_id")
+            txn.close()
+
+        yield self.runWithConnection(f)
+        yield self._end_background_update(DROP_DEVICE_LIST_STREAMS_NON_UNIQUE_INDEXES)
+        return 1
+
+
+class DeviceStore(DeviceWorkerStore, DeviceBackgroundUpdateStore):
+    def __init__(self, db_conn, hs):
+        super(DeviceStore, self).__init__(db_conn, hs)
+
+        # Map of (user_id, device_id) -> bool. If there is an entry that implies
+        # the device exists.
+        self.device_id_exists_cache = Cache(
+            name="device_id_exists", keylen=2, max_entries=10000
+        )
+
+        self._clock.looping_call(self._prune_old_outbound_device_pokes, 60 * 60 * 1000)
+
+    @defer.inlineCallbacks
     def store_device(self, user_id, device_id, initial_device_display_name):
         """Ensure the given device is known; add it to the store if not
 
@@ -987,15 +1012,3 @@ class DeviceStore(DeviceWorkerStore, BackgroundUpdateStore):
             "_prune_old_outbound_device_pokes",
             _prune_txn,
         )
-
-    @defer.inlineCallbacks
-    def _drop_device_list_streams_non_unique_indexes(self, progress, batch_size):
-        def f(conn):
-            txn = conn.cursor()
-            txn.execute("DROP INDEX IF EXISTS device_lists_remote_cache_id")
-            txn.execute("DROP INDEX IF EXISTS device_lists_remote_extremeties_id")
-            txn.close()
-
-        yield self.runWithConnection(f)
-        yield self._end_background_update(DROP_DEVICE_LIST_STREAMS_NON_UNIQUE_INDEXES)
-        return 1
diff --git a/synapse/storage/end_to_end_keys.py b/synapse/storage/end_to_end_keys.py
index 3c82f789fa..ebcd1c9ea2 100644
--- a/synapse/storage/end_to_end_keys.py
+++ b/synapse/storage/end_to_end_keys.py
@@ -42,7 +42,8 @@ class EndToEndKeyWorkerStore(SQLBaseStore):
                 This option only takes effect if include_all_devices is true.
         Returns:
             Dict mapping from user-id to dict mapping from device_id to
-            dict containing "key_json", "device_display_name".
+            key data.  The key data will be a dict in the same format as the
+            DeviceKeys type returned by POST /_matrix/client/r0/keys/query.
         """
         set_tag("query_list", query_list)
         if not query_list:
@@ -56,11 +57,20 @@ class EndToEndKeyWorkerStore(SQLBaseStore):
             include_deleted_devices,
         )
 
+        # Build the result structure, un-jsonify the results, and add the
+        # "unsigned" section
+        rv = {}
         for user_id, device_keys in iteritems(results):
+            rv[user_id] = {}
             for device_id, device_info in iteritems(device_keys):
-                device_info["keys"] = db_to_json(device_info.pop("key_json"))
-
-        return results
+                r = db_to_json(device_info.pop("key_json"))
+                r["unsigned"] = {}
+                display_name = device_info["device_display_name"]
+                if display_name is not None:
+                    r["unsigned"]["device_display_name"] = display_name
+                rv[user_id][device_id] = r
+
+        return rv
 
     @trace
     def _get_e2e_device_keys_txn(
diff --git a/synapse/storage/engines/postgres.py b/synapse/storage/engines/postgres.py
index 289b6bc281..b7c4eda338 100644
--- a/synapse/storage/engines/postgres.py
+++ b/synapse/storage/engines/postgres.py
@@ -22,6 +22,13 @@ class PostgresEngine(object):
     def __init__(self, database_module, database_config):
         self.module = database_module
         self.module.extensions.register_type(self.module.extensions.UNICODE)
+
+        # Disables passing `bytes` to txn.execute, c.f. #6186. If you do
+        # actually want to use bytes than wrap it in `bytearray`.
+        def _disable_bytes_adapter(_):
+            raise Exception("Passing bytes to DB is disabled.")
+
+        self.module.extensions.register_adapter(bytes, _disable_bytes_adapter)
         self.synchronous_commit = database_config.get("synchronous_commit", True)
         self._version = None  # unknown as yet
 
@@ -72,6 +79,19 @@ class PostgresEngine(object):
         """
         return True
 
+    @property
+    def supports_tuple_comparison(self):
+        """
+        Do we support comparing tuples, i.e. `(a, b) > (c, d)`?
+        """
+        return True
+
+    @property
+    def supports_using_any_list(self):
+        """Do we support using `a = ANY(?)` and passing a list
+        """
+        return True
+
     def is_deadlock(self, error):
         if isinstance(error, self.module.DatabaseError):
             # https://www.postgresql.org/docs/current/static/errcodes-appendix.html
diff --git a/synapse/storage/engines/sqlite.py b/synapse/storage/engines/sqlite.py
index e9b9caa49a..ddad17dc5a 100644
--- a/synapse/storage/engines/sqlite.py
+++ b/synapse/storage/engines/sqlite.py
@@ -38,6 +38,20 @@ class Sqlite3Engine(object):
         """
         return self.module.sqlite_version_info >= (3, 24, 0)
 
+    @property
+    def supports_tuple_comparison(self):
+        """
+        Do we support comparing tuples, i.e. `(a, b) > (c, d)`? This requires
+        SQLite 3.15+.
+        """
+        return self.module.sqlite_version_info >= (3, 15, 0)
+
+    @property
+    def supports_using_any_list(self):
+        """Do we support using `a = ANY(?)` and passing a list
+        """
+        return False
+
     def check_database(self, txn):
         pass
 
diff --git a/synapse/storage/event_federation.py b/synapse/storage/event_federation.py
index 4f500d893e..47cc10d32a 100644
--- a/synapse/storage/event_federation.py
+++ b/synapse/storage/event_federation.py
@@ -12,6 +12,7 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import itertools
 import logging
 import random
 
@@ -24,7 +25,7 @@ from twisted.internet import defer
 
 from synapse.api.errors import StoreError
 from synapse.metrics.background_process_metrics import run_as_background_process
-from synapse.storage._base import SQLBaseStore
+from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
 from synapse.storage.events_worker import EventsWorkerStore
 from synapse.storage.signatures import SignatureWorkerStore
 from synapse.util.caches.descriptors import cached
@@ -67,7 +68,7 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
         else:
             results = set()
 
-        base_sql = "SELECT auth_id FROM event_auth WHERE event_id IN (%s)"
+        base_sql = "SELECT auth_id FROM event_auth WHERE "
 
         front = set(event_ids)
         while front:
@@ -75,7 +76,10 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
             front_list = list(front)
             chunks = [front_list[x : x + 100] for x in range(0, len(front), 100)]
             for chunk in chunks:
-                txn.execute(base_sql % (",".join(["?"] * len(chunk)),), chunk)
+                clause, args = make_in_list_sql_clause(
+                    txn.database_engine, "event_id", chunk
+                )
+                txn.execute(base_sql + clause, list(args))
                 new_front.update([r[0] for r in txn])
 
             new_front -= results
@@ -190,12 +194,13 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
             room_id,
         )
 
-    def get_rooms_with_many_extremities(self, min_count, limit):
+    def get_rooms_with_many_extremities(self, min_count, limit, room_id_filter):
         """Get the top rooms with at least N extremities.
 
         Args:
             min_count (int): The minimum number of extremities
             limit (int): The maximum number of rooms to return.
+            room_id_filter (iterable[str]): room_ids to exclude from the results
 
         Returns:
             Deferred[list]: At most `limit` room IDs that have at least
@@ -203,15 +208,25 @@ class EventFederationWorkerStore(EventsWorkerStore, SignatureWorkerStore, SQLBas
         """
 
         def _get_rooms_with_many_extremities_txn(txn):
+            where_clause = "1=1"
+            if room_id_filter:
+                where_clause = "room_id NOT IN (%s)" % (
+                    ",".join("?" for _ in room_id_filter),
+                )
+
             sql = """
                 SELECT room_id FROM event_forward_extremities
+                WHERE %s
                 GROUP BY room_id
                 HAVING count(*) > ?
                 ORDER BY count(*) DESC
                 LIMIT ?
-            """
+            """ % (
+                where_clause,
+            )
 
-            txn.execute(sql, (min_count, limit))
+            query_args = list(itertools.chain(room_id_filter, [min_count, limit]))
+            txn.execute(sql, query_args)
             return [room_id for room_id, in txn]
 
         return self.runInteraction(
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index 1958afe1d7..ee49ef235d 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -33,11 +33,13 @@ from synapse.api.constants import EventTypes
 from synapse.api.errors import SynapseError
 from synapse.events import EventBase  # noqa: F401
 from synapse.events.snapshot import EventContext  # noqa: F401
+from synapse.events.utils import prune_event_dict
 from synapse.logging.context import PreserveLoggingContext, make_deferred_yieldable
 from synapse.logging.utils import log_function
 from synapse.metrics import BucketCollector
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.state import StateResolutionStore
+from synapse.storage._base import make_in_list_sql_clause
 from synapse.storage.background_updates import BackgroundUpdateStore
 from synapse.storage.event_federation import EventFederationStore
 from synapse.storage.events_worker import EventsWorkerStore
@@ -262,6 +264,14 @@ class EventsStore(
 
         hs.get_clock().looping_call(read_forward_extremities, 60 * 60 * 1000)
 
+        def _censor_redactions():
+            return run_as_background_process(
+                "_censor_redactions", self._censor_redactions
+            )
+
+        if self.hs.config.redaction_retention_period is not None:
+            hs.get_clock().looping_call(_censor_redactions, 5 * 60 * 1000)
+
     @defer.inlineCallbacks
     def _read_forward_extremities(self):
         def fetch(txn):
@@ -632,14 +642,16 @@ class EventsStore(
                 LEFT JOIN rejections USING (event_id)
                 LEFT JOIN event_json USING (event_id)
             WHERE
-                prev_event_id IN (%s)
-                AND NOT events.outlier
+                NOT events.outlier
                 AND rejections.event_id IS NULL
-            """ % (
-                ",".join("?" for _ in batch),
+                AND
+            """
+
+            clause, args = make_in_list_sql_clause(
+                self.database_engine, "prev_event_id", batch
             )
 
-            txn.execute(sql, batch)
+            txn.execute(sql + clause, args)
             results.extend(r[0] for r in txn if not json.loads(r[1]).get("soft_failed"))
 
         for chunk in batch_iter(event_ids, 100):
@@ -686,13 +698,15 @@ class EventsStore(
                     LEFT JOIN rejections USING (event_id)
                     LEFT JOIN event_json USING (event_id)
                 WHERE
-                    event_id IN (%s)
-                    AND NOT events.outlier
-                """ % (
-                    ",".join("?" for _ in to_recursively_check),
+                    NOT events.outlier
+                    AND
+                """
+
+                clause, args = make_in_list_sql_clause(
+                    self.database_engine, "event_id", to_recursively_check
                 )
 
-                txn.execute(sql, to_recursively_check)
+                txn.execute(sql + clause, args)
                 to_recursively_check = []
 
                 for event_id, prev_event_id, metadata, rejected in txn:
@@ -1380,6 +1394,18 @@ class EventsStore(
             ],
         )
 
+        for event, _ in events_and_contexts:
+            if not event.internal_metadata.is_redacted():
+                # If we're persisting an unredacted event we go and ensure
+                # that we mark any redactions that reference this event as
+                # requiring censoring.
+                self._simple_update_txn(
+                    txn,
+                    table="redactions",
+                    keyvalues={"redacts": event.event_id},
+                    updatevalues={"have_censored": False},
+                )
+
     def _store_rejected_events_txn(self, txn, events_and_contexts):
         """Add rows to the 'rejections' table for received events which were
         rejected
@@ -1522,10 +1548,14 @@ class EventsStore(
                 " FROM events as e"
                 " LEFT JOIN rejections as rej USING (event_id)"
                 " LEFT JOIN redactions as r ON e.event_id = r.redacts"
-                " WHERE e.event_id IN (%s)"
-            ) % (",".join(["?"] * len(ev_map)),)
+                " WHERE "
+            )
+
+            clause, args = make_in_list_sql_clause(
+                self.database_engine, "e.event_id", list(ev_map)
+            )
 
-            txn.execute(sql, list(ev_map))
+            txn.execute(sql + clause, args)
             rows = self.cursor_to_dict(txn)
             for row in rows:
                 event = ev_map[row["event_id"]]
@@ -1543,12 +1573,101 @@ class EventsStore(
     def _store_redaction(self, txn, event):
         # invalidate the cache for the redacted event
         txn.call_after(self._invalidate_get_event_cache, event.redacts)
-        txn.execute(
-            "INSERT INTO redactions (event_id, redacts) VALUES (?,?)",
-            (event.event_id, event.redacts),
+
+        self._simple_insert_txn(
+            txn,
+            table="redactions",
+            values={
+                "event_id": event.event_id,
+                "redacts": event.redacts,
+                "received_ts": self._clock.time_msec(),
+            },
         )
 
     @defer.inlineCallbacks
+    def _censor_redactions(self):
+        """Censors all redactions older than the configured period that haven't
+        been censored yet.
+
+        By censor we mean update the event_json table with the redacted event.
+
+        Returns:
+            Deferred
+        """
+
+        if self.hs.config.redaction_retention_period is None:
+            return
+
+        before_ts = self._clock.time_msec() - self.hs.config.redaction_retention_period
+
+        # We fetch all redactions that:
+        #   1. point to an event we have,
+        #   2. has a received_ts from before the cut off, and
+        #   3. we haven't yet censored.
+        #
+        # This is limited to 100 events to ensure that we don't try and do too
+        # much at once. We'll get called again so this should eventually catch
+        # up.
+        sql = """
+            SELECT redactions.event_id, redacts FROM redactions
+            LEFT JOIN events AS original_event ON (
+                redacts = original_event.event_id
+            )
+            WHERE NOT have_censored
+            AND redactions.received_ts <= ?
+            ORDER BY redactions.received_ts ASC
+            LIMIT ?
+        """
+
+        rows = yield self._execute(
+            "_censor_redactions_fetch", None, sql, before_ts, 100
+        )
+
+        updates = []
+
+        for redaction_id, event_id in rows:
+            redaction_event = yield self.get_event(redaction_id, allow_none=True)
+            original_event = yield self.get_event(
+                event_id, allow_rejected=True, allow_none=True
+            )
+
+            # The SQL above ensures that we have both the redaction and
+            # original event, so if the `get_event` calls return None it
+            # means that the redaction wasn't allowed. Either way we know that
+            # the result won't change so we mark the fact that we've checked.
+            if (
+                redaction_event
+                and original_event
+                and original_event.internal_metadata.is_redacted()
+            ):
+                # Redaction was allowed
+                pruned_json = encode_json(prune_event_dict(original_event.get_dict()))
+            else:
+                # Redaction wasn't allowed
+                pruned_json = None
+
+            updates.append((redaction_id, event_id, pruned_json))
+
+        def _update_censor_txn(txn):
+            for redaction_id, event_id, pruned_json in updates:
+                if pruned_json:
+                    self._simple_update_one_txn(
+                        txn,
+                        table="event_json",
+                        keyvalues={"event_id": event_id},
+                        updatevalues={"json": pruned_json},
+                    )
+
+                self._simple_update_one_txn(
+                    txn,
+                    table="redactions",
+                    keyvalues={"event_id": redaction_id},
+                    updatevalues={"have_censored": True},
+                )
+
+        yield self.runInteraction("_update_censor_txn", _update_censor_txn)
+
+    @defer.inlineCallbacks
     def count_daily_messages(self):
         """
         Returns an estimate of the number of messages sent in the last day.
@@ -2139,11 +2258,12 @@ class EventsStore(
             sql = """
                 SELECT DISTINCT state_group FROM event_to_state_groups
                 LEFT JOIN events_to_purge AS ep USING (event_id)
-                WHERE state_group IN (%s) AND ep.event_id IS NULL
-            """ % (
-                ",".join("?" for _ in current_search),
+                WHERE ep.event_id IS NULL AND
+            """
+            clause, args = make_in_list_sql_clause(
+                txn.database_engine, "state_group", current_search
             )
-            txn.execute(sql, list(current_search))
+            txn.execute(sql + clause, list(args))
 
             referenced = set(sg for sg, in txn)
             referenced_groups |= referenced
diff --git a/synapse/storage/events_bg_updates.py b/synapse/storage/events_bg_updates.py
index 6587f31e2b..31ea6f917f 100644
--- a/synapse/storage/events_bg_updates.py
+++ b/synapse/storage/events_bg_updates.py
@@ -21,6 +21,7 @@ from canonicaljson import json
 
 from twisted.internet import defer
 
+from synapse.storage._base import make_in_list_sql_clause
 from synapse.storage.background_updates import BackgroundUpdateStore
 
 logger = logging.getLogger(__name__)
@@ -67,6 +68,23 @@ class EventsBackgroundUpdatesStore(BackgroundUpdateStore):
             self.DELETE_SOFT_FAILED_EXTREMITIES, self._cleanup_extremities_bg_update
         )
 
