diff --git a/synapse/storage/databases/main/roommember.py b/synapse/storage/databases/main/roommember.py
index dfa7dd48d9..b8c78baa6c 100644
--- a/synapse/storage/databases/main/roommember.py
+++ b/synapse/storage/databases/main/roommember.py
@@ -1693,93 +1693,6 @@ class RoomMemberBackgroundUpdateStore(SQLBaseStore):
columns=["user_id", "room_id"],
)
- self.db_pool.updates.register_background_update_handler(
- "populate_participant_bg_update", self._populate_participant
- )
-
- async def _populate_participant(self, progress: JsonDict, batch_size: int) -> int:
- """
- Background update to populate column `participant` on `room_memberships` table
-
- A 'participant' is someone who is currently joined to a room and has sent at least
- one `m.room.message` or `m.room.encrypted` event.
-
- This background update will set the `participant` column across all rows in
- `room_memberships` based on the user's *current* join status, and if
- they've *ever* sent a message or encrypted event. Therefore one should
- never assume the `participant` column's value is based solely on whether
- the user participated in a previous "session" (where a "session" is defined
- as a period between the user joining and leaving). See
- https://github.com/element-hq/synapse/pull/18068#discussion_r1931070291
- for further detail.
- """
- stream_token = progress.get("last_stream_token", None)
-
- def _get_max_stream_token_txn(txn: LoggingTransaction) -> int:
- sql = """
- SELECT event_stream_ordering from room_memberships
- ORDER BY event_stream_ordering DESC
- LIMIT 1;
- """
- txn.execute(sql)
- res = txn.fetchone()
- if not res or not res[0]:
- return 0
- return res[0]
-
- def _background_populate_participant_txn(
- txn: LoggingTransaction, stream_token: str
- ) -> None:
- sql = """
- UPDATE room_memberships
- SET participant = True
- FROM (
- SELECT DISTINCT c.state_key, e.room_id
- FROM current_state_events AS c
- INNER JOIN events AS e ON c.room_id = e.room_id
- WHERE c.membership = 'join'
- AND c.state_key = e.sender
- AND (
- e.type = 'm.room.message'
- OR e.type = 'm.room.encrypted'
- )
- ) AS subquery
- WHERE room_memberships.user_id = subquery.state_key
- AND room_memberships.room_id = subquery.room_id
- AND room_memberships.event_stream_ordering <= ?
- AND room_memberships.event_stream_ordering > ?;
- """
- batch = int(stream_token) - _POPULATE_PARTICIPANT_BG_UPDATE_BATCH_SIZE
- txn.execute(sql, (stream_token, batch))
-
- if stream_token is None:
- stream_token = await self.db_pool.runInteraction(
- "_get_max_stream_token", _get_max_stream_token_txn
- )
-
- if stream_token < 0:
- await self.db_pool.updates._end_background_update(
- "populate_participant_bg_update"
- )
- return _POPULATE_PARTICIPANT_BG_UPDATE_BATCH_SIZE
-
- await self.db_pool.runInteraction(
- "_background_populate_participant_txn",
- _background_populate_participant_txn,
- stream_token,
- )
-
- progress["last_stream_token"] = (
- stream_token - _POPULATE_PARTICIPANT_BG_UPDATE_BATCH_SIZE
- )
- await self.db_pool.runInteraction(
- "populate_participant_bg_update",
- self.db_pool.updates._background_update_progress_txn,
- "populate_participant_bg_update",
- progress,
- )
- return _POPULATE_PARTICIPANT_BG_UPDATE_BATCH_SIZE
-
async def _background_add_membership_profile(
self, progress: JsonDict, batch_size: int
) -> int:
diff --git a/synapse/storage/schema/main/delta/90/01_add_column_participant_room_memberships_table.sql b/synapse/storage/schema/main/delta/90/01_add_column_participant_room_memberships_table.sql
index 672be1031e..dafd046499 100644
--- a/synapse/storage/schema/main/delta/90/01_add_column_participant_room_memberships_table.sql
+++ b/synapse/storage/schema/main/delta/90/01_add_column_participant_room_memberships_table.sql
@@ -13,8 +13,4 @@
-- Add a column `participant` to `room_memberships` table to track whether a room member has sent
-- a `m.room.message` or `m.room.encrypted` event into a room they are a member of
-ALTER TABLE room_memberships ADD COLUMN participant BOOLEAN DEFAULT FALSE;
-
--- Add a background update to populate `participant` column
-INSERT INTO background_updates (ordering, update_name, progress_json) VALUES
- (9001, 'populate_participant_bg_update', '{}');
\ No newline at end of file
+ALTER TABLE room_memberships ADD COLUMN participant BOOLEAN DEFAULT FALSE;
\ No newline at end of file
diff --git a/synapse/storage/schema/main/delta/92/02_remove_populate_participant_bg_update.sql b/synapse/storage/schema/main/delta/92/02_remove_populate_participant_bg_update.sql
new file mode 100644
index 0000000000..e1f377c37d
--- /dev/null
+++ b/synapse/storage/schema/main/delta/92/02_remove_populate_participant_bg_update.sql
@@ -0,0 +1,17 @@
+--
+-- This file is licensed under the Affero General Public License (AGPL) version 3.
+--
+-- Copyright (C) 2025 New Vector, Ltd
+--
+-- This program is free software: you can redistribute it and/or modify
+-- it under the terms of the GNU Affero General Public License as
+-- published by the Free Software Foundation, either version 3 of the
+-- License, or (at your option) any later version.
+--
+-- See the GNU Affero General Public License for more details:
+-- <https://www.gnu.org/licenses/agpl-3.0.html>.
+
+-- Remove the background update if it was scheduled, as it is not rollback-safe
+-- See https://github.com/element-hq/synapse/issues/18356 for context
+DELETE FROM background_updates
+WHERE update_name = 'populate_participant_bg_update';
\ No newline at end of file
|
