ETS: update list value without race condition

Frank Muller frank.muller.erl@REDACTED
Thu Apr 22 13:32:12 CEST 2021

Hi guys

I’ve a little issue I’m unable to solve with the current ETS API.

My table is of type set. Keys are integers and values are list of names:
123 -> [ jane, john, bob ]
456 -> [ joe, alice ]

Process A with Key=123 wants to delete ‘Jane’ while process B with Key=123
wants to add ‘Adam’.

First, they both needs to read the value associated with Key=123, update
that list accordingly and set back the new value.

But this lead to race condition (ex. process B could put back ‘jane’ - last
write wins).

Could this problem be solved atomically without involving explicit locking
per Key?

Is there any other better way to represent this data set which will not
suffer from the race condition?

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