+        self.register_background_update_handler(
+            "redactions_received_ts", self._redactions_received_ts
+        )
+
+        # This index gets deleted in `event_fix_redactions_bytes` update
+        self.register_background_index_update(
+            "event_fix_redactions_bytes_create_index",
+            index_name="redactions_censored_redacts",
+            table="redactions",
+            columns=["redacts"],
+            where_clause="have_censored",
+        )
+
+        self.register_background_update_handler(
+            "event_fix_redactions_bytes", self._event_fix_redactions_bytes
+        )
+
     @defer.inlineCallbacks
     def _background_reindex_fields_sender(self, progress, batch_size):
         target_min_stream_id = progress["target_min_stream_id_inclusive"]
@@ -308,12 +326,13 @@ class EventsBackgroundUpdatesStore(BackgroundUpdateStore):
                     INNER JOIN event_json USING (event_id)
                     LEFT JOIN rejections USING (event_id)
                     WHERE
-                        prev_event_id IN (%s)
-                        AND NOT events.outlier
-                """ % (
-                    ",".join("?" for _ in to_check),
+                        NOT events.outlier
+                        AND
+                """
+                clause, args = make_in_list_sql_clause(
+                    self.database_engine, "prev_event_id", to_check
                 )
-                txn.execute(sql, to_check)
+                txn.execute(sql + clause, list(args))
 
                 for prev_event_id, event_id, metadata, rejected in txn:
                     if event_id in graph:
@@ -397,3 +416,90 @@ class EventsBackgroundUpdatesStore(BackgroundUpdateStore):
             )
 
         return num_handled
+
+    @defer.inlineCallbacks
+    def _redactions_received_ts(self, progress, batch_size):
+        """Handles filling out the `received_ts` column in redactions.
+        """
+        last_event_id = progress.get("last_event_id", "")
+
+        def _redactions_received_ts_txn(txn):
+            # Fetch the set of event IDs that we want to update
+            sql = """
+                SELECT event_id FROM redactions
+                WHERE event_id > ?
+                ORDER BY event_id ASC
+                LIMIT ?
+            """
+
+            txn.execute(sql, (last_event_id, batch_size))
+
+            rows = txn.fetchall()
+            if not rows:
+                return 0
+
+            upper_event_id, = rows[-1]
+
+            # Update the redactions with the received_ts.
+            #
+            # Note: Not all events have an associated received_ts, so we
+            # fallback to using origin_server_ts. If we for some reason don't
+            # have an origin_server_ts, lets just use the current timestamp.
+            #
+            # We don't want to leave it null, as then we'll never try and
+            # censor those redactions.
+            sql = """
+                UPDATE redactions
+                SET received_ts = (
+                    SELECT COALESCE(received_ts, origin_server_ts, ?) FROM events
+                    WHERE events.event_id = redactions.event_id
+                )
+                WHERE ? <= event_id AND event_id <= ?
+            """
+
+            txn.execute(sql, (self._clock.time_msec(), last_event_id, upper_event_id))
+
+            self._background_update_progress_txn(
+                txn, "redactions_received_ts", {"last_event_id": upper_event_id}
+            )
+
+            return len(rows)
+
+        count = yield self.runInteraction(
+            "_redactions_received_ts", _redactions_received_ts_txn
+        )
+
+        if not count:
+            yield self._end_background_update("redactions_received_ts")
+
+        return count
+
+    @defer.inlineCallbacks
+    def _event_fix_redactions_bytes(self, progress, batch_size):
+        """Undoes hex encoded censored redacted event JSON.
+        """
+
+        def _event_fix_redactions_bytes_txn(txn):
+            # This update is quite fast due to new index.
+            txn.execute(
+                """
+                UPDATE event_json
+                SET
+                    json = convert_from(json::bytea, 'utf8')
+                FROM redactions
+                WHERE
+                    redactions.have_censored
+                    AND event_json.event_id = redactions.redacts
+                    AND json NOT LIKE '{%';
+                """
+            )
+
+            txn.execute("DROP INDEX redactions_censored_redacts")
+
+        yield self.runInteraction(
+            "_event_fix_redactions_bytes", _event_fix_redactions_bytes_txn
+        )
+
+        yield self._end_background_update("event_fix_redactions_bytes")
+
+        return 1
diff --git a/synapse/storage/events_worker.py b/synapse/storage/events_worker.py
index c6fa7f82fd..4c4b76bd93 100644
--- a/synapse/storage/events_worker.py
+++ b/synapse/storage/events_worker.py
@@ -31,12 +31,11 @@ from synapse.events.snapshot import EventContext  # noqa: F401
 from synapse.events.utils import prune_event
 from synapse.logging.context import LoggingContext, PreserveLoggingContext
 from synapse.metrics.background_process_metrics import run_as_background_process
+from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
 from synapse.types import get_domain_from_id
 from synapse.util import batch_iter
 from synapse.util.metrics import Measure
 
-from ._base import SQLBaseStore
-
 logger = logging.getLogger(__name__)
 
 
@@ -238,6 +237,20 @@ class EventsWorkerStore(SQLBaseStore):
             # we have to recheck auth now.
 
             if not allow_rejected and entry.event.type == EventTypes.Redaction:
+                if not hasattr(entry.event, "redacts"):
+                    # A redacted redaction doesn't have a `redacts` key, in
+                    # which case lets just withhold the event.
+                    #
+                    # Note: Most of the time if the redactions has been
+                    # redacted we still have the un-redacted event in the DB
+                    # and so we'll still see the `redacts` key. However, this
+                    # isn't always true e.g. if we have censored the event.
+                    logger.debug(
+                        "Withholding redaction event %s as we don't have redacts key",
+                        event_id,
+                    )
+                    continue
+
                 redacted_event_id = entry.event.redacts
                 event_map = yield self._get_events_from_cache_or_db([redacted_event_id])
                 original_event_entry = event_map.get(redacted_event_id)
@@ -609,10 +622,14 @@ class EventsWorkerStore(SQLBaseStore):
                 " rej.reason "
                 " FROM event_json as e"
                 " LEFT JOIN rejections as rej USING (event_id)"
-                " WHERE e.event_id IN (%s)"
-            ) % (",".join(["?"] * len(evs)),)
+                " WHERE "
+            )
 
-            txn.execute(sql, evs)
+            clause, args = make_in_list_sql_clause(
+                txn.database_engine, "e.event_id", evs
+            )
+
+            txn.execute(sql + clause, args)
 
             for row in txn:
                 event_id = row[0]
@@ -626,11 +643,11 @@ class EventsWorkerStore(SQLBaseStore):
                 }
 
             # check for redactions
-            redactions_sql = (
-                "SELECT event_id, redacts FROM redactions WHERE redacts IN (%s)"
-            ) % (",".join(["?"] * len(evs)),)
+            redactions_sql = "SELECT event_id, redacts FROM redactions WHERE "
+
+            clause, args = make_in_list_sql_clause(txn.database_engine, "redacts", evs)
 
-            txn.execute(redactions_sql, evs)
+            txn.execute(redactions_sql + clause, args)
 
             for (redacter, redacted) in txn:
                 d = event_dict.get(redacted)
@@ -739,10 +756,11 @@ class EventsWorkerStore(SQLBaseStore):
         results = set()
 
         def have_seen_events_txn(txn, chunk):
-            sql = "SELECT event_id FROM events as e WHERE e.event_id IN (%s)" % (
-                ",".join("?" * len(chunk)),
+            sql = "SELECT event_id FROM events as e WHERE "
+            clause, args = make_in_list_sql_clause(
+                txn.database_engine, "e.event_id", chunk
             )
-            txn.execute(sql, chunk)
+            txn.execute(sql + clause, args)
             for (event_id,) in txn:
                 results.add(event_id)
 
diff --git a/synapse/storage/filtering.py b/synapse/storage/filtering.py
index 23b48f6cea..7c2a7da836 100644
--- a/synapse/storage/filtering.py
+++ b/synapse/storage/filtering.py
@@ -51,7 +51,7 @@ class FilteringStore(SQLBaseStore):
                 "SELECT filter_id FROM user_filters "
                 "WHERE user_id = ? AND filter_json = ?"
             )
-            txn.execute(sql, (user_localpart, def_json))
+            txn.execute(sql, (user_localpart, bytearray(def_json)))
             filter_id_response = txn.fetchone()
             if filter_id_response is not None:
                 return filter_id_response[0]
@@ -68,7 +68,7 @@ class FilteringStore(SQLBaseStore):
                 "INSERT INTO user_filters (user_id, filter_id, filter_json)"
                 "VALUES(?, ?, ?)"
             )
-            txn.execute(sql, (user_localpart, filter_id, def_json))
+            txn.execute(sql, (user_localpart, filter_id, bytearray(def_json)))
 
             return filter_id
 
diff --git a/synapse/storage/media_repository.py b/synapse/storage/media_repository.py
index 6b1238ce4a..84b5f3ad5e 100644
--- a/synapse/storage/media_repository.py
+++ b/synapse/storage/media_repository.py
@@ -15,11 +15,9 @@
 from synapse.storage.background_updates import BackgroundUpdateStore
 
 
-class MediaRepositoryStore(BackgroundUpdateStore):
-    """Persistence for attachments and avatars"""
-
+class MediaRepositoryBackgroundUpdateStore(BackgroundUpdateStore):
     def __init__(self, db_conn, hs):
-        super(MediaRepositoryStore, self).__init__(db_conn, hs)
+        super(MediaRepositoryBackgroundUpdateStore, self).__init__(db_conn, hs)
 
         self.register_background_index_update(
             update_name="local_media_repository_url_idx",
@@ -29,6 +27,13 @@ class MediaRepositoryStore(BackgroundUpdateStore):
             where_clause="url_cache IS NOT NULL",
         )
 
+
+class MediaRepositoryStore(MediaRepositoryBackgroundUpdateStore):
+    """Persistence for attachments and avatars"""
+
+    def __init__(self, db_conn, hs):
+        super(MediaRepositoryStore, self).__init__(db_conn, hs)
+
     def get_local_media(self, media_id):
         """Get the metadata for a local piece of media
         Returns:
diff --git a/synapse/storage/monthly_active_users.py b/synapse/storage/monthly_active_users.py
index 752e9788a2..3803604be7 100644
--- a/synapse/storage/monthly_active_users.py
+++ b/synapse/storage/monthly_active_users.py
@@ -32,7 +32,6 @@ class MonthlyActiveUsersStore(SQLBaseStore):
         super(MonthlyActiveUsersStore, self).__init__(None, hs)
         self._clock = hs.get_clock()
         self.hs = hs
-        self.reserved_users = ()
         # Do not add more reserved users than the total allowable number
         self._new_transaction(
             dbconn,
@@ -51,7 +50,6 @@ class MonthlyActiveUsersStore(SQLBaseStore):
             txn (cursor):
             threepids (list[dict]): List of threepid dicts to reserve
         """
-        reserved_user_list = []
 
         for tp in threepids:
             user_id = self.get_user_id_by_threepid_txn(txn, tp["medium"], tp["address"])
@@ -60,10 +58,8 @@ class MonthlyActiveUsersStore(SQLBaseStore):
                 is_support = self.is_support_user_txn(txn, user_id)
                 if not is_support:
                     self.upsert_monthly_active_user_txn(txn, user_id)
-                    reserved_user_list.append(user_id)
             else:
                 logger.warning("mau limit reserved threepid %s not found in db" % tp)
-        self.reserved_users = tuple(reserved_user_list)
 
     @defer.inlineCallbacks
     def reap_monthly_active_users(self):
@@ -74,8 +70,11 @@ class MonthlyActiveUsersStore(SQLBaseStore):
             Deferred[]
         """
 
-        def _reap_users(txn):
-            # Purge stale users
+        def _reap_users(txn, reserved_users):
+            """
+            Args:
+                reserved_users (tuple): reserved users to preserve
+            """
 
             thirty_days_ago = int(self._clock.time_msec()) - (1000 * 60 * 60 * 24 * 30)
             query_args = [thirty_days_ago]
@@ -83,20 +82,19 @@ class MonthlyActiveUsersStore(SQLBaseStore):
 
             # Need if/else since 'AND user_id NOT IN ({})' fails on Postgres
             # when len(reserved_users) == 0. Works fine on sqlite.
-            if len(self.reserved_users) > 0:
+            if len(reserved_users) > 0:
                 # questionmarks is a hack to overcome sqlite not supporting
                 # tuples in 'WHERE IN %s'
-                questionmarks = "?" * len(self.reserved_users)
+                question_marks = ",".join("?" * len(reserved_users))
 
-                query_args.extend(self.reserved_users)
-                sql = base_sql + """ AND user_id NOT IN ({})""".format(
-                    ",".join(questionmarks)
-                )
+                query_args.extend(reserved_users)
+                sql = base_sql + " AND user_id NOT IN ({})".format(question_marks)
             else:
                 sql = base_sql
 
             txn.execute(sql, query_args)
 
+            max_mau_value = self.hs.config.max_mau_value
             if self.hs.config.limit_usage_by_mau:
                 # If MAU user count still exceeds the MAU threshold, then delete on
                 # a least recently active basis.
@@ -106,31 +104,52 @@ class MonthlyActiveUsersStore(SQLBaseStore):
                 # While Postgres does not require 'LIMIT', but also does not support
                 # negative LIMIT values. So there is no way to write it that both can
                 # support
-                safe_guard = self.hs.config.max_mau_value - len(self.reserved_users)
-                # Must be greater than zero for postgres
-                safe_guard = safe_guard if safe_guard > 0 else 0
-                query_args = [safe_guard]
-
-                base_sql = """
-                    DELETE FROM monthly_active_users
-                    WHERE user_id NOT IN (
-                        SELECT user_id FROM monthly_active_users
-                        ORDER BY timestamp DESC
-                        LIMIT ?
+                if len(reserved_users) == 0:
+                    sql = """
+                        DELETE FROM monthly_active_users
+                        WHERE user_id NOT IN (
+                            SELECT user_id FROM monthly_active_users
+                            ORDER BY timestamp DESC
+                            LIMIT ?
                         )
-                    """
+                        """
+                    txn.execute(sql, (max_mau_value,))
                 # Need if/else since 'AND user_id NOT IN ({})' fails on Postgres
                 # when len(reserved_users) == 0. Works fine on sqlite.
-                if len(self.reserved_users) > 0:
-                    query_args.extend(self.reserved_users)
-                    sql = base_sql + """ AND user_id NOT IN ({})""".format(
-                        ",".join(questionmarks)
-                    )
                 else:
-                    sql = base_sql
-                txn.execute(sql, query_args)
+                    # Must be >= 0 for postgres
+                    num_of_non_reserved_users_to_remove = max(
+                        max_mau_value - len(reserved_users), 0
+                    )
+
+                    # It is important to filter reserved users twice to guard
+                    # against the case where the reserved user is present in the
+                    # SELECT, meaning that a legitmate mau is deleted.
+                    sql = """
+                        DELETE FROM monthly_active_users
+                        WHERE user_id NOT IN (
+                            SELECT user_id FROM monthly_active_users
+                            WHERE user_id NOT IN ({})
+                            ORDER BY timestamp DESC
+                            LIMIT ?
+                        )
+                        AND user_id NOT IN ({})
+                    """.format(
+                        question_marks, question_marks
+                    )
+
+                    query_args = [
+                        *reserved_users,
+                        num_of_non_reserved_users_to_remove,
+                        *reserved_users,
+                    ]
 
-        yield self.runInteraction("reap_monthly_active_users", _reap_users)
+                    txn.execute(sql, query_args)
+
+        reserved_users = yield self.get_registered_reserved_users()
+        yield self.runInteraction(
+            "reap_monthly_active_users", _reap_users, reserved_users
+        )
         # It seems poor to invalidate the whole cache, Postgres supports
         # 'Returning' which would allow me to invalidate only the
         # specific users, but sqlite has no way to do this and instead
@@ -159,21 +178,25 @@ class MonthlyActiveUsersStore(SQLBaseStore):
         return self.runInteraction("count_users", _count_users)
 
     @defer.inlineCallbacks
-    def get_registered_reserved_users_count(self):
-        """Of the reserved threepids defined in config, how many are associated
+    def get_registered_reserved_users(self):
+        """Of the reserved threepids defined in config, which are associated
         with registered users?
 
