Keys with lists of fields make values of all those fields go into the same single index

[mscott]

[18:46] pobrien: I've got an entity for electrical connectors that are mated - and if a connector is mated, it can only mate to one other connector
[18:46] pobrien:     _key(connector_a, connector_b)
[18:46] pobrien:     _index(connector_a)
[18:46] pobrien:     _index(connector_b)
[18:47] pobrien: but this doesn't quite cut it, since it doesn't keep connector "Foo" from appearing in two pairs: ("Foo", "Bar") and ("Baz", "Foo")
[18:47] pobrien: what would be cool is to be able to say:  _key([connector_a, connector_b])
[18:48] pobrien: if a key is a list of fields, then the values from all fields in the list go into the same, single, index
[18:49] pobrien: just something to think about