Describe the bug

A table with a key of type {map(), reference()} with multiple entries and one with the key contaiing an empty map can result in ets:select_replace when used with an empty map in the key replacing 2 instead of 1 object.

This doesn't always happen. It'll replace only the 1 object with key containing #{} in some tables, while others tables it'll replace 2. If no object as the key #{} then it'll never replace one of the other objects and if there are more than 2 objects it'll never replace more than 1 or 2. And if no object has #{} in the key it'll always replace 0. So there has to be one exactly equal key for it to replace any and with certain tables it'll replace 2 instead of 1.

Important to also note that it happens immediately when a tables with this behavior is used, so the example to reproduce does 1 select_replace but must do it hundreds of times on a new table each time in order to reproduce.

To Reproduce

Thanks to @max-au for creating a minimal example, https://gist.github.com/max-au/2d4bb71f2b41a93c465dce592a21e86d

Running this code will result in output like:

Iteration 95: replaced 2 entries. Before:
[{{#{key => value},#Ref<0.2679931898.3968073729.103219>},original},
 {{#{},#Ref<0.2679931898.3968073729.103219>},original}]

After:
[{{#{key => value},#Ref<0.2679931898.3968073729.103219>},new},
 {{#{},#Ref<0.2679931898.3968073729.103219>},new}]

** exception error: {[{{#{key => value},#Ref<0.2679931898.3968073729.103219>},
                       original},
                      {{#{},#Ref<0.2679931898.3968073729.103219>},original}],
                     {#{},#Ref<0.2679931898.3968073729.103219>}}

This shows that on the 95th new table both elements in the table were replaced, all 94 before it only replaced the 1 element.

Expected behavior

Only 1 element being replaced each time, the one with key {#{}, #Ref<...>}. But I could also see it being correct to replace all objects because #{} will match any map in a match, but not it sometimes 1, sometimes 2, sometimes 0 if no #{} exists in the table and never >2. And it should be consistent whether a reference is in the key or not.

Affected versions

I have tried this on OTP-24 and 27.0-rc2.

Additional context

This was found due to transient CI failures in the metrics testing of https://github.com/open-telemetry/opentelemetry-erlang. Sometimes a result in a float counter (which use select_replace to increment the counter) would be wrong.