         Returns:
-            Defered[int]: Number of real reserved users
+            Defered[list]: Real reserved users
         """
-        count = 0
-        for tp in self.hs.config.mau_limits_reserved_threepids:
+        users = []
+
+        for tp in self.hs.config.mau_limits_reserved_threepids[
+            : self.hs.config.max_mau_value
+        ]:
             user_id = yield self.hs.get_datastore().get_user_id_by_threepid(
                 tp["medium"], tp["address"]
             )
             if user_id:
-                count = count + 1
-        return count
+                users.append(user_id)
+
+        return users
 
     @defer.inlineCallbacks
     def upsert_monthly_active_user(self, user_id):
diff --git a/synapse/storage/presence.py b/synapse/storage/presence.py
index 5db6f2d84a..3a641f538b 100644
--- a/synapse/storage/presence.py
+++ b/synapse/storage/presence.py
@@ -18,11 +18,10 @@ from collections import namedtuple
 from twisted.internet import defer
 
 from synapse.api.constants import PresenceState
+from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
 from synapse.util import batch_iter
 from synapse.util.caches.descriptors import cached, cachedList
 
-from ._base import SQLBaseStore
-
 
 class UserPresenceState(
     namedtuple(
@@ -119,14 +118,13 @@ class PresenceStore(SQLBaseStore):
         )
 
         # Delete old rows to stop database from getting really big
-        sql = (
-            "DELETE FROM presence_stream WHERE" " stream_id < ?" " AND user_id IN (%s)"
-        )
+        sql = "DELETE FROM presence_stream WHERE stream_id < ? AND "
 
         for states in batch_iter(presence_states, 50):
-            args = [stream_id]
-            args.extend(s.user_id for s in states)
-            txn.execute(sql % (",".join("?" for _ in states),), args)
+            clause, args = make_in_list_sql_clause(
+                self.database_engine, "user_id", [s.user_id for s in states]
+            )
+            txn.execute(sql + clause, [stream_id] + list(args))
 
     def get_all_presence_updates(self, last_id, current_id):
         if last_id == current_id:
diff --git a/synapse/storage/push_rule.py b/synapse/storage/push_rule.py
index a6517c4cf3..c4e24edff2 100644
--- a/synapse/storage/push_rule.py
+++ b/synapse/storage/push_rule.py
@@ -183,8 +183,8 @@ class PushRulesWorkerStore(
         return results
 
     @defer.inlineCallbacks
-    def move_push_rule_from_room_to_room(self, new_room_id, user_id, rule):
-        """Move a single push rule from one room to another for a specific user.
+    def copy_push_rule_from_room_to_room(self, new_room_id, user_id, rule):
+        """Copy a single push rule from one room to another for a specific user.
 
         Args:
             new_room_id (str): ID of the new room.
@@ -209,14 +209,11 @@ class PushRulesWorkerStore(
             actions=rule["actions"],
         )
 
-        # Delete push rule for the old room
-        yield self.delete_push_rule(user_id, rule["rule_id"])
-
     @defer.inlineCallbacks
-    def move_push_rules_from_room_to_room_for_user(
+    def copy_push_rules_from_room_to_room_for_user(
         self, old_room_id, new_room_id, user_id
     ):
-        """Move all of the push rules from one room to another for a specific
+        """Copy all of the push rules from one room to another for a specific
         user.
 
         Args:
@@ -227,15 +224,14 @@ class PushRulesWorkerStore(
         # Retrieve push rules for this user
         user_push_rules = yield self.get_push_rules_for_user(user_id)
 
-        # Get rules relating to the old room, move them to the new room, then
-        # delete them from the old room
+        # Get rules relating to the old room and copy them to the new room
         for rule in user_push_rules:
             conditions = rule.get("conditions", [])
             if any(
                 (c.get("key") == "room_id" and c.get("pattern") == old_room_id)
                 for c in conditions
             ):
-                self.move_push_rule_from_room_to_room(new_room_id, user_id, rule)
+                yield self.copy_push_rule_from_room_to_room(new_room_id, user_id, rule)
 
     @defer.inlineCallbacks
     def bulk_get_push_rules_for_room(self, event, context):
diff --git a/synapse/storage/pusher.py b/synapse/storage/pusher.py
index 3e0e834a62..b12e80440a 100644
--- a/synapse/storage/pusher.py
+++ b/synapse/storage/pusher.py
@@ -241,7 +241,7 @@ class PusherStore(PusherWorkerStore):
                     "device_display_name": device_display_name,
                     "ts": pushkey_ts,
                     "lang": lang,
-                    "data": encode_canonical_json(data),
+                    "data": bytearray(encode_canonical_json(data)),
                     "last_stream_ordering": last_stream_ordering,
                     "profile_tag": profile_tag,
                     "id": stream_id,
diff --git a/synapse/storage/receipts.py b/synapse/storage/receipts.py
index 290ddb30e8..0c24430f28 100644
--- a/synapse/storage/receipts.py
+++ b/synapse/storage/receipts.py
@@ -21,12 +21,11 @@ from canonicaljson import json
 
 from twisted.internet import defer
 
+from synapse.storage._base import SQLBaseStore, make_in_list_sql_clause
+from synapse.storage.util.id_generators import StreamIdGenerator
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks, cachedList
 from synapse.util.caches.stream_change_cache import StreamChangeCache
 
-from ._base import SQLBaseStore
-from .util.id_generators import StreamIdGenerator
-
 logger = logging.getLogger(__name__)
 
 
@@ -217,24 +216,26 @@ class ReceiptsWorkerStore(SQLBaseStore):
 
         def f(txn):
             if from_key:
-                sql = (
-                    "SELECT * FROM receipts_linearized WHERE"
-                    " room_id IN (%s) AND stream_id > ? AND stream_id <= ?"
-                ) % (",".join(["?"] * len(room_ids)))
-                args = list(room_ids)
-                args.extend([from_key, to_key])
+                sql = """
+                    SELECT * FROM receipts_linearized WHERE
+                    stream_id > ? AND stream_id <= ? AND
+                """
+                clause, args = make_in_list_sql_clause(
+                    self.database_engine, "room_id", room_ids
+                )
 
-                txn.execute(sql, args)
+                txn.execute(sql + clause, [from_key, to_key] + list(args))
             else:
-                sql = (
-                    "SELECT * FROM receipts_linearized WHERE"
-                    " room_id IN (%s) AND stream_id <= ?"
-                ) % (",".join(["?"] * len(room_ids)))
+                sql = """
+                    SELECT * FROM receipts_linearized WHERE
+                    stream_id <= ? AND
+                """
 
-                args = list(room_ids)
-                args.append(to_key)
+                clause, args = make_in_list_sql_clause(
+                    self.database_engine, "room_id", room_ids
+                )
 
-                txn.execute(sql, args)
+                txn.execute(sql + clause, [to_key] + list(args))
 
             return self.cursor_to_dict(txn)
 
@@ -433,13 +434,19 @@ class ReceiptsStore(ReceiptsWorkerStore):
             # we need to points in graph -> linearized form.
             # TODO: Make this better.
             def graph_to_linear(txn):
-                query = (
-                    "SELECT event_id WHERE room_id = ? AND stream_ordering IN ("
-                    " SELECT max(stream_ordering) WHERE event_id IN (%s)"
-                    ")"
-                ) % (",".join(["?"] * len(event_ids)))
+                clause, args = make_in_list_sql_clause(
+                    self.database_engine, "event_id", event_ids
+                )
+
+                sql = """
+                    SELECT event_id WHERE room_id = ? AND stream_ordering IN (
+                        SELECT max(stream_ordering) WHERE %s
+                    )
+                """ % (
+                    clause,
+                )
 
-                txn.execute(query, [room_id] + event_ids)
+                txn.execute(sql, [room_id] + list(args))
                 rows = txn.fetchall()
                 if rows:
                     return rows[0][0]
diff --git a/synapse/storage/registration.py b/synapse/storage/registration.py
index 5138792a5f..6c5b29288a 100644
--- a/synapse/storage/registration.py
+++ b/synapse/storage/registration.py
@@ -22,9 +22,10 @@ from six import iterkeys
 from six.moves import range
 
 from twisted.internet import defer
+from twisted.internet.defer import Deferred
 
 from synapse.api.constants import UserTypes
-from synapse.api.errors import Codes, StoreError, ThreepidValidationError
+from synapse.api.errors import Codes, StoreError, SynapseError, ThreepidValidationError
 from synapse.metrics.background_process_metrics import run_as_background_process
 from synapse.storage import background_updates
 from synapse.storage._base import SQLBaseStore
@@ -323,6 +324,19 @@ class RegistrationWorkerStore(SQLBaseStore):
         return None
 
     @cachedInlineCallbacks()
+    def is_real_user(self, user_id):
+        """Determines if the user is a real user, ie does not have a 'user_type'.
+
+        Args:
+            user_id (str): user id to test
+
+        Returns:
+            Deferred[bool]: True if user 'user_type' is null or empty string
+        """
+        res = yield self.runInteraction("is_real_user", self.is_real_user_txn, user_id)
+        return res
+
+    @cachedInlineCallbacks()
     def is_support_user(self, user_id):
         """Determines if the user is of type UserTypes.SUPPORT
 
@@ -337,6 +351,16 @@ class RegistrationWorkerStore(SQLBaseStore):
         )
         return res
 
+    def is_real_user_txn(self, txn, user_id):
+        res = self._simple_select_one_onecol_txn(
+            txn=txn,
+            table="users",
+            keyvalues={"name": user_id},
+            retcol="user_type",
+            allow_none=True,
+        )
+        return res is None
+
     def is_support_user_txn(self, txn, user_id):
         res = self._simple_select_one_onecol_txn(
             txn=txn,
@@ -361,6 +385,26 @@ class RegistrationWorkerStore(SQLBaseStore):
 
         return self.runInteraction("get_users_by_id_case_insensitive", f)
 
+    async def get_user_by_external_id(
+        self, auth_provider: str, external_id: str
+    ) -> str:
+        """Look up a user by their external auth id
+
+        Args:
+            auth_provider: identifier for the remote auth provider
+            external_id: id on that system
+
+        Returns:
+            str|None: the mxid of the user, or None if they are not known
+        """
+        return await self._simple_select_one_onecol(
+            table="user_external_ids",
+            keyvalues={"auth_provider": auth_provider, "external_id": external_id},
+            retcol="user_id",
+            allow_none=True,
+            desc="get_user_by_external_id",
+        )
+
     @defer.inlineCallbacks
     def count_all_users(self):
         """Counts all users registered on the homeserver."""
@@ -422,6 +466,20 @@ class RegistrationWorkerStore(SQLBaseStore):
         return ret
 
     @defer.inlineCallbacks
+    def count_real_users(self):
+        """Counts all users without a special user_type registered on the homeserver."""
+
+        def _count_users(txn):
+            txn.execute("SELECT COUNT(*) AS users FROM users where user_type is null")
+            rows = self.cursor_to_dict(txn)
+            if rows:
+                return rows[0]["users"]
+            return 0
+
+        ret = yield self.runInteraction("count_real_users", _count_users)
+        return ret
+
+    @defer.inlineCallbacks
     def find_next_generated_user_id_localpart(self):
         """
         Gets the localpart of the next generated user ID.
@@ -435,7 +493,9 @@ class RegistrationWorkerStore(SQLBaseStore):
         """
 
         def _find_next_generated_user_id(txn):
-            txn.execute("SELECT name FROM users")
+            # We bound between '@1' and '@a' to avoid pulling the entire table
+            # out.
+            txn.execute("SELECT name FROM users WHERE '@1' <= name AND name < '@a'")
 
             regex = re.compile(r"^@(\d+):")
 
@@ -458,7 +518,7 @@ class RegistrationWorkerStore(SQLBaseStore):
         )
 
     @defer.inlineCallbacks
-    def get_user_id_by_threepid(self, medium, address, require_verified=False):
+    def get_user_id_by_threepid(self, medium, address):
         """Returns user id from threepid
 
         Args:
@@ -549,6 +609,26 @@ class RegistrationWorkerStore(SQLBaseStore):
             desc="add_user_bound_threepid",
         )
 
+    def user_get_bound_threepids(self, user_id):
+        """Get the threepids that a user has bound to an identity server through the homeserver
+        The homeserver remembers where binds to an identity server occurred. Using this
+        method can retrieve those threepids.
+
+        Args:
+            user_id (str): The ID of the user to retrieve threepids for
+
+        Returns:
+            Deferred[list[dict]]: List of dictionaries containing the following:
+                medium (str): The medium of the threepid (e.g "email")
+                address (str): The address of the threepid (e.g "bob@example.com")
+        """
+        return self._simple_select_list(
+            table="user_threepid_id_server",
+            keyvalues={"user_id": user_id},
+            retcols=["medium", "address"],
+            desc="user_get_bound_threepids",
+        )
+
     def remove_user_bound_threepid(self, user_id, medium, address, id_server):
         """The server proxied an unbind request to the given identity server on
         behalf of the given user, so we remove the mapping of threepid to
@@ -618,24 +698,37 @@ class RegistrationWorkerStore(SQLBaseStore):
         self, medium, client_secret, address=None, sid=None, validated=True
     ):
         """Gets a session_id and last_send_attempt (if available) for a
-        client_secret/medium/(address|session_id) combo
+        combination of validation metadata
 
