User Cursor.__iter__ instead of fetchall

This prevents unnecessary construction of lists

15 files changed, 38 insertions, 39 deletions

diff --git a/synapse/storage/_base.py b/synapse/storage/_base.py
index 13b106bba1..93d9ed5d62 100644
--- a/synapse/storage/_base.py
+++ b/synapse/storage/_base.py
@@ -73,6 +73,9 @@ class LoggingTransaction(object):
     def __setattr__(self, name, value):
         setattr(self.txn, name, value)
 
+    def __iter__(self):
+        return self.txn.__iter__()
+
     def execute(self, sql, *args):
         self._do_execute(self.txn.execute, sql, *args)
 
@@ -357,7 +360,7 @@ class SQLBaseStore(object):
         """
         col_headers = list(intern(column[0]) for column in cursor.description)
         results = list(
-            dict(zip(col_headers, row)) for row in cursor.fetchall()
+            dict(zip(col_headers, row)) for row in cursor
         )
         return results
 
@@ -579,7 +582,7 @@ class SQLBaseStore(object):
 
         txn.execute(sql, keyvalues.values())
 
-        return [r[0] for r in txn.fetchall()]
+        return [r[0] for r in txn]
 
     def _simple_select_onecol(self, table, keyvalues, retcol,
                               desc="_simple_select_onecol"):
@@ -901,14 +904,14 @@ class SQLBaseStore(object):
 
         txn = db_conn.cursor()
         txn.execute(sql, (int(max_value),))
-        rows = txn.fetchall()
-        txn.close()
 
         cache = {
             row[0]: int(row[1])
-            for row in rows
+            for row in txn
         }
 
+        txn.close()
+
         if cache:
             min_val = min(cache.values())
         else:
diff --git a/synapse/storage/account_data.py b/synapse/storage/account_data.py
index 3fa226e92d..aa84ffc2b0 100644
--- a/synapse/storage/account_data.py
+++ b/synapse/storage/account_data.py
@@ -182,7 +182,7 @@ class AccountDataStore(SQLBaseStore):
             txn.execute(sql, (user_id, stream_id))
 
             global_account_data = {
-                row[0]: json.loads(row[1]) for row in txn.fetchall()
+                row[0]: json.loads(row[1]) for row in txn
             }
 
             sql = (
@@ -193,7 +193,7 @@ class AccountDataStore(SQLBaseStore):
             txn.execute(sql, (user_id, stream_id))
 
             account_data_by_room = {}
-            for row in txn.fetchall():
+            for row in txn:
                 room_account_data = account_data_by_room.setdefault(row[0], {})
                 room_account_data[row[1]] = json.loads(row[2])
 
diff --git a/synapse/storage/deviceinbox.py b/synapse/storage/deviceinbox.py
index 7925cb5f1b..2714519d21 100644
--- a/synapse/storage/deviceinbox.py
+++ b/synapse/storage/deviceinbox.py
@@ -178,7 +178,7 @@ class DeviceInboxStore(BackgroundUpdateStore):
                 )
                 txn.execute(sql, (user_id,))
                 message_json = ujson.dumps(messages_by_device["*"])
-                for row in txn.fetchall():
+                for row in txn:
                     # Add the message for all devices for this user on this
                     # server.
                     device = row[0]
@@ -195,7 +195,7 @@ class DeviceInboxStore(BackgroundUpdateStore):
                 # 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)
-                for row in txn.fetchall():
+                for row in txn:
                     # Only insert into the local inbox if the device exists on
                     # this server
                     device = row[0]
@@ -251,7 +251,7 @@ class DeviceInboxStore(BackgroundUpdateStore):
                 user_id, device_id, last_stream_id, current_stream_id, limit
             ))
             messages = []
-            for row in txn.fetchall():
+            for row in txn:
                 stream_pos = row[0]
                 messages.append(ujson.loads(row[1]))
             if len(messages) < limit:
@@ -340,7 +340,7 @@ class DeviceInboxStore(BackgroundUpdateStore):
                 " ORDER BY stream_id ASC"
             )
             txn.execute(sql, (last_pos, upper_pos))
-            rows.extend(txn.fetchall())
+            rows.extend(txn)
 
             return rows
 
@@ -384,7 +384,7 @@ class DeviceInboxStore(BackgroundUpdateStore):
                 destination, last_stream_id, current_stream_id, limit
             ))
             messages = []
-            for row in txn.fetchall():
+            for row in txn:
                 stream_pos = row[0]
                 messages.append(ujson.loads(row[1]))
             if len(messages) < limit:
diff --git a/synapse/storage/devices.py b/synapse/storage/devices.py
index e545b62e39..6beeff8b00 100644
--- a/synapse/storage/devices.py
+++ b/synapse/storage/devices.py
@@ -333,13 +333,12 @@ class DeviceStore(SQLBaseStore):
         txn.execute(
             sql, (destination, from_stream_id, now_stream_id, False)
         )
-        rows = txn.fetchall()
 
