unloadRecord destroys manyArray

[hjdivad]

see https://github.com/emberjs/data/blob/master/addon/-private/system/relationships/state/has-many.js#L59-L65

presumably the right behaviour is to issue a change event for that index and then call it a day.

cc @stefanpenner @igorT

[BryanCrotaz]

surely the many array is the bit that's using RAM so we do want to destroy it on unload?

[stefanpenner]

@BryanCrotaz I believe in this case when a single belongsTo is unloaded, it destroys any hasMany pointing to it, forcing it to be invalidated and totally rebuilt when accessed.

[BryanCrotaz]

Ah that's a Bad Thing.

[BryanCrotaz]

although when the last belongsTo is unloaded, this should happen

[stefanpenner]

@BryanCrotaz well it should become empty, but the hasMany should stick around until it's record is unloaded/destroyed

[runspired]

This was resolved by #5273 and other more recent fixes to the relationship layer.