         Args:
             medium (str|None): The medium of the 3PID
             address (str|None): The address of the 3PID
             sid (str|None): The ID of the validation session
-            client_secret (str|None): A unique string provided by the client to
-                help identify this validation attempt
+            client_secret (str): A unique string provided by the client to help identify this
+                validation attempt
             validated (bool|None): Whether sessions should be filtered by
                 whether they have been validated already or not. None to
                 perform no filtering
 
         Returns:
-            deferred {str, int}|None: A dict containing the
-                latest session_id and send_attempt count for this 3PID.
-                Otherwise None if there hasn't been a previous attempt
+            Deferred[dict|None]: A dict containing the following:
+                * address - address of the 3pid
+                * medium - medium of the 3pid
+                * client_secret - a secret provided by the client for this validation session
+                * session_id - ID of the validation session
+                * send_attempt - a number serving to dedupe send attempts for this session
+                * validated_at - timestamp of when this session was validated if so
+
+                Otherwise None if a validation session is not found
         """
-        keyvalues = {"medium": medium, "client_secret": client_secret}
+        if not client_secret:
+            raise SynapseError(
+                400, "Missing parameter: client_secret", errcode=Codes.MISSING_PARAM
+            )
+
+        keyvalues = {"client_secret": client_secret}
+        if medium:
+            keyvalues["medium"] = medium
         if address:
             keyvalues["address"] = address
         if sid:
@@ -694,13 +787,14 @@ class RegistrationWorkerStore(SQLBaseStore):
         )
 
 
-class RegistrationStore(
+class RegistrationBackgroundUpdateStore(
     RegistrationWorkerStore, background_updates.BackgroundUpdateStore
 ):
     def __init__(self, db_conn, hs):
-        super(RegistrationStore, self).__init__(db_conn, hs)
+        super(RegistrationBackgroundUpdateStore, self).__init__(db_conn, hs)
 
         self.clock = hs.get_clock()
+        self.config = hs.config
 
         self.register_background_index_update(
             "access_tokens_device_index",
@@ -716,8 +810,6 @@ class RegistrationStore(
             columns=["creation_ts"],
         )
 
-        self._account_validity = hs.config.account_validity
-
         # we no longer use refresh tokens, but it's possible that some people
         # might have a background update queued to build this index. Just
         # clear the background update.
@@ -731,17 +823,6 @@ class RegistrationStore(
             "users_set_deactivated_flag", self._background_update_set_deactivated_flag
         )
 
-        # Create a background job for culling expired 3PID validity tokens
-        def start_cull():
-            # run as a background process to make sure that the database transactions
-            # have a logcontext to report to
-            return run_as_background_process(
-                "cull_expired_threepid_validation_tokens",
-                self.cull_expired_threepid_validation_tokens,
-            )
-
-        hs.get_clock().looping_call(start_cull, THIRTY_MINUTES_IN_MS)
-
     @defer.inlineCallbacks
     def _background_update_set_deactivated_flag(self, progress, batch_size):
         """Retrieves a list of all deactivated users and sets the 'deactivated' flag to 1
@@ -774,7 +855,7 @@ class RegistrationStore(
             rows = self.cursor_to_dict(txn)
 
             if not rows:
-                return True
+                return True, 0
 
             rows_processed_nb = 0
 
@@ -790,18 +871,66 @@ class RegistrationStore(
             )
 
             if batch_size > len(rows):
-                return True
+                return True, len(rows)
             else:
-                return False
+                return False, len(rows)
 
-        end = yield self.runInteraction(
+        end, nb_processed = yield self.runInteraction(
             "users_set_deactivated_flag", _background_update_set_deactivated_flag_txn
         )
 
         if end:
             yield self._end_background_update("users_set_deactivated_flag")
 
-        return batch_size
+        return nb_processed
+
+    @defer.inlineCallbacks
+    def _bg_user_threepids_grandfather(self, progress, batch_size):
+        """We now track which identity servers a user binds their 3PID to, so
+        we need to handle the case of existing bindings where we didn't track
+        this.
+
+        We do this by grandfathering in existing user threepids assuming that
+        they used one of the server configured trusted identity servers.
+        """
+        id_servers = set(self.config.trusted_third_party_id_servers)
+
+        def _bg_user_threepids_grandfather_txn(txn):
+            sql = """
+                INSERT INTO user_threepid_id_server
+                    (user_id, medium, address, id_server)
+                SELECT user_id, medium, address, ?
+                FROM user_threepids
+            """
+
+            txn.executemany(sql, [(id_server,) for id_server in id_servers])
+
+        if id_servers:
+            yield self.runInteraction(
+                "_bg_user_threepids_grandfather", _bg_user_threepids_grandfather_txn
+            )
+
+        yield self._end_background_update("user_threepids_grandfather")
+
+        return 1
+
+
+class RegistrationStore(RegistrationBackgroundUpdateStore):
+    def __init__(self, db_conn, hs):
+        super(RegistrationStore, self).__init__(db_conn, hs)
+
+        self._account_validity = hs.config.account_validity
+
+        # Create a background job for culling expired 3PID validity tokens
+        def start_cull():
+            # run as a background process to make sure that the database transactions
+            # have a logcontext to report to
+            return run_as_background_process(
+                "cull_expired_threepid_validation_tokens",
+                self.cull_expired_threepid_validation_tokens,
+            )
+
+        hs.get_clock().looping_call(start_cull, THIRTY_MINUTES_IN_MS)
 
     @defer.inlineCallbacks
     def add_access_token_to_user(self, user_id, token, device_id, valid_until_ms):
@@ -962,6 +1091,26 @@ class RegistrationStore(
         self._invalidate_cache_and_stream(txn, self.get_user_by_id, (user_id,))
         txn.call_after(self.is_guest.invalidate, (user_id,))
 
+    def record_user_external_id(
+        self, auth_provider: str, external_id: str, user_id: str
+    ) -> Deferred:
+        """Record a mapping from an external user id to a mxid
+
+        Args:
+            auth_provider: identifier for the remote auth provider
+            external_id: id on that system
+            user_id: complete mxid that it is mapped to
+        """
+        return self._simple_insert(
+            table="user_external_ids",
+            values={
+                "auth_provider": auth_provider,
+                "external_id": external_id,
+                "user_id": user_id,
+            },
+            desc="record_user_external_id",
+        )
+
     def user_set_password_hash(self, user_id, password_hash):
         """
         NB. This does *not* evict any cache because the one use for this
@@ -1131,36 +1280,6 @@ class RegistrationStore(
             desc="get_users_pending_deactivation",
         )
 
-    @defer.inlineCallbacks
-    def _bg_user_threepids_grandfather(self, progress, batch_size):
-        """We now track which identity servers a user binds their 3PID to, so
-        we need to handle the case of existing bindings where we didn't track
-        this.
-
-        We do this by grandfathering in existing user threepids assuming that
-        they used one of the server configured trusted identity servers.
-        """
-        id_servers = set(self.config.trusted_third_party_id_servers)
-
-        def _bg_user_threepids_grandfather_txn(txn):
-            sql = """
-                INSERT INTO user_threepid_id_server
-                    (user_id, medium, address, id_server)
-                SELECT user_id, medium, address, ?
-                FROM user_threepids
-            """
-
-            txn.executemany(sql, [(id_server,) for id_server in id_servers])
-
-        if id_servers:
-            yield self.runInteraction(
-                "_bg_user_threepids_grandfather", _bg_user_threepids_grandfather_txn
-            )
-
-        yield self._end_background_update("user_threepids_grandfather")
-
-        return 1
-
     def validate_threepid_session(self, session_id, client_secret, token, current_ts):
         """Attempt to validate a threepid session using a token
 
@@ -1172,6 +1291,10 @@ class RegistrationStore(
             current_ts (int): The current unix time in milliseconds. Used for
                 checking token expiry status
 
+        Raises:
+            ThreepidValidationError: if a matching validation token was not found or has
+                expired
+
         Returns:
             deferred str|None: A str representing a link to redirect the user
             to if there is one.
@@ -1348,17 +1471,6 @@ class RegistrationStore(
             self.clock.time_msec(),
         )
 
-    def set_user_deactivated_status_txn(self, txn, user_id, deactivated):
-        self._simple_update_one_txn(
-            txn=txn,
-            table="users",
-            keyvalues={"name": user_id},
-            updatevalues={"deactivated": 1 if deactivated else 0},
-        )
-        self._invalidate_cache_and_stream(
-            txn, self.get_user_deactivated_status, (user_id,)
-        )
-
     @defer.inlineCallbacks
     def set_user_deactivated_status(self, user_id, deactivated):
         """Set the `deactivated` property for the provided user to the provided value.
@@ -1374,3 +1486,14 @@ class RegistrationStore(
             user_id,
             deactivated,
         )
+
+    def set_user_deactivated_status_txn(self, txn, user_id, deactivated):
+        self._simple_update_one_txn(
+            txn=txn,
+            table="users",
+            keyvalues={"name": user_id},
+            updatevalues={"deactivated": 1 if deactivated else 0},
+        )
+        self._invalidate_cache_and_stream(
+            txn, self.get_user_deactivated_status, (user_id,)
+        )
diff --git a/synapse/storage/room.py b/synapse/storage/room.py
index 08e13f3a3b..43cc56fa6f 100644
--- a/synapse/storage/room.py
+++ b/synapse/storage/room.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2019 The Matrix.org Foundation C.I.C.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -16,6 +17,7 @@
 import collections
 import logging
 import re
+from typing import Optional, Tuple
 
 from canonicaljson import json
 
@@ -24,6 +26,7 @@ from twisted.internet import defer
 from synapse.api.errors import StoreError
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.search import SearchStore
+from synapse.types import ThirdPartyInstanceID
 from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
 
 logger = logging.getLogger(__name__)
@@ -63,103 +66,196 @@ class RoomWorkerStore(SQLBaseStore):
             desc="get_public_room_ids",
         )
 
-    @cached(num_args=2, max_entries=100)
-    def get_public_room_ids_at_stream_id(self, stream_id, network_tuple):
-        """Get pulbic rooms for a particular list, or across all lists.
+    def count_public_rooms(self, network_tuple, ignore_non_federatable):
+        """Counts the number of public rooms as tracked in the room_stats_current
+        and room_stats_state table.
 
         Args:
-            stream_id (int)
-            network_tuple (ThirdPartyInstanceID): The list to use (None, None)
-                means the main list, None means all lsits.
+            network_tuple (ThirdPartyInstanceID|None)
+            ignore_non_federatable (bool): If true filters out non-federatable rooms
         """
-        return self.runInteraction(
-            "get_public_room_ids_at_stream_id",
-            self.get_public_room_ids_at_stream_id_txn,
-            stream_id,
-            network_tuple=network_tuple,
-        )
-
-    def get_public_room_ids_at_stream_id_txn(self, txn, stream_id, network_tuple):
-        return {
-            rm
-            for rm, vis in self.get_published_at_stream_id_txn(
-                txn, stream_id, network_tuple=network_tuple
-            ).items()
-            if vis
-        }
 
-    def get_published_at_stream_id_txn(self, txn, stream_id, network_tuple):
-        if network_tuple:
-            # We want to get from a particular list. No aggregation required.
+        def _count_public_rooms_txn(txn):
+            query_args = []
+
+            if network_tuple:
+                if network_tuple.appservice_id:
+                    published_sql = """
+                        SELECT room_id from appservice_room_list
+                        WHERE appservice_id = ? AND network_id = ?
+                    """
+                    query_args.append(network_tuple.appservice_id)
+                    query_args.append(network_tuple.network_id)
+                else:
+                    published_sql = """
+                        SELECT room_id FROM rooms WHERE is_public
+                    """
+            else:
+                published_sql = """
+                    SELECT room_id FROM rooms WHERE is_public
+                    UNION SELECT room_id from appservice_room_list
+            """
 
             sql = """
-                SELECT room_id, visibility FROM public_room_list_stream
-                INNER JOIN (
-                    SELECT room_id, max(stream_id) AS stream_id
-                    FROM public_room_list_stream
-                    WHERE stream_id <= ? %s
-                    GROUP BY room_id
-                ) grouped USING (room_id, stream_id)
+                SELECT
+                    COALESCE(COUNT(*), 0)
+                FROM (
+                    %(published_sql)s
+                ) published
+                INNER JOIN room_stats_state USING (room_id)
+                INNER JOIN room_stats_current USING (room_id)
+                WHERE
+                    (
+                        join_rules = 'public' OR history_visibility = 'world_readable'
+                    )
+                    AND joined_members > 0
+            """ % {
+                "published_sql": published_sql
+            }
+
+            txn.execute(sql, query_args)
+            return txn.fetchone()[0]
+
+        return self.runInteraction("count_public_rooms", _count_public_rooms_txn)
+
+    @defer.inlineCallbacks
+    def get_largest_public_rooms(
+        self,
+        network_tuple: Optional[ThirdPartyInstanceID],
+        search_filter: Optional[dict],
+        limit: Optional[int],
+        bounds: Optional[Tuple[int, str]],
+        forwards: bool,
+        ignore_non_federatable: bool = False,
+    ):
+        """Gets the largest public rooms (where largest is in terms of joined
+        members, as tracked in the statistics table).
+
+        Args:
+            network_tuple
+            search_filter
+            limit: Maxmimum number of rows to return, unlimited otherwise.
+            bounds: An uppoer or lower bound to apply to result set if given,
+                consists of a joined member count and room_id (these are
+                excluded from result set).
+            forwards: true iff going forwards, going backwards otherwise
+            ignore_non_federatable: If true filters out non-federatable rooms.
+
+        Returns:
+            Rooms in order: biggest number of joined users first.
+            We then arbitrarily use the room_id as a tie breaker.
+
+        """
+
+        where_clauses = []
+        query_args = []
+
+        if network_tuple:
+            if network_tuple.appservice_id:
+                published_sql = """
+                    SELECT room_id from appservice_room_list
+                    WHERE appservice_id = ? AND network_id = ?
+                """
+                query_args.append(network_tuple.appservice_id)
+                query_args.append(network_tuple.network_id)
+            else:
+                published_sql = """
+                    SELECT room_id FROM rooms WHERE is_public
+                """
+        else:
+            published_sql = """
+                SELECT room_id FROM rooms WHERE is_public
+                UNION SELECT room_id from appservice_room_list
             """
 
-            if network_tuple.appservice_id is not None:
-                txn.execute(
-                    sql % ("AND appservice_id = ? AND network_id = ?",),
-                    (stream_id, network_tuple.appservice_id, network_tuple.network_id),
+        # Work out the bounds if we're given them, these bounds look slightly
+        # odd, but are designed to help query planner use indices by pulling
+        # out a common bound.
+        if bounds:
+            last_joined_members, last_room_id = bounds
+            if forwards:
+                where_clauses.append(
+                    """
+                        joined_members <= ? AND (
+                            joined_members < ? OR room_id < ?
+                        )
+                    """
                 )
             else:
-                txn.execute(sql % ("AND appservice_id IS NULL",), (stream_id,))
-            return dict(txn)
-        else:
-            # We want to get from all lists, so we need to aggregate the results
+                where_clauses.append(
+                    """
+                        joined_members >= ? AND (
+                            joined_members > ? OR room_id > ?
+                        )
+                    """
+                )
 
-            logger.info("Executing full list")
+            query_args += [last_joined_members, last_joined_members, last_room_id]
 
-            sql = """
-                SELECT room_id, visibility
-                FROM public_room_list_stream
-                INNER JOIN (
-                    SELECT
-                        room_id, max(stream_id) AS stream_id, appservice_id,
-                        network_id
-                    FROM public_room_list_stream
-                    WHERE stream_id <= ?
-                    GROUP BY room_id, appservice_id, network_id
-                ) grouped USING (room_id, stream_id)
-            """
+        if ignore_non_federatable:
+            where_clauses.append("is_federatable")
 
