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169a8a66f2
This class exists for one purpose only: to serve as glue code between dht::ring_position and boost::icl::interval_map. The latter requires that keys in its intervals are: * default constructible * copyable * have standalone compare operations For this reason we have to wrap `dht::ring_position` in a class, together with a schema to provide all this. This is `compatible_ring_position`. There is one further requirement by code using the interval map: it wants to do lookups without copying the lookup key(s). To solve this, we came up with `compatible_ring_position_or_view` which is a union of a key or a key view + schema. As we recently found out, boost::icl copies its keys **a lot**. It seems to assume these keys are cheap to copy and carelessly copies them around even when iterating over the map. But `compatible_ring_position_or_view` is not cheap to copy as it copies a `dht::ring_position` which allocates, and it does that via an `std::optional` and `std::variant` to add insult to injury. This patch make said class cheap to copy, by getting rid of the variant and storing the `dht::ring_position` via a shared pointer. The view is stored separately and either points to the ring position stored in the shared pointer or to an outside ring position (for lookups). Fixes: #11669 Closes #11670