I'm part of the way through. Here are some thoughts.
- Is there a way to materialize all of the past up to some point, throwing out history in the process, so as to reduce the overhead of CRDT?
- Some CRDT algorithms (really, representations of operations) are better at modeling a user's intent -- rather than "insert 'H' at 101, insert 'e' at 102, ..." and so on, it's "insert 'Hello' between ...". As I'm not familiar with OT, I wonder whether this begins to approach OT... In any case, some of the better CRDT algorithms for text editing tend to require more overhead, which is why the preceding thought.
- I'm much more interested in CRDTs for distributed relational databases, where it's much easier to reason about intent. "Relational" really means "has a well defined, enforced schema", while "text" means "anything goes" -- it's necessarily easier to reason about the former than the latter! Even so, a set of related updates to a relational database may be the complex result of a simpler abstraction -a simpler operation that the user intended- and eventual consistency semantics may ruin that result. One way to deal with that is to centralize certain kinds of operations, but those had better be less essential to business continuity.
- I'm with you on point #1. Obviously could be a source of good research, but also, it probably depends on policy. How many undos do you want to preserve? Even a one-headed VSCode instance only saves so many undos. You could probably hybrid CRDT with a consensus algorithm like raft to perform compactions.
Right, if it's about undo history, screw that, at some point you don't care anymore -- you might build a sort of VCS into the text editor so you can keep track of changes in a less granular way. If it's about knowing when you have all the history before some point in time, then that's doable.