-            txn.execute(sql, (stream_id,))
+        if search_filter and search_filter.get("generic_search_term", None):
+            search_term = "%" + search_filter["generic_search_term"] + "%"
 
-            results = {}
-            # A room is visible if its visible on any list.
-            for room_id, visibility in txn:
-                results[room_id] = bool(visibility) or results.get(room_id, False)
+            where_clauses.append(
+                """
+                    (
+                        name LIKE ?
+                        OR topic LIKE ?
+                        OR canonical_alias LIKE ?
+                    )
+                """
+            )
+            query_args += [search_term, search_term, search_term]
+
+        where_clause = ""
+        if where_clauses:
+            where_clause = " AND " + " AND ".join(where_clauses)
+
+        sql = """
+            SELECT
+                room_id, name, topic, canonical_alias, joined_members,
+                avatar, history_visibility, joined_members, guest_access
+            FROM (
+                %(published_sql)s
+            ) published
+            INNER JOIN room_stats_state USING (room_id)
+            INNER JOIN room_stats_current USING (room_id)
+            WHERE
+                (
+                    join_rules = 'public' OR history_visibility = 'world_readable'
+                )
+                AND joined_members > 0
+                %(where_clause)s
+            ORDER BY joined_members %(dir)s, room_id %(dir)s
+        """ % {
+            "published_sql": published_sql,
+            "where_clause": where_clause,
+            "dir": "DESC" if forwards else "ASC",
+        }
 
-            return results
+        if limit is not None:
+            query_args.append(limit)
 
-    def get_public_room_changes(self, prev_stream_id, new_stream_id, network_tuple):
-        def get_public_room_changes_txn(txn):
-            then_rooms = self.get_public_room_ids_at_stream_id_txn(
-                txn, prev_stream_id, network_tuple
-            )
+            sql += """
+                LIMIT ?
+            """
 
-            now_rooms_dict = self.get_published_at_stream_id_txn(
-                txn, new_stream_id, network_tuple
-            )
+        def _get_largest_public_rooms_txn(txn):
+            txn.execute(sql, query_args)
 
-            now_rooms_visible = set(rm for rm, vis in now_rooms_dict.items() if vis)
-            now_rooms_not_visible = set(
-                rm for rm, vis in now_rooms_dict.items() if not vis
-            )
+            results = self.cursor_to_dict(txn)
 
-            newly_visible = now_rooms_visible - then_rooms
-            newly_unpublished = now_rooms_not_visible & then_rooms
+            if not forwards:
+                results.reverse()
 
-            return newly_visible, newly_unpublished
+            return results
 
-        return self.runInteraction(
-            "get_public_room_changes", get_public_room_changes_txn
+        ret_val = yield self.runInteraction(
+            "get_largest_public_rooms", _get_largest_public_rooms_txn
         )
+        defer.returnValue(ret_val)
 
     @cached(max_entries=10000)
     def is_room_blocked(self, room_id):
diff --git a/synapse/storage/roommember.py b/synapse/storage/roommember.py
index 4df8ebdacd..ff63487823 100644
--- a/synapse/storage/roommember.py
+++ b/synapse/storage/roommember.py
@@ -26,13 +26,15 @@ from twisted.internet import defer
 from synapse.api.constants import EventTypes, Membership
 from synapse.metrics import LaterGauge
 from synapse.metrics.background_process_metrics import run_as_background_process
-from synapse.storage._base import LoggingTransaction
+from synapse.storage._base import LoggingTransaction, make_in_list_sql_clause
+from synapse.storage.background_updates import BackgroundUpdateStore
 from synapse.storage.engines import Sqlite3Engine
 from synapse.storage.events_worker import EventsWorkerStore
 from synapse.types import get_domain_from_id
 from synapse.util.async_helpers import Linearizer
 from synapse.util.caches import intern_string
-from synapse.util.caches.descriptors import cached, cachedInlineCallbacks
+from synapse.util.caches.descriptors import cached, cachedInlineCallbacks, cachedList
+from synapse.util.metrics import Measure
 from synapse.util.stringutils import to_ascii
 
 logger = logging.getLogger(__name__)
@@ -370,6 +372,9 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         results = []
         if membership_list:
             if self._current_state_events_membership_up_to_date:
+                clause, args = make_in_list_sql_clause(
+                    self.database_engine, "c.membership", membership_list
+                )
                 sql = """
                     SELECT room_id, e.sender, c.membership, event_id, e.stream_ordering
                     FROM current_state_events AS c
@@ -377,11 +382,14 @@ class RoomMemberWorkerStore(EventsWorkerStore):
                     WHERE
                         c.type = 'm.room.member'
                         AND state_key = ?
-                        AND c.membership IN (%s)
+                        AND %s
                 """ % (
-                    ",".join("?" * len(membership_list))
+                    clause,
                 )
             else:
+                clause, args = make_in_list_sql_clause(
+                    self.database_engine, "m.membership", membership_list
+                )
                 sql = """
                     SELECT room_id, e.sender, m.membership, event_id, e.stream_ordering
                     FROM current_state_events AS c
@@ -390,12 +398,12 @@ class RoomMemberWorkerStore(EventsWorkerStore):
                     WHERE
                         c.type = 'm.room.member'
                         AND state_key = ?
-                        AND m.membership IN (%s)
+                        AND %s
                 """ % (
-                    ",".join("?" * len(membership_list))
+                    clause,
                 )
 
-            txn.execute(sql, (user_id, *membership_list))
+            txn.execute(sql, (user_id, *args))
             results = [RoomsForUser(**r) for r in self.cursor_to_dict(txn)]
 
         if do_invite:
@@ -483,6 +491,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         )
         return result
 
+    @defer.inlineCallbacks
     def get_joined_users_from_state(self, room_id, state_entry):
         state_group = state_entry.state_group
         if not state_group:
@@ -492,9 +501,12 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             # To do this we set the state_group to a new object as object() != object()
             state_group = object()
 
-        return self._get_joined_users_from_context(
-            room_id, state_group, state_entry.state, context=state_entry
-        )
+        with Measure(self._clock, "get_joined_users_from_state"):
+            return (
+                yield self._get_joined_users_from_context(
+                    room_id, state_group, state_entry.state, context=state_entry
+                )
+            )
 
     @cachedInlineCallbacks(
         num_args=2, cache_context=True, iterable=True, max_entries=100000
@@ -567,25 +579,10 @@ class RoomMemberWorkerStore(EventsWorkerStore):
                 missing_member_event_ids.append(event_id)
 
         if missing_member_event_ids:
-            rows = yield self._simple_select_many_batch(
-                table="room_memberships",
-                column="event_id",
-                iterable=missing_member_event_ids,
-                retcols=("user_id", "display_name", "avatar_url"),
-                keyvalues={"membership": Membership.JOIN},
-                batch_size=500,
-                desc="_get_joined_users_from_context",
-            )
-
-            users_in_room.update(
-                {
-                    to_ascii(row["user_id"]): ProfileInfo(
-                        avatar_url=to_ascii(row["avatar_url"]),
-                        display_name=to_ascii(row["display_name"]),
-                    )
-                    for row in rows
-                }
+            event_to_memberships = yield self._get_joined_profiles_from_event_ids(
+                missing_member_event_ids
             )
+            users_in_room.update((row for row in event_to_memberships.values() if row))
 
         if event is not None and event.type == EventTypes.Member:
             if event.membership == Membership.JOIN:
@@ -597,6 +594,47 @@ class RoomMemberWorkerStore(EventsWorkerStore):
 
         return users_in_room
 
+    @cached(max_entries=10000)
+    def _get_joined_profile_from_event_id(self, event_id):
+        raise NotImplementedError()
+
+    @cachedList(
+        cached_method_name="_get_joined_profile_from_event_id",
+        list_name="event_ids",
+        inlineCallbacks=True,
+    )
+    def _get_joined_profiles_from_event_ids(self, event_ids):
+        """For given set of member event_ids check if they point to a join
+        event and if so return the associated user and profile info.
+
+        Args:
+            event_ids (Iterable[str]): The member event IDs to lookup
+
+        Returns:
+            Deferred[dict[str, Tuple[str, ProfileInfo]|None]]: Map from event ID
+            to `user_id` and ProfileInfo (or None if not join event).
+        """
+
+        rows = yield self._simple_select_many_batch(
+            table="room_memberships",
+            column="event_id",
+            iterable=event_ids,
+            retcols=("user_id", "display_name", "avatar_url", "event_id"),
+            keyvalues={"membership": Membership.JOIN},
+            batch_size=500,
+            desc="_get_membership_from_event_ids",
+        )
+
+        return {
+            row["event_id"]: (
+                row["user_id"],
+                ProfileInfo(
+                    avatar_url=row["avatar_url"], display_name=row["display_name"]
+                ),
+            )
+            for row in rows
+        }
+
     @cachedInlineCallbacks(max_entries=10000)
     def is_host_joined(self, room_id, host):
         if "%" in host or "_" in host:
@@ -669,6 +707,7 @@ class RoomMemberWorkerStore(EventsWorkerStore):
 
         return True
 
+    @defer.inlineCallbacks
     def get_joined_hosts(self, room_id, state_entry):
         state_group = state_entry.state_group
         if not state_group:
@@ -678,9 +717,12 @@ class RoomMemberWorkerStore(EventsWorkerStore):
             # To do this we set the state_group to a new object as object() != object()
             state_group = object()
 
-        return self._get_joined_hosts(
-            room_id, state_group, state_entry.state, state_entry=state_entry
-        )
+        with Measure(self._clock, "get_joined_hosts"):
+            return (
+                yield self._get_joined_hosts(
+                    room_id, state_group, state_entry.state, state_entry=state_entry
+                )
+            )
 
     @cachedInlineCallbacks(num_args=2, max_entries=10000, iterable=True)
     # @defer.inlineCallbacks
@@ -785,9 +827,9 @@ class RoomMemberWorkerStore(EventsWorkerStore):
         return set(room_ids)
 
 
-class RoomMemberStore(RoomMemberWorkerStore):
+class RoomMemberBackgroundUpdateStore(BackgroundUpdateStore):
     def __init__(self, db_conn, hs):
-        super(RoomMemberStore, self).__init__(db_conn, hs)
+        super(RoomMemberBackgroundUpdateStore, self).__init__(db_conn, hs)
         self.register_background_update_handler(
             _MEMBERSHIP_PROFILE_UPDATE_NAME, self._background_add_membership_profile
         )
@@ -803,112 +845,6 @@ class RoomMemberStore(RoomMemberWorkerStore):
             where_clause="forgotten = 1",
         )
 
-    def _store_room_members_txn(self, txn, events, backfilled):
-        """Store a room member in the database.
-        """
-        self._simple_insert_many_txn(
-            txn,
-            table="room_memberships",
-            values=[
-                {
-                    "event_id": event.event_id,
-                    "user_id": event.state_key,
-                    "sender": event.user_id,
-                    "room_id": event.room_id,
-                    "membership": event.membership,
-                    "display_name": event.content.get("displayname", None),
-                    "avatar_url": event.content.get("avatar_url", None),
-                }
-                for event in events
-            ],
-        )
-
-        for event in events:
-            txn.call_after(
-                self._membership_stream_cache.entity_has_changed,
-                event.state_key,
-                event.internal_metadata.stream_ordering,
-            )
-            txn.call_after(
-                self.get_invited_rooms_for_user.invalidate, (event.state_key,)
-            )
-
-            # We update the local_invites table only if the event is "current",
-            # i.e., its something that has just happened. If the event is an
-            # outlier it is only current if its an "out of band membership",
-            # like a remote invite or a rejection of a remote invite.
-            is_new_state = not backfilled and (
-                not event.internal_metadata.is_outlier()
-                or event.internal_metadata.is_out_of_band_membership()
-            )
-            is_mine = self.hs.is_mine_id(event.state_key)
-            if is_new_state and is_mine:
-                if event.membership == Membership.INVITE:
-                    self._simple_insert_txn(
-                        txn,
-                        table="local_invites",
-                        values={
-                            "event_id": event.event_id,
-                            "invitee": event.state_key,
-                            "inviter": event.sender,
-                            "room_id": event.room_id,
-                            "stream_id": event.internal_metadata.stream_ordering,
-                        },
-                    )
-                else:
-                    sql = (
-                        "UPDATE local_invites SET stream_id = ?, replaced_by = ? WHERE"
-                        " room_id = ? AND invitee = ? AND locally_rejected is NULL"
-                        " AND replaced_by is NULL"
-                    )
-
-                    txn.execute(
-                        sql,
-                        (
-                            event.internal_metadata.stream_ordering,
-                            event.event_id,
-                            event.room_id,
-                            event.state_key,
-                        ),
-                    )
-
-    @defer.inlineCallbacks
-    def locally_reject_invite(self, user_id, room_id):
-        sql = (
-            "UPDATE local_invites SET stream_id = ?, locally_rejected = ? WHERE"
-            " room_id = ? AND invitee = ? AND locally_rejected is NULL"
-            " AND replaced_by is NULL"
-        )
-
-        def f(txn, stream_ordering):
-            txn.execute(sql, (stream_ordering, True, room_id, user_id))
-
-        with self._stream_id_gen.get_next() as stream_ordering:
-            yield self.runInteraction("locally_reject_invite", f, stream_ordering)
-
-    def forget(self, user_id, room_id):
-        """Indicate that user_id wishes to discard history for room_id."""
-
-        def f(txn):
-            sql = (
-                "UPDATE"
-                "  room_memberships"
-                " SET"
-                "  forgotten = 1"
-                " WHERE"
-                "  user_id = ?"
-                " AND"
-                "  room_id = ?"
-            )
-            txn.execute(sql, (user_id, room_id))
-
-            self._invalidate_cache_and_stream(txn, self.did_forget, (user_id, room_id))
-            self._invalidate_cache_and_stream(
-                txn, self.get_forgotten_rooms_for_user, (user_id,)
-            )
-
-        return self.runInteraction("forget_membership", f)
-
     @defer.inlineCallbacks
     def _background_add_membership_profile(self, progress, batch_size):
         target_min_stream_id = progress.get(
@@ -1043,6 +979,117 @@ class RoomMemberStore(RoomMemberWorkerStore):
         return row_count
 
