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Fix rare deadlock when using read/write locks #16169
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reivilibre
approved these changes
Aug 23, 2023
| AND token = OLD.token | ||
| FOR UPDATE; | ||
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| IF NOT FOUND THEN |
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ooi: does still still work as expected with PERFORM?
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You make a good point there. I'll shove the returned row into a variable, as I can't see any obvious documentation
I haven't thought of a way of doing so :( I did try spawning and dropping lots of locks at once, but that didn't trigger the failure mode. |
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Turns out #16133 was incorrect, as the lock for the row being deleted is taken out before the trigger fires.
Let's revert that, and instead try and fix the race by only updating the
_modetable if the deleted row's token matches. This way when only one lock at a time will attempt to update the_modetable on deletion. Similarly for insertion.