-        if not rows:
+        # maps (user_id, device_id) -> stream_id
+        query_map = {(r[0], r[1]): r[2] for r in txn}
+        if not query_map:
             return (now_stream_id, [])
 
-        # maps (user_id, device_id) -> stream_id
-        query_map = {(r[0], r[1]): r[2] for r in rows}
         devices = self._get_e2e_device_keys_txn(
             txn, query_map.keys(), include_all_devices=True
         )
diff --git a/synapse/storage/end_to_end_keys.py b/synapse/storage/end_to_end_keys.py
index b9f1365f92..58bde65b6c 100644
--- a/synapse/storage/end_to_end_keys.py
+++ b/synapse/storage/end_to_end_keys.py
@@ -153,7 +153,7 @@ class EndToEndKeyStore(SQLBaseStore):
             )
             txn.execute(sql, (user_id, device_id))
             result = {}
-            for algorithm, key_count in txn.fetchall():
+            for algorithm, key_count in txn:
                 result[algorithm] = key_count
             return result
         return self.runInteraction(
@@ -174,7 +174,7 @@ class EndToEndKeyStore(SQLBaseStore):
                 user_result = result.setdefault(user_id, {})
                 device_result = user_result.setdefault(device_id, {})
                 txn.execute(sql, (user_id, device_id, algorithm))
-                for key_id, key_json in txn.fetchall():
+                for key_id, key_json in txn:
                     device_result[algorithm + ":" + key_id] = key_json
                     delete.append((user_id, device_id, algorithm, key_id))
             sql = (
diff --git a/synapse/storage/event_federation.py b/synapse/storage/event_federation.py
index 0d97de2fe7..43b5b49986 100644
--- a/synapse/storage/event_federation.py
+++ b/synapse/storage/event_federation.py
@@ -74,7 +74,7 @@ class EventFederationStore(SQLBaseStore):
                     base_sql % (",".join(["?"] * len(chunk)),),
                     chunk
                 )
-                new_front.update([r[0] for r in txn.fetchall()])
+                new_front.update([r[0] for r in txn])
 
             new_front -= results
 
@@ -110,7 +110,7 @@ class EventFederationStore(SQLBaseStore):
 
         txn.execute(sql, (room_id, False,))
 
-        return dict(txn.fetchall())
+        return dict(txn)
 
     def _get_oldest_events_in_room_txn(self, txn, room_id):
         return self._simple_select_onecol_txn(
@@ -152,7 +152,7 @@ class EventFederationStore(SQLBaseStore):
         txn.execute(sql, (room_id, ))
 
         results = []
-        for event_id, depth in txn.fetchall():
+        for event_id, depth in txn:
             hashes = self._get_event_reference_hashes_txn(txn, event_id)
             prev_hashes = {
                 k: encode_base64(v) for k, v in hashes.items()
@@ -334,8 +334,7 @@ class EventFederationStore(SQLBaseStore):
 
         def get_forward_extremeties_for_room_txn(txn):
             txn.execute(sql, (stream_ordering, room_id))
-            rows = txn.fetchall()
-            return [event_id for event_id, in rows]
+            return [event_id for event_id, in txn]
 
         return self.runInteraction(
             "get_forward_extremeties_for_room",
@@ -436,7 +435,7 @@ class EventFederationStore(SQLBaseStore):
                 (room_id, event_id, False, limit - len(event_results))
             )
 
-            for row in txn.fetchall():
+            for row in txn:
                 if row[1] not in event_results:
                     queue.put((-row[0], row[1]))
 
@@ -482,7 +481,7 @@ class EventFederationStore(SQLBaseStore):
                     (room_id, event_id, False, limit - len(event_results))
                 )
 
-                for e_id, in txn.fetchall():
+                for e_id, in txn:
                     new_front.add(e_id)
 
             new_front -= earliest_events
diff --git a/synapse/storage/event_push_actions.py b/synapse/storage/event_push_actions.py
index 14543b4269..d6d8723b4a 100644
--- a/synapse/storage/event_push_actions.py
+++ b/synapse/storage/event_push_actions.py
@@ -206,7 +206,7 @@ class EventPushActionsStore(SQLBaseStore):
                 " stream_ordering >= ? AND stream_ordering <= ?"
             )
             txn.execute(sql, (min_stream_ordering, max_stream_ordering))
-            return [r[0] for r in txn.fetchall()]
+            return [r[0] for r in txn]
         ret = yield self.runInteraction("get_push_action_users_in_range", f)
         defer.returnValue(ret)
 
diff --git a/synapse/storage/events.py b/synapse/storage/events.py
index 3c8393bfe8..9f2045e8d8 100644
--- a/synapse/storage/events.py
+++ b/synapse/storage/events.py
@@ -834,7 +834,7 @@ class EventsStore(SQLBaseStore):
 