 
+class RoomMemberStore(RoomMemberWorkerStore, RoomMemberBackgroundUpdateStore):
+    def __init__(self, db_conn, hs):
+        super(RoomMemberStore, self).__init__(db_conn, hs)
+
+    def _store_room_members_txn(self, txn, events, backfilled):
+        """Store a room member in the database.
+        """
+        self._simple_insert_many_txn(
+            txn,
+            table="room_memberships",
+            values=[
+                {
+                    "event_id": event.event_id,
+                    "user_id": event.state_key,
+                    "sender": event.user_id,
+                    "room_id": event.room_id,
+                    "membership": event.membership,
+                    "display_name": event.content.get("displayname", None),
+                    "avatar_url": event.content.get("avatar_url", None),
+                }
+                for event in events
+            ],
+        )
+
+        for event in events:
+            txn.call_after(
+                self._membership_stream_cache.entity_has_changed,
+                event.state_key,
+                event.internal_metadata.stream_ordering,
+            )
+            txn.call_after(
+                self.get_invited_rooms_for_user.invalidate, (event.state_key,)
+            )
+
+            # We update the local_invites table only if the event is "current",
+            # i.e., its something that has just happened. If the event is an
+            # outlier it is only current if its an "out of band membership",
+            # like a remote invite or a rejection of a remote invite.
+            is_new_state = not backfilled and (
+                not event.internal_metadata.is_outlier()
+                or event.internal_metadata.is_out_of_band_membership()
+            )
+            is_mine = self.hs.is_mine_id(event.state_key)
+            if is_new_state and is_mine:
+                if event.membership == Membership.INVITE:
+                    self._simple_insert_txn(
+                        txn,
+                        table="local_invites",
+                        values={
+                            "event_id": event.event_id,
+                            "invitee": event.state_key,
+                            "inviter": event.sender,
+                            "room_id": event.room_id,
+                            "stream_id": event.internal_metadata.stream_ordering,
+                        },
+                    )
+                else:
+                    sql = (
+                        "UPDATE local_invites SET stream_id = ?, replaced_by = ? WHERE"
+                        " room_id = ? AND invitee = ? AND locally_rejected is NULL"
+                        " AND replaced_by is NULL"
+                    )
+
+                    txn.execute(
+                        sql,
+                        (
+                            event.internal_metadata.stream_ordering,
+                            event.event_id,
+                            event.room_id,
+                            event.state_key,
+                        ),
+                    )
+
+    @defer.inlineCallbacks
+    def locally_reject_invite(self, user_id, room_id):
+        sql = (
+            "UPDATE local_invites SET stream_id = ?, locally_rejected = ? WHERE"
+            " room_id = ? AND invitee = ? AND locally_rejected is NULL"
+            " AND replaced_by is NULL"
+        )
+
+        def f(txn, stream_ordering):
+            txn.execute(sql, (stream_ordering, True, room_id, user_id))
+
+        with self._stream_id_gen.get_next() as stream_ordering:
+            yield self.runInteraction("locally_reject_invite", f, stream_ordering)
+
+    def forget(self, user_id, room_id):
+        """Indicate that user_id wishes to discard history for room_id."""
+
+        def f(txn):
+            sql = (
+                "UPDATE"
+                "  room_memberships"
+                " SET"
+                "  forgotten = 1"
+                " WHERE"
+                "  user_id = ?"
+                " AND"
+                "  room_id = ?"
+            )
+            txn.execute(sql, (user_id, room_id))
+
+            self._invalidate_cache_and_stream(txn, self.did_forget, (user_id, room_id))
+            self._invalidate_cache_and_stream(
+                txn, self.get_forgotten_rooms_for_user, (user_id,)
+            )
+
+        return self.runInteraction("forget_membership", f)
+
+
 class _JoinedHostsCache(object):
     """Cache for joined hosts in a room that is optimised to handle updates
     via state deltas.
diff --git a/synapse/storage/schema/delta/56/destinations_failure_ts.sql b/synapse/storage/schema/delta/56/destinations_failure_ts.sql
new file mode 100644
index 0000000000..f00889290b
--- /dev/null
+++ b/synapse/storage/schema/delta/56/destinations_failure_ts.sql
@@ -0,0 +1,25 @@
+/* Copyright 2019 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * Record the timestamp when a given server started failing
+ */
+ALTER TABLE destinations ADD failure_ts BIGINT;
+
+/* as a rough approximation, we assume that the server started failing at
+ * retry_interval before the last retry
+ */
+UPDATE destinations SET failure_ts = retry_last_ts - retry_interval
+    WHERE retry_last_ts > 0;
diff --git a/synapse/storage/schema/delta/56/destinations_retry_interval_type.sql.postgres b/synapse/storage/schema/delta/56/destinations_retry_interval_type.sql.postgres
new file mode 100644
index 0000000000..b9bbb18a91
--- /dev/null
+++ b/synapse/storage/schema/delta/56/destinations_retry_interval_type.sql.postgres
@@ -0,0 +1,18 @@
+/* Copyright 2019 The Matrix.org Foundation C.I.C
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- We want to store large retry intervals so we upgrade the column from INT
+-- to BIGINT. We don't need to do this on SQLite.
+ALTER TABLE destinations ALTER retry_interval SET DATA TYPE BIGINT;
diff --git a/synapse/storage/schema/delta/56/devices_last_seen.sql b/synapse/storage/schema/delta/56/devices_last_seen.sql
new file mode 100644
index 0000000000..dfa902d0ba
--- /dev/null
+++ b/synapse/storage/schema/delta/56/devices_last_seen.sql
@@ -0,0 +1,24 @@
+/* Copyright 2019 Matrix.org Foundation CIC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+-- Track last seen information for a device in the devices table, rather
+-- than relying on it being in the user_ips table (which we want to be able
+-- to purge old entries from)
+ALTER TABLE devices ADD COLUMN last_seen BIGINT;
+ALTER TABLE devices ADD COLUMN ip TEXT;
+ALTER TABLE devices ADD COLUMN user_agent TEXT;
+
+INSERT INTO background_updates (update_name, progress_json) VALUES
+  ('devices_last_seen', '{}');
diff --git a/synapse/storage/schema/delta/56/public_room_list_idx.sql b/synapse/storage/schema/delta/56/public_room_list_idx.sql
new file mode 100644
index 0000000000..7be31ffebb
--- /dev/null
+++ b/synapse/storage/schema/delta/56/public_room_list_idx.sql
@@ -0,0 +1,16 @@
+/* Copyright 2019 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+CREATE INDEX public_room_list_stream_network ON public_room_list_stream (appservice_id, network_id, room_id);
diff --git a/synapse/storage/schema/delta/56/redaction_censor.sql b/synapse/storage/schema/delta/56/redaction_censor.sql
new file mode 100644
index 0000000000..fe51b02309
--- /dev/null
+++ b/synapse/storage/schema/delta/56/redaction_censor.sql
@@ -0,0 +1,17 @@
+/* Copyright 2019 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+ALTER TABLE redactions ADD COLUMN have_censored BOOL NOT NULL DEFAULT false;
+CREATE INDEX redactions_have_censored ON redactions(event_id) WHERE not have_censored;
diff --git a/synapse/storage/schema/delta/56/redaction_censor2.sql b/synapse/storage/schema/delta/56/redaction_censor2.sql
new file mode 100644
index 0000000000..77a5eca499
--- /dev/null
+++ b/synapse/storage/schema/delta/56/redaction_censor2.sql
@@ -0,0 +1,20 @@
+/* Copyright 2019 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+ALTER TABLE redactions ADD COLUMN received_ts BIGINT;
+CREATE INDEX redactions_have_censored_ts ON redactions(received_ts) WHERE not have_censored;
+
+INSERT INTO background_updates (update_name, progress_json) VALUES
+  ('redactions_received_ts', '{}');
diff --git a/synapse/storage/schema/delta/56/redaction_censor3_fix_update.sql.postgres b/synapse/storage/schema/delta/56/redaction_censor3_fix_update.sql.postgres
new file mode 100644
index 0000000000..67471f3ef5
--- /dev/null
+++ b/synapse/storage/schema/delta/56/redaction_censor3_fix_update.sql.postgres
@@ -0,0 +1,25 @@
+/* Copyright 2019 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+
+-- There was a bug where we may have updated censored redactions as bytes,
+-- which can (somehow) cause json to be inserted hex encoded. These updates go
+-- and undoes any such hex encoded JSON.
+
+INSERT into background_updates (update_name, progress_json)
+  VALUES ('event_fix_redactions_bytes_create_index', '{}');
+
+INSERT into background_updates (update_name, progress_json, depends_on)
+  VALUES ('event_fix_redactions_bytes', '{}', 'event_fix_redactions_bytes_create_index');
diff --git a/synapse/storage/schema/delta/56/unique_user_filter_index.py b/synapse/storage/schema/delta/56/unique_user_filter_index.py
new file mode 100644
index 0000000000..1de8b54961
--- /dev/null
+++ b/synapse/storage/schema/delta/56/unique_user_filter_index.py
@@ -0,0 +1,52 @@
+import logging
+
+from synapse.storage.engines import PostgresEngine
+
+logger = logging.getLogger(__name__)
+
+
+"""
+This migration updates the user_filters table as follows:
+
+ - drops any (user_id, filter_id) duplicates
+ - makes the columns NON-NULLable
+ - turns the index into a UNIQUE index
+"""
+
+
+def run_upgrade(cur, database_engine, *args, **kwargs):
+    pass
+
+
+def run_create(cur, database_engine, *args, **kwargs):
+    if isinstance(database_engine, PostgresEngine):
+        select_clause = """
+            SELECT DISTINCT ON (user_id, filter_id) user_id, filter_id, filter_json
+            FROM user_filters
+        """
+    else:
+        select_clause = """
+            SELECT * FROM user_filters GROUP BY user_id, filter_id
+        """
+    sql = """
+            DROP TABLE IF EXISTS user_filters_migration;
+            DROP INDEX IF EXISTS user_filters_unique;
+            CREATE TABLE user_filters_migration (
+                user_id TEXT NOT NULL,
+                filter_id BIGINT NOT NULL,
+                filter_json BYTEA NOT NULL
+            );
+            INSERT INTO user_filters_migration (user_id, filter_id, filter_json)
+                %s;
+            CREATE UNIQUE INDEX user_filters_unique ON user_filters_migration
+                (user_id, filter_id);
+            DROP TABLE user_filters;
+            ALTER TABLE user_filters_migration RENAME TO user_filters;
+        """ % (
+        select_clause,
+    )
+
+    if isinstance(database_engine, PostgresEngine):
+        cur.execute(sql)
+    else:
+        cur.executescript(sql)
diff --git a/synapse/storage/schema/delta/56/user_external_ids.sql b/synapse/storage/schema/delta/56/user_external_ids.sql
new file mode 100644
index 0000000000..91390c4527
--- /dev/null
+++ b/synapse/storage/schema/delta/56/user_external_ids.sql
@@ -0,0 +1,24 @@
+/* Copyright 2019 The Matrix.org Foundation C.I.C.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+/*
+ * a table which records mappings from external auth providers to mxids
+ */
+CREATE TABLE IF NOT EXISTS user_external_ids (
+    auth_provider TEXT NOT NULL,
+    external_id TEXT NOT NULL,
+    user_id TEXT NOT NULL,
+    UNIQUE (auth_provider, external_id)
+);
diff --git a/synapse/storage/search.py b/synapse/storage/search.py
index df87ab6a6d..7695bf09fc 100644
--- a/synapse/storage/search.py
+++ b/synapse/storage/search.py
@@ -24,6 +24,7 @@ from canonicaljson import json
 from twisted.internet import defer
 
 from synapse.api.errors import SynapseError
+from synapse.storage._base import make_in_list_sql_clause
 from synapse.storage.engines import PostgresEngine, Sqlite3Engine
 
 from .background_updates import BackgroundUpdateStore
@@ -36,7 +37,7 @@ SearchEntry = namedtuple(
 )
 
 
-class SearchStore(BackgroundUpdateStore):
+class SearchBackgroundUpdateStore(BackgroundUpdateStore):
 
     EVENT_SEARCH_UPDATE_NAME = "event_search"
     EVENT_SEARCH_ORDER_UPDATE_NAME = "event_search_order"
@@ -44,7 +45,7 @@ class SearchStore(BackgroundUpdateStore):
     EVENT_SEARCH_USE_GIN_POSTGRES_NAME = "event_search_postgres_gin"
 
     def __init__(self, db_conn, hs):
-        super(SearchStore, self).__init__(db_conn, hs)
+        super(SearchBackgroundUpdateStore, self).__init__(db_conn, hs)
 
         if not hs.config.enable_search:
             return
@@ -289,29 +290,6 @@ class SearchStore(BackgroundUpdateStore):
 
         return num_rows
 
-    def store_event_search_txn(self, txn, event, key, value):
-        """Add event to the search table
-
-        Args:
-            txn (cursor):
-            event (EventBase):
-            key (str):
-            value (str):
-        """
-        self.store_search_entries_txn(
-            txn,
-            (
-                SearchEntry(
-                    key=key,
-                    value=value,
-                    event_id=event.event_id,
-                    room_id=event.room_id,
-                    stream_ordering=event.internal_metadata.stream_ordering,
-                    origin_server_ts=event.origin_server_ts,
-                ),
-            ),
-        )
-
     def store_search_entries_txn(self, txn, entries):
         """Add entries to the search table
 
@@ -358,6 +336,34 @@ class SearchStore(BackgroundUpdateStore):
             # This should be unreachable.
             raise Exception("Unrecognized database engine")
 
+
+class SearchStore(SearchBackgroundUpdateStore):
+    def __init__(self, db_conn, hs):
+        super(SearchStore, self).__init__(db_conn, hs)
+
+    def store_event_search_txn(self, txn, event, key, value):
+        """Add event to the search table
+
+        Args:
+            txn (cursor):
+            event (EventBase):
+            key (str):
+            value (str):
+        """
+        self.store_search_entries_txn(
+            txn,
+            (
+                SearchEntry(
+                    key=key,
+                    value=value,
+                    event_id=event.event_id,
+                    room_id=event.room_id,
+                    stream_ordering=event.internal_metadata.stream_ordering,
+                    origin_server_ts=event.origin_server_ts,
+                ),
+            ),
+        )
+
     @defer.inlineCallbacks
     def search_msgs(self, room_ids, search_term, keys):
         """Performs a full text search over events with given keys.
@@ -380,8 +386,10 @@ class SearchStore(BackgroundUpdateStore):
         # Make sure we don't explode because the person is in too many rooms.
         # We filter the results below regardless.
         if len(room_ids) < 500:
-            clauses.append("room_id IN (%s)" % (",".join(["?"] * len(room_ids)),))
-            args.extend(room_ids)
+            clause, args = make_in_list_sql_clause(
+                self.database_engine, "room_id", room_ids
+            )
+            clauses = [clause]
 
         local_clauses = []
         for key in keys:
@@ -487,8 +495,10 @@ class SearchStore(BackgroundUpdateStore):
         # Make sure we don't explode because the person is in too many rooms.
         # We filter the results below regardless.
         if len(room_ids) < 500:
-            clauses.append("room_id IN (%s)" % (",".join(["?"] * len(room_ids)),))
-            args.extend(room_ids)
+            clause, args = make_in_list_sql_clause(
+                self.database_engine, "room_id", room_ids
+            )
+            clauses = [clause]
 
         local_clauses = []
         for key in keys:
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index 1980a87108..a941a5ae3f 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -353,8 +353,158 @@ class StateFilter(object):
         return member_filter, non_member_filter
 
