forked-synapse/synapse/storage/schema/main/delta/79/05_read_write_locks_triggers.sql.postgres

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/* Copyright 2023 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.
*/
-- Fix up the triggers that were in `78/04_read_write_locks_triggers.sql`
-- Add a trigger to UPSERT into `worker_read_write_locks_mode` whenever we try
-- and acquire a lock, i.e. insert into `worker_read_write_locks`,
CREATE OR REPLACE FUNCTION upsert_read_write_lock_parent() RETURNS trigger AS $$
BEGIN
INSERT INTO worker_read_write_locks_mode (lock_name, lock_key, write_lock, token)
VALUES (NEW.lock_name, NEW.lock_key, NEW.write_lock, NEW.token)
ON CONFLICT (lock_name, lock_key)
DO UPDATE SET write_lock = NEW.write_lock, token = NEW.token;
RETURN NEW;
END
$$
LANGUAGE plpgsql;
DROP TRIGGER IF EXISTS upsert_read_write_lock_parent_trigger ON worker_read_write_locks;
CREATE TRIGGER upsert_read_write_lock_parent_trigger BEFORE INSERT ON worker_read_write_locks
FOR EACH ROW
EXECUTE PROCEDURE upsert_read_write_lock_parent();
-- Ensure that we keep `worker_read_write_locks_mode` up to date whenever a lock
-- is released (i.e. a row deleted from `worker_read_write_locks`). Either we
-- update the `worker_read_write_locks_mode.token` to match another instance
-- that has currently acquired the lock, or we delete the row if nobody has
-- currently acquired a lock.
CREATE OR REPLACE FUNCTION delete_read_write_lock_parent() RETURNS trigger AS $$
DECLARE
new_token TEXT;
BEGIN
SELECT token INTO new_token FROM worker_read_write_locks
WHERE
lock_name = OLD.lock_name
AND lock_key = OLD.lock_key
LIMIT 1 FOR UPDATE;
IF NOT FOUND THEN
DELETE FROM worker_read_write_locks_mode
WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key AND token = OLD.token;
ELSE
UPDATE worker_read_write_locks_mode
SET token = new_token
WHERE lock_name = OLD.lock_name AND lock_key = OLD.lock_key;
END IF;
RETURN NEW;
END
$$
LANGUAGE plpgsql;
DROP TRIGGER IF EXISTS delete_read_write_lock_parent_trigger ON worker_read_write_locks;
CREATE TRIGGER delete_read_write_lock_parent_trigger AFTER DELETE ON worker_read_write_locks
FOR EACH ROW
EXECUTE PROCEDURE delete_read_write_lock_parent();