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Reduce DB contention on worker locks #16160
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reivilibre
approved these changes
Aug 23, 2023
| 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 | ||
| WHERE OLD.write_lock != NEW.write_lock; |
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I thought it worthwhile to check the semantics of the WHERE here to ensure they still create the row lock:
Only rows for which this expression returns true will be updated, although all rows will be locked when the ON CONFLICT DO UPDATE action is taken.
— Postgres manual
Seems fine then
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We used to upsert the
tokenevery time we took out the lock. Instead, we only update an existing value when we have a conflictingwrite_lockvalue (which will then fail the foreign key constraint).