 
+class StateGroupBackgroundUpdateStore(SQLBaseStore):
+    """Defines functions related to state groups needed to run the state backgroud
+    updates.
+    """
+
+    def _count_state_group_hops_txn(self, txn, state_group):
+        """Given a state group, count how many hops there are in the tree.
+
+        This is used to ensure the delta chains don't get too long.
+        """
+        if isinstance(self.database_engine, PostgresEngine):
+            sql = """
+                WITH RECURSIVE state(state_group) AS (
+                    VALUES(?::bigint)
+                    UNION ALL
+                    SELECT prev_state_group FROM state_group_edges e, state s
+                    WHERE s.state_group = e.state_group
+                )
+                SELECT count(*) FROM state;
+            """
+
+            txn.execute(sql, (state_group,))
+            row = txn.fetchone()
+            if row and row[0]:
+                return row[0]
+            else:
+                return 0
+        else:
+            # We don't use WITH RECURSIVE on sqlite3 as there are distributions
+            # that ship with an sqlite3 version that doesn't support it (e.g. wheezy)
+            next_group = state_group
+            count = 0
+
+            while next_group:
+                next_group = self._simple_select_one_onecol_txn(
+                    txn,
+                    table="state_group_edges",
+                    keyvalues={"state_group": next_group},
+                    retcol="prev_state_group",
+                    allow_none=True,
+                )
+                if next_group:
+                    count += 1
+
+            return count
+
+    def _get_state_groups_from_groups_txn(
+        self, txn, groups, state_filter=StateFilter.all()
+    ):
+        results = {group: {} for group in groups}
+
+        where_clause, where_args = state_filter.make_sql_filter_clause()
+
+        # Unless the filter clause is empty, we're going to append it after an
+        # existing where clause
+        if where_clause:
+            where_clause = " AND (%s)" % (where_clause,)
+
+        if isinstance(self.database_engine, PostgresEngine):
+            # Temporarily disable sequential scans in this transaction. This is
+            # a temporary hack until we can add the right indices in
+            txn.execute("SET LOCAL enable_seqscan=off")
+
+            # The below query walks the state_group tree so that the "state"
+            # table includes all state_groups in the tree. It then joins
+            # against `state_groups_state` to fetch the latest state.
+            # It assumes that previous state groups are always numerically
+            # lesser.
+            # The PARTITION is used to get the event_id in the greatest state
+            # group for the given type, state_key.
+            # This may return multiple rows per (type, state_key), but last_value
+            # should be the same.
+            sql = """
+                WITH RECURSIVE state(state_group) AS (
+                    VALUES(?::bigint)
+                    UNION ALL
+                    SELECT prev_state_group FROM state_group_edges e, state s
+                    WHERE s.state_group = e.state_group
+                )
+                SELECT DISTINCT type, state_key, last_value(event_id) OVER (
+                    PARTITION BY type, state_key ORDER BY state_group ASC
+                    ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
+                ) AS event_id FROM state_groups_state
+                WHERE state_group IN (
+                    SELECT state_group FROM state
+                )
+            """
+
+            for group in groups:
+                args = [group]
+                args.extend(where_args)
+
+                txn.execute(sql + where_clause, args)
+                for row in txn:
+                    typ, state_key, event_id = row
+                    key = (typ, state_key)
+                    results[group][key] = event_id
+        else:
+            max_entries_returned = state_filter.max_entries_returned()
+
+            # We don't use WITH RECURSIVE on sqlite3 as there are distributions
+            # that ship with an sqlite3 version that doesn't support it (e.g. wheezy)
+            for group in groups:
+                next_group = group
+
+                while next_group:
+                    # We did this before by getting the list of group ids, and
+                    # then passing that list to sqlite to get latest event for
+                    # each (type, state_key). However, that was terribly slow
+                    # without the right indices (which we can't add until
+                    # after we finish deduping state, which requires this func)
+                    args = [next_group]
+                    args.extend(where_args)
+
+                    txn.execute(
+                        "SELECT type, state_key, event_id FROM state_groups_state"
+                        " WHERE state_group = ? " + where_clause,
+                        args,
+                    )
+                    results[group].update(
+                        ((typ, state_key), event_id)
+                        for typ, state_key, event_id in txn
+                        if (typ, state_key) not in results[group]
+                    )
+
+                    # If the number of entries in the (type,state_key)->event_id dict
+                    # matches the number of (type,state_keys) types we were searching
+                    # for, then we must have found them all, so no need to go walk
+                    # further down the tree... UNLESS our types filter contained
+                    # wildcards (i.e. Nones) in which case we have to do an exhaustive
+                    # search
+                    if (
+                        max_entries_returned is not None
+                        and len(results[group]) == max_entries_returned
+                    ):
+                        break
+
+                    next_group = self._simple_select_one_onecol_txn(
+                        txn,
+                        table="state_group_edges",
+                        keyvalues={"state_group": next_group},
+                        retcol="prev_state_group",
+                        allow_none=True,
+                    )
+
+        return results
+
+
 # this inherits from EventsWorkerStore because it calls self.get_events
-class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
+class StateGroupWorkerStore(
+    EventsWorkerStore, StateGroupBackgroundUpdateStore, SQLBaseStore
+):
     """The parts of StateGroupStore that can be called from workers.
     """
 
@@ -694,107 +844,6 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
 
         return results
 
-    def _get_state_groups_from_groups_txn(
-        self, txn, groups, state_filter=StateFilter.all()
-    ):
-        results = {group: {} for group in groups}
-
-        where_clause, where_args = state_filter.make_sql_filter_clause()
-
-        # Unless the filter clause is empty, we're going to append it after an
-        # existing where clause
-        if where_clause:
-            where_clause = " AND (%s)" % (where_clause,)
-
-        if isinstance(self.database_engine, PostgresEngine):
-            # Temporarily disable sequential scans in this transaction. This is
-            # a temporary hack until we can add the right indices in
-            txn.execute("SET LOCAL enable_seqscan=off")
-
-            # The below query walks the state_group tree so that the "state"
-            # table includes all state_groups in the tree. It then joins
-            # against `state_groups_state` to fetch the latest state.
-            # It assumes that previous state groups are always numerically
-            # lesser.
-            # The PARTITION is used to get the event_id in the greatest state
-            # group for the given type, state_key.
-            # This may return multiple rows per (type, state_key), but last_value
-            # should be the same.
-            sql = """
-                WITH RECURSIVE state(state_group) AS (
-                    VALUES(?::bigint)
-                    UNION ALL
-                    SELECT prev_state_group FROM state_group_edges e, state s
-                    WHERE s.state_group = e.state_group
-                )
-                SELECT DISTINCT type, state_key, last_value(event_id) OVER (
-                    PARTITION BY type, state_key ORDER BY state_group ASC
-                    ROWS BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
-                ) AS event_id FROM state_groups_state
-                WHERE state_group IN (
-                    SELECT state_group FROM state
-                )
-            """
-
-            for group in groups:
-                args = [group]
-                args.extend(where_args)
-
-                txn.execute(sql + where_clause, args)
-                for row in txn:
-                    typ, state_key, event_id = row
-                    key = (typ, state_key)
-                    results[group][key] = event_id
-        else:
-            max_entries_returned = state_filter.max_entries_returned()
-
-            # We don't use WITH RECURSIVE on sqlite3 as there are distributions
-            # that ship with an sqlite3 version that doesn't support it (e.g. wheezy)
-            for group in groups:
-                next_group = group
-
-                while next_group:
-                    # We did this before by getting the list of group ids, and
-                    # then passing that list to sqlite to get latest event for
-                    # each (type, state_key). However, that was terribly slow
-                    # without the right indices (which we can't add until
-                    # after we finish deduping state, which requires this func)
-                    args = [next_group]
-                    args.extend(where_args)
-
-                    txn.execute(
-                        "SELECT type, state_key, event_id FROM state_groups_state"
-                        " WHERE state_group = ? " + where_clause,
-                        args,
-                    )
-                    results[group].update(
-                        ((typ, state_key), event_id)
-                        for typ, state_key, event_id in txn
-                        if (typ, state_key) not in results[group]
-                    )
-
-                    # If the number of entries in the (type,state_key)->event_id dict
-                    # matches the number of (type,state_keys) types we were searching
-                    # for, then we must have found them all, so no need to go walk
-                    # further down the tree... UNLESS our types filter contained
-                    # wildcards (i.e. Nones) in which case we have to do an exhaustive
-                    # search
-                    if (
-                        max_entries_returned is not None
-                        and len(results[group]) == max_entries_returned
-                    ):
-                        break
-
-                    next_group = self._simple_select_one_onecol_txn(
-                        txn,
-                        table="state_group_edges",
-                        keyvalues={"state_group": next_group},
-                        retcol="prev_state_group",
-                        allow_none=True,
-                    )
-
-        return results
-
     @defer.inlineCallbacks
     def get_state_for_events(self, event_ids, state_filter=StateFilter.all()):
         """Given a list of event_ids and type tuples, return a list of state
@@ -1238,66 +1287,10 @@ class StateGroupWorkerStore(EventsWorkerStore, SQLBaseStore):
 
         return self.runInteraction("store_state_group", _store_state_group_txn)
 
-    def _count_state_group_hops_txn(self, txn, state_group):
-        """Given a state group, count how many hops there are in the tree.
-
-        This is used to ensure the delta chains don't get too long.
-        """
-        if isinstance(self.database_engine, PostgresEngine):
-            sql = """
-                WITH RECURSIVE state(state_group) AS (
-                    VALUES(?::bigint)
-                    UNION ALL
-                    SELECT prev_state_group FROM state_group_edges e, state s
-                    WHERE s.state_group = e.state_group
-                )
-                SELECT count(*) FROM state;
-            """
-
-            txn.execute(sql, (state_group,))
-            row = txn.fetchone()
-            if row and row[0]:
-                return row[0]
-            else:
-                return 0
-        else:
-            # We don't use WITH RECURSIVE on sqlite3 as there are distributions
-            # that ship with an sqlite3 version that doesn't support it (e.g. wheezy)
-            next_group = state_group
-            count = 0
-
-            while next_group:
-                next_group = self._simple_select_one_onecol_txn(
-                    txn,
-                    table="state_group_edges",
-                    keyvalues={"state_group": next_group},
-                    retcol="prev_state_group",
-                    allow_none=True,
-                )
-                if next_group:
-                    count += 1
-
-            return count
-
-
-class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
-    """ Keeps track of the state at a given event.
-
-    This is done by the concept of `state groups`. Every event is a assigned
-    a state group (identified by an arbitrary string), which references a
-    collection of state events. The current state of an event is then the
-    collection of state events referenced by the event's state group.
 
-    Hence, every change in the current state causes a new state group to be
-    generated. However, if no change happens (e.g., if we get a message event
-    with only one parent it inherits the state group from its parent.)
-
-    There are three tables:
-      * `state_groups`: Stores group name, first event with in the group and
-        room id.
-      * `event_to_state_groups`: Maps events to state groups.
-      * `state_groups_state`: Maps state group to state events.
-    """
+class StateBackgroundUpdateStore(
+    StateGroupBackgroundUpdateStore, BackgroundUpdateStore
+):
 
     STATE_GROUP_DEDUPLICATION_UPDATE_NAME = "state_group_state_deduplication"
     STATE_GROUP_INDEX_UPDATE_NAME = "state_group_state_type_index"
@@ -1305,7 +1298,7 @@ class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
     EVENT_STATE_GROUP_INDEX_UPDATE_NAME = "event_to_state_groups_sg_index"
 
     def __init__(self, db_conn, hs):
-        super(StateStore, self).__init__(db_conn, hs)
+        super(StateBackgroundUpdateStore, self).__init__(db_conn, hs)
         self.register_background_update_handler(
             self.STATE_GROUP_DEDUPLICATION_UPDATE_NAME,
             self._background_deduplicate_state,
@@ -1327,34 +1320,6 @@ class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
             columns=["state_group"],
         )
 
-    def _store_event_state_mappings_txn(self, txn, events_and_contexts):
-        state_groups = {}
-        for event, context in events_and_contexts:
-            if event.internal_metadata.is_outlier():
-                continue
-
-            # if the event was rejected, just give it the same state as its
-            # predecessor.
-            if context.rejected:
-                state_groups[event.event_id] = context.prev_group
-                continue
-
-            state_groups[event.event_id] = context.state_group
-
-        self._simple_insert_many_txn(
-            txn,
-            table="event_to_state_groups",
-            values=[
-                {"state_group": state_group_id, "event_id": event_id}
-                for event_id, state_group_id in iteritems(state_groups)
-            ],
-        )
-
-        for event_id, state_group_id in iteritems(state_groups):
-            txn.call_after(
-                self._get_state_group_for_event.prefill, (event_id,), state_group_id
-            )
-
     @defer.inlineCallbacks
     def _background_deduplicate_state(self, progress, batch_size):
         """This background update will slowly deduplicate state by reencoding
@@ -1527,3 +1492,54 @@ class StateStore(StateGroupWorkerStore, BackgroundUpdateStore):
         yield self._end_background_update(self.STATE_GROUP_INDEX_UPDATE_NAME)
 
         return 1
+
+
+class StateStore(StateGroupWorkerStore, StateBackgroundUpdateStore):
+    """ Keeps track of the state at a given event.
+
+    This is done by the concept of `state groups`. Every event is a assigned
+    a state group (identified by an arbitrary string), which references a
+    collection of state events. The current state of an event is then the
+    collection of state events referenced by the event's state group.
+
+    Hence, every change in the current state causes a new state group to be
+    generated. However, if no change happens (e.g., if we get a message event
+    with only one parent it inherits the state group from its parent.)
+
+    There are three tables:
+      * `state_groups`: Stores group name, first event with in the group and
+        room id.
+      * `event_to_state_groups`: Maps events to state groups.
+      * `state_groups_state`: Maps state group to state events.
+    """
+
+    def __init__(self, db_conn, hs):
+        super(StateStore, self).__init__(db_conn, hs)
+
+    def _store_event_state_mappings_txn(self, txn, events_and_contexts):
+        state_groups = {}
+        for event, context in events_and_contexts:
+            if event.internal_metadata.is_outlier():
+                continue
+
+            # if the event was rejected, just give it the same state as its
+            # predecessor.
+            if context.rejected:
+                state_groups[event.event_id] = context.prev_group
+                continue
+
+            state_groups[event.event_id] = context.state_group
+
+        self._simple_insert_many_txn(
+            txn,
+            table="event_to_state_groups",
+            values=[
+                {"state_group": state_group_id, "event_id": event_id}
+                for event_id, state_group_id in iteritems(state_groups)
+            ],
+        )
+
+        for event_id, state_group_id in iteritems(state_groups):
+            txn.call_after(
+                self._get_state_group_for_event.prefill, (event_id,), state_group_id
+            )
diff --git a/synapse/storage/state_deltas.py b/synapse/storage/state_deltas.py
index 5fdb442104..28f33ec18f 100644
--- a/synapse/storage/state_deltas.py
+++ b/synapse/storage/state_deltas.py
@@ -21,7 +21,7 @@ logger = logging.getLogger(__name__)
 
 
 class StateDeltasStore(SQLBaseStore):
-    def get_current_state_deltas(self, prev_stream_id):
+    def get_current_state_deltas(self, prev_stream_id: int, max_stream_id: int):
         """Fetch a list of room state changes since the given stream id
 
         Each entry in the result contains the following fields:
@@ -36,15 +36,27 @@ class StateDeltasStore(SQLBaseStore):
 
         Args:
             prev_stream_id (int): point to get changes since (exclusive)
+            max_stream_id (int): the point that we know has been correctly persisted
+               - ie, an upper limit to return changes from.
 