         have_persisted = {
             event_id: outlier
-            for event_id, outlier in txn.fetchall()
+            for event_id, outlier in txn
         }
 
         to_remove = set()
diff --git a/synapse/storage/prepare_database.py b/synapse/storage/prepare_database.py
index ed84db6b4b..6e623843d5 100644
--- a/synapse/storage/prepare_database.py
+++ b/synapse/storage/prepare_database.py
@@ -356,7 +356,7 @@ def _get_or_create_schema_state(txn, database_engine):
             ),
             (current_version,)
         )
-        applied_deltas = [d for d, in txn.fetchall()]
+        applied_deltas = [d for d, in txn]
         return current_version, applied_deltas, upgraded
 
     return None
diff --git a/synapse/storage/receipts.py b/synapse/storage/receipts.py
index 5cf41501ea..6b0f8c2787 100644
--- a/synapse/storage/receipts.py
+++ b/synapse/storage/receipts.py
@@ -313,10 +313,9 @@ class ReceiptsStore(SQLBaseStore):
         )
 
         txn.execute(sql, (room_id, receipt_type, user_id))
-        results = txn.fetchall()
 
-        if results and topological_ordering:
-            for to, so, _ in results:
+        if topological_ordering:
+            for to, so, _ in txn:
                 if int(to) > topological_ordering:
                     return False
                 elif int(to) == topological_ordering and int(so) >= stream_ordering:
diff --git a/synapse/storage/registration.py b/synapse/storage/registration.py
index 26be6060c3..ec2c52ab93 100644
--- a/synapse/storage/registration.py
+++ b/synapse/storage/registration.py
@@ -209,7 +209,7 @@ class RegistrationStore(background_updates.BackgroundUpdateStore):
                 " WHERE lower(name) = lower(?)"
             )
             txn.execute(sql, (user_id,))
-            return dict(txn.fetchall())
+            return dict(txn)
 
         return self.runInteraction("get_users_by_id_case_insensitive", f)
 
diff --git a/synapse/storage/room.py b/synapse/storage/room.py
index 8a2fe2fdf5..e4c56cc175 100644
--- a/synapse/storage/room.py
+++ b/synapse/storage/room.py
@@ -396,7 +396,7 @@ class RoomStore(SQLBaseStore):
                     sql % ("AND appservice_id IS NULL",),
                     (stream_id,)
                 )
-            return dict(txn.fetchall())
+            return dict(txn)
         else:
             # We want to get from all lists, so we need to aggregate the results
 
@@ -422,7 +422,7 @@ class RoomStore(SQLBaseStore):
 
             results = {}
             # A room is visible if its visible on any list.
-            for room_id, visibility in txn.fetchall():
+            for room_id, visibility in txn:
                 results[room_id] = bool(visibility) or results.get(room_id, False)
 
             return results
diff --git a/synapse/storage/signatures.py b/synapse/storage/signatures.py
index e1dca927d7..67d5d9969a 100644
--- a/synapse/storage/signatures.py
+++ b/synapse/storage/signatures.py
@@ -72,7 +72,7 @@ class SignatureStore(SQLBaseStore):
             " WHERE event_id = ?"
         )
         txn.execute(query, (event_id, ))
-        return {k: v for k, v in txn.fetchall()}
+        return {k: v for k, v in txn}
 
     def _store_event_reference_hashes_txn(self, txn, events):
         """Store a hash for a PDU
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index 1b42bea07a..e8bd02e773 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -373,10 +373,9 @@ class StateStore(SQLBaseStore):
                         " WHERE state_group = ? %s" % (where_clause,),
                         args
                     )
-                    rows = txn.fetchall()
                     results[group].update({
                         (typ, state_key): event_id
-                        for typ, state_key, event_id in rows
+                        for typ, state_key, event_id in txn
                         if (typ, state_key) not in results[group]
                     })
 
diff --git a/synapse/storage/tags.py b/synapse/storage/tags.py
index 5a2c1aa59b..bff73f3f04 100644
--- a/synapse/storage/tags.py
+++ b/synapse/storage/tags.py
@@ -95,7 +95,7 @@ class TagsStore(SQLBaseStore):
             for stream_id, user_id, room_id in tag_ids:
                 txn.execute(sql, (user_id, room_id))
                 tags = []
-                for tag, content in txn.fetchall():
+                for tag, content in txn:
                     tags.append(json.dumps(tag) + ":" + content)
                 tag_json = "{" + ",".join(tags) + "}"
                 results.append((stream_id, user_id, room_id, tag_json))
@@ -132,7 +132,7 @@ class TagsStore(SQLBaseStore):
                 " WHERE user_id = ? AND stream_id > ?"
             )
             txn.execute(sql, (user_id, stream_id))
-            room_ids = [row[0] for row in txn.fetchall()]
+            room_ids = [row[0] for row in txn]
             return room_ids
 
         changed = self._account_data_stream_cache.has_entity_changed(