Rename database classes to make some sense (#8033)

synapse/storage/databases/main/state_deltas.py

@@ -0,0 +1,121 @@
+# -*- coding: utf-8 -*-
+# Copyright 2018 Vector Creations Ltd
+#
+# 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.
+
+import logging
+
+from twisted.internet import defer
+
+from synapse.storage._base import SQLBaseStore
+
+logger = logging.getLogger(__name__)
+
+
+class StateDeltasStore(SQLBaseStore):
+    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:
+            - stream_id (int)
+            - room_id (str)
+            - type (str): event type
+            - state_key (str):
+            - event_id (str|None): new event_id for this state key. None if the
+                state has been deleted.
+            - prev_event_id (str|None): previous event_id for this state key. None
+                if it's new state.
+
+        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[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
+        ):
+            # 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 defer.succeed((max_stream_id, []))
+
+        def get_current_state_deltas_txn(txn):
+            # First we calculate the max stream id that will give us less than
+            # N results.
+            # We arbitarily limit to 100 stream_id entries to ensure we don't
+            # select toooo many.
+            sql = """
+                SELECT stream_id, count(*)
+                FROM current_state_delta_stream
+                WHERE stream_id > ? AND stream_id <= ?
+                GROUP BY stream_id
+                ORDER BY stream_id ASC
+                LIMIT 100
+            """
+            txn.execute(sql, (prev_stream_id, max_stream_id))
+
+            total = 0
+
+            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 = """
+                SELECT stream_id, room_id, type, state_key, event_id, prev_event_id
+                FROM current_state_delta_stream
+                WHERE ? < stream_id AND stream_id <= ?
+                ORDER BY stream_id ASC
+            """
+            txn.execute(sql, (prev_stream_id, clipped_stream_id))
+            return clipped_stream_id, self.db_pool.cursor_to_dict(txn)
+
+        return self.db_pool.runInteraction(
+            "get_current_state_deltas", get_current_state_deltas_txn
+        )
+
+    def _get_max_stream_id_in_current_state_deltas_txn(self, txn):
+        return self.db_pool.simple_select_one_onecol_txn(
+            txn,
+            table="current_state_delta_stream",
+            keyvalues={},
+            retcol="COALESCE(MAX(stream_id), -1)",
+        )
+
+    def get_max_stream_id_in_current_state_deltas(self):
+        return self.db_pool.runInteraction(
+            "get_max_stream_id_in_current_state_deltas",
+            self._get_max_stream_id_in_current_state_deltas_txn,
+        )