         Returns:
-            Deferred[list[dict]]: results
+            Deferred[tuple[int, list[dict]]: A tuple consisting of:
+               - the stream id which these results go up to
+               - list of current_state_delta_stream rows. If it is empty, we are
+                 up to date.
         """
         prev_stream_id = int(prev_stream_id)
+
+        # check we're not going backwards
+        assert prev_stream_id <= max_stream_id
+
         if not self._curr_state_delta_stream_cache.has_any_entity_changed(
             prev_stream_id
         ):
-            return []
+            # if the CSDs haven't changed between prev_stream_id and now, we
+            # know for certain that they haven't changed between prev_stream_id and
+            # max_stream_id.
+            return max_stream_id, []
 
         def get_current_state_deltas_txn(txn):
             # First we calculate the max stream id that will give us less than
@@ -54,21 +66,29 @@ class StateDeltasStore(SQLBaseStore):
             sql = """
                 SELECT stream_id, count(*)
                 FROM current_state_delta_stream
-                WHERE stream_id > ?
+                WHERE stream_id > ? AND stream_id <= ?
                 GROUP BY stream_id
                 ORDER BY stream_id ASC
                 LIMIT 100
             """
-            txn.execute(sql, (prev_stream_id,))
+            txn.execute(sql, (prev_stream_id, max_stream_id))
 
             total = 0
-            max_stream_id = prev_stream_id
-            for max_stream_id, count in txn:
+
+            for stream_id, count in txn:
                 total += count
                 if total > 100:
                     # We arbitarily limit to 100 entries to ensure we don't
                     # select toooo many.
+                    logger.debug(
+                        "Clipping current_state_delta_stream rows to stream_id %i",
+                        stream_id,
+                    )
+                    clipped_stream_id = stream_id
                     break
+            else:
+                # if there's no problem, we may as well go right up to the max_stream_id
+                clipped_stream_id = max_stream_id
 
             # Now actually get the deltas
             sql = """
@@ -77,8 +97,8 @@ class StateDeltasStore(SQLBaseStore):
                 WHERE ? < stream_id AND stream_id <= ?
                 ORDER BY stream_id ASC
             """
-            txn.execute(sql, (prev_stream_id, max_stream_id))
-            return self.cursor_to_dict(txn)
+            txn.execute(sql, (prev_stream_id, clipped_stream_id))
+            return clipped_stream_id, self.cursor_to_dict(txn)
 
         return self.runInteraction(
             "get_current_state_deltas", get_current_state_deltas_txn
diff --git a/synapse/storage/stats.py b/synapse/storage/stats.py
index 09190d684e..7c224cd3d9 100644
--- a/synapse/storage/stats.py
+++ b/synapse/storage/stats.py
@@ -332,6 +332,9 @@ class StatsStore(StateDeltasStore):
         def _bulk_update_stats_delta_txn(txn):
             for stats_type, stats_updates in updates.items():
                 for stats_id, fields in stats_updates.items():
+                    logger.info(
+                        "Updating %s stats for %s: %s", stats_type, stats_id, fields
+                    )
                     self._update_stats_delta_txn(
                         txn,
                         ts=ts,
diff --git a/synapse/storage/transactions.py b/synapse/storage/transactions.py
index b3c3bf55bc..289c117396 100644
--- a/synapse/storage/transactions.py
+++ b/synapse/storage/transactions.py
@@ -165,7 +165,7 @@ class TransactionStore(SQLBaseStore):
             txn,
             table="destinations",
             keyvalues={"destination": destination},
-            retcols=("destination", "retry_last_ts", "retry_interval"),
+            retcols=("destination", "failure_ts", "retry_last_ts", "retry_interval"),
             allow_none=True,
         )
 
@@ -174,12 +174,15 @@ class TransactionStore(SQLBaseStore):
         else:
             return None
 
-    def set_destination_retry_timings(self, destination, retry_last_ts, retry_interval):
+    def set_destination_retry_timings(
+        self, destination, failure_ts, retry_last_ts, retry_interval
+    ):
         """Sets the current retry timings for a given destination.
         Both timings should be zero if retrying is no longer occuring.
 
         Args:
             destination (str)
+            failure_ts (int|None) - when the server started failing (ms since epoch)
             retry_last_ts (int) - time of last retry attempt in unix epoch ms
             retry_interval (int) - how long until next retry in ms
         """
@@ -189,12 +192,13 @@ class TransactionStore(SQLBaseStore):
             "set_destination_retry_timings",
             self._set_destination_retry_timings,
             destination,
+            failure_ts,
             retry_last_ts,
             retry_interval,
         )
 
     def _set_destination_retry_timings(
-        self, txn, destination, retry_last_ts, retry_interval
+        self, txn, destination, failure_ts, retry_last_ts, retry_interval
     ):
 
         if self.database_engine.can_native_upsert:
@@ -202,9 +206,12 @@ class TransactionStore(SQLBaseStore):
             # resetting it) or greater than the existing retry interval.
 
             sql = """
-                INSERT INTO destinations (destination, retry_last_ts, retry_interval)
-                    VALUES (?, ?, ?)
+                INSERT INTO destinations (
+                    destination, failure_ts, retry_last_ts, retry_interval
+                )
+                    VALUES (?, ?, ?, ?)
                 ON CONFLICT (destination) DO UPDATE SET
+                        failure_ts = EXCLUDED.failure_ts,
                         retry_last_ts = EXCLUDED.retry_last_ts,
                         retry_interval = EXCLUDED.retry_interval
                     WHERE
@@ -212,7 +219,7 @@ class TransactionStore(SQLBaseStore):
                         OR destinations.retry_interval < EXCLUDED.retry_interval
             """
 
-            txn.execute(sql, (destination, retry_last_ts, retry_interval))
+            txn.execute(sql, (destination, failure_ts, retry_last_ts, retry_interval))
 
             return
 
@@ -225,7 +232,7 @@ class TransactionStore(SQLBaseStore):
             txn,
             table="destinations",
             keyvalues={"destination": destination},
-            retcols=("retry_last_ts", "retry_interval"),
+            retcols=("failure_ts", "retry_last_ts", "retry_interval"),
             allow_none=True,
         )
 
@@ -235,6 +242,7 @@ class TransactionStore(SQLBaseStore):
                 table="destinations",
                 values={
                     "destination": destination,
+                    "failure_ts": failure_ts,
                     "retry_last_ts": retry_last_ts,
                     "retry_interval": retry_interval,
                 },
@@ -245,31 +253,12 @@ class TransactionStore(SQLBaseStore):
                 "destinations",
                 keyvalues={"destination": destination},
                 updatevalues={
+                    "failure_ts": failure_ts,
                     "retry_last_ts": retry_last_ts,
                     "retry_interval": retry_interval,
                 },
             )
 
-    def get_destinations_needing_retry(self):
-        """Get all destinations which are due a retry for sending a transaction.
-
-        Returns:
-            list: A list of dicts
-        """
-
-        return self.runInteraction(
-            "get_destinations_needing_retry", self._get_destinations_needing_retry
-        )
-
-    def _get_destinations_needing_retry(self, txn):
-        query = (
-            "SELECT * FROM destinations"
-            " WHERE retry_last_ts > 0 and retry_next_ts < ?"
-        )
-
-        txn.execute(query, (self._clock.time_msec(),))
-        return self.cursor_to_dict(txn)
-
     def _start_cleanup_transactions(self):
         return run_as_background_process(
             "cleanup_transactions", self._cleanup_transactions
diff --git a/synapse/storage/user_directory.py b/synapse/storage/user_directory.py
index b5188d9bee..1b1e4751b9 100644
--- a/synapse/storage/user_directory.py
+++ b/synapse/storage/user_directory.py
@@ -32,14 +32,14 @@ logger = logging.getLogger(__name__)
 TEMP_TABLE = "_temp_populate_user_directory"
 
 
-class UserDirectoryStore(StateDeltasStore, BackgroundUpdateStore):
+class UserDirectoryBackgroundUpdateStore(StateDeltasStore, BackgroundUpdateStore):
 
     # How many records do we calculate before sending it to
     # add_users_who_share_private_rooms?
     SHARE_PRIVATE_WORKING_SET = 500
 
     def __init__(self, db_conn, hs):
-        super(UserDirectoryStore, self).__init__(db_conn, hs)
+        super(UserDirectoryBackgroundUpdateStore, self).__init__(db_conn, hs)
 
         self.server_name = hs.hostname
 
@@ -452,55 +452,6 @@ class UserDirectoryStore(StateDeltasStore, BackgroundUpdateStore):
             "update_profile_in_user_dir", _update_profile_in_user_dir_txn
         )
 
-    def remove_from_user_dir(self, user_id):
-        def _remove_from_user_dir_txn(txn):
-            self._simple_delete_txn(
-                txn, table="user_directory", keyvalues={"user_id": user_id}
-            )
-            self._simple_delete_txn(
-                txn, table="user_directory_search", keyvalues={"user_id": user_id}
-            )
-            self._simple_delete_txn(
-                txn, table="users_in_public_rooms", keyvalues={"user_id": user_id}
-            )
-            self._simple_delete_txn(
-                txn,
-                table="users_who_share_private_rooms",
-                keyvalues={"user_id": user_id},
-            )
-            self._simple_delete_txn(
-                txn,
-                table="users_who_share_private_rooms",
-                keyvalues={"other_user_id": user_id},
-            )
-            txn.call_after(self.get_user_in_directory.invalidate, (user_id,))
-
-        return self.runInteraction("remove_from_user_dir", _remove_from_user_dir_txn)
-
-    @defer.inlineCallbacks
-    def get_users_in_dir_due_to_room(self, room_id):
-        """Get all user_ids that are in the room directory because they're
-        in the given room_id
-        """
-        user_ids_share_pub = yield self._simple_select_onecol(
-            table="users_in_public_rooms",
-            keyvalues={"room_id": room_id},
-            retcol="user_id",
-            desc="get_users_in_dir_due_to_room",
-        )
-
-        user_ids_share_priv = yield self._simple_select_onecol(
-            table="users_who_share_private_rooms",
-            keyvalues={"room_id": room_id},
-            retcol="other_user_id",
-            desc="get_users_in_dir_due_to_room",
-        )
-
-        user_ids = set(user_ids_share_pub)
-        user_ids.update(user_ids_share_priv)
-
-        return user_ids
-
     def add_users_who_share_private_room(self, room_id, user_id_tuples):
         """Insert entries into the users_who_share_private_rooms table. The first
         user should be a local user.
@@ -551,6 +502,98 @@ class UserDirectoryStore(StateDeltasStore, BackgroundUpdateStore):
             "add_users_in_public_rooms", _add_users_in_public_rooms_txn
         )
 
+    def delete_all_from_user_dir(self):
+        """Delete the entire user directory
+        """
+
+        def _delete_all_from_user_dir_txn(txn):
+            txn.execute("DELETE FROM user_directory")
+            txn.execute("DELETE FROM user_directory_search")
+            txn.execute("DELETE FROM users_in_public_rooms")
+            txn.execute("DELETE FROM users_who_share_private_rooms")
+            txn.call_after(self.get_user_in_directory.invalidate_all)
+
+        return self.runInteraction(
+            "delete_all_from_user_dir", _delete_all_from_user_dir_txn
+        )
+
+    @cached()
+    def get_user_in_directory(self, user_id):
+        return self._simple_select_one(
+            table="user_directory",
+            keyvalues={"user_id": user_id},
+            retcols=("display_name", "avatar_url"),
+            allow_none=True,
+            desc="get_user_in_directory",
+        )
+
+    def update_user_directory_stream_pos(self, stream_id):
+        return self._simple_update_one(
+            table="user_directory_stream_pos",
+            keyvalues={},
+            updatevalues={"stream_id": stream_id},
+            desc="update_user_directory_stream_pos",
+        )
+
+
+class UserDirectoryStore(UserDirectoryBackgroundUpdateStore):
+
+    # How many records do we calculate before sending it to
+    # add_users_who_share_private_rooms?
+    SHARE_PRIVATE_WORKING_SET = 500
+
+    def __init__(self, db_conn, hs):
+        super(UserDirectoryStore, self).__init__(db_conn, hs)
+
+    def remove_from_user_dir(self, user_id):
+        def _remove_from_user_dir_txn(txn):
+            self._simple_delete_txn(
+                txn, table="user_directory", keyvalues={"user_id": user_id}
+            )
+            self._simple_delete_txn(
+                txn, table="user_directory_search", keyvalues={"user_id": user_id}
+            )
+            self._simple_delete_txn(
+                txn, table="users_in_public_rooms", keyvalues={"user_id": user_id}
+            )
+            self._simple_delete_txn(
+                txn,
+                table="users_who_share_private_rooms",
+                keyvalues={"user_id": user_id},
+            )
+            self._simple_delete_txn(
+                txn,
+                table="users_who_share_private_rooms",
+                keyvalues={"other_user_id": user_id},
+            )
+            txn.call_after(self.get_user_in_directory.invalidate, (user_id,))
+
+        return self.runInteraction("remove_from_user_dir", _remove_from_user_dir_txn)
+
+    @defer.inlineCallbacks
+    def get_users_in_dir_due_to_room(self, room_id):
+        """Get all user_ids that are in the room directory because they're
+        in the given room_id
+        """
+        user_ids_share_pub = yield self._simple_select_onecol(
+            table="users_in_public_rooms",
+            keyvalues={"room_id": room_id},
+            retcol="user_id",
+            desc="get_users_in_dir_due_to_room",
+        )
+
+        user_ids_share_priv = yield self._simple_select_onecol(
+            table="users_who_share_private_rooms",
+            keyvalues={"room_id": room_id},
+            retcol="other_user_id",
+            desc="get_users_in_dir_due_to_room",
+        )
+
+        user_ids = set(user_ids_share_pub)
+        user_ids.update(user_ids_share_priv)
+
+        return user_ids
+
     def remove_user_who_share_room(self, user_id, room_id):
         """
         Deletes entries in the users_who_share_*_rooms table. The first
@@ -637,31 +680,6 @@ class UserDirectoryStore(StateDeltasStore, BackgroundUpdateStore):
 
         return [room_id for room_id, in rows]
 
-    def delete_all_from_user_dir(self):
-        """Delete the entire user directory
-        """
-
-        def _delete_all_from_user_dir_txn(txn):
-            txn.execute("DELETE FROM user_directory")
-            txn.execute("DELETE FROM user_directory_search")
-            txn.execute("DELETE FROM users_in_public_rooms")
-            txn.execute("DELETE FROM users_who_share_private_rooms")
-            txn.call_after(self.get_user_in_directory.invalidate_all)
-
-        return self.runInteraction(
-            "delete_all_from_user_dir", _delete_all_from_user_dir_txn
-        )
-
-    @cached()
-    def get_user_in_directory(self, user_id):
-        return self._simple_select_one(
-            table="user_directory",
-            keyvalues={"user_id": user_id},
-            retcols=("display_name", "avatar_url"),
-            allow_none=True,
-            desc="get_user_in_directory",
-        )
-
     def get_user_directory_stream_pos(self):
         return self._simple_select_one_onecol(
             table="user_directory_stream_pos",
@@ -670,14 +688,6 @@ class UserDirectoryStore(StateDeltasStore, BackgroundUpdateStore):
             desc="get_user_directory_stream_pos",
         )
 
-    def update_user_directory_stream_pos(self, stream_id):
-        return self._simple_update_one(
-            table="user_directory_stream_pos",
-            keyvalues={},
-            updatevalues={"stream_id": stream_id},
-            desc="update_user_directory_stream_pos",
-        )
-
     @defer.inlineCallbacks
     def search_user_dir(self, user_id, search_term, limit):
         """Searches for users in directory
diff --git a/synapse/storage/user_erasure_store.py b/synapse/storage/user_erasure_store.py
index 05cabc2282..aa4f0da5f0 100644
--- a/synapse/storage/user_erasure_store.py
+++ b/synapse/storage/user_erasure_store.py
@@ -56,15 +56,15 @@ class UserErasureWorkerStore(SQLBaseStore):
         # iterate it multiple times, and (b) avoiding duplicates.
         user_ids = tuple(set(user_ids))
 
-        def _get_erased_users(txn):
-            txn.execute(
-                "SELECT user_id FROM erased_users WHERE user_id IN (%s)"
-                % (",".join("?" * len(user_ids))),
-                user_ids,
-            )
-            return set(r[0] for r in txn)
-
-        erased_users = yield self.runInteraction("are_users_erased", _get_erased_users)
+        rows = yield self._simple_select_many_batch(
+            table="erased_users",
+            column="user_id",
+            iterable=user_ids,
+            retcols=("user_id",),
+            desc="are_users_erased",
+        )
+        erased_users = set(row["user_id"] for row in rows)
+
         res = dict((u, u in erased_users) for u in user_ids)
         return res