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What does no merge conflicts to resolve even mean? Isn’t it fundamentally impossible to have both no merge conflicts and have meaningful data. Incase of a conf

by nojvek 6y ago

What does no merge conflicts to resolve even mean? Isn’t it fundamentally impossible to have both no merge conflicts and have meaningful data. Incase of a conflict you can either keep the most recent change or both changes. But like got keeps both changes with <<<< HEAD and theirs markers the code is now invalid and won’t compile. Suppose both the changes were kept without conflict resolution, now you have two things that may interfere with each other. I’ve had git mess up by trying to do an auto merge and still breaking the logic. So I don’t think there is a golden algorithms. Just a bunch of trade offs like any other problem.

liuliu 6y ago
The talk makes it clear, "no conflict" in CRDT sense is that states update, even ordered differently will converge to the same state. For practical sense, it is last-write-win baked in the the CRDT design (you can choose alternatives, but it has to be in the CRDT design, not something pluggable).
butterisgood 6y ago
If the merge operation is commutative the order doesn’t matter.
- ulrikrasmussen 6y ago
  Yes, but the question is whether the semantics is meaningful for the application (e.g. text editing). I can also make string concatenation commutative by generalizing the concept of strings to multisets, but it is not given that this structure is useful for the applications where strings are needed.
  - sitkack 6y ago
    > Yes, but the question is whether the semantics is meaningful for the application (e.g. text editing). CRDTs are building blocks for larger systems. They themselves need to be composed into higher level constructs. I think this is the crux of the CRDT, it assists the application designer in creating an algebra over the domain model such that state can get updated w/o having a single representation of that state space. It pushes that complexity back down, so that we can reason about it in serial code.

by nojvek 6y ago

liuliu 6y ago

The talk makes it clear, "no conflict" in CRDT sense is that states update, even ordered differently will converge to the same state. For practical sense, it is last-write-win baked in the the CRDT design (you can choose alternatives, but it has to be in the CRDT design, not something pluggable).

butterisgood 6y ago

If the merge operation is commutative the order doesn’t matter.

ulrikrasmussen 6y ago
Yes, but the question is whether the semantics is meaningful for the application (e.g. text editing). I can also make string concatenation commutative by generalizing the concept of strings to multisets, but it is not given that this structure is useful for the applications where strings are needed.
- sitkack 6y ago
  > Yes, but the question is whether the semantics is meaningful for the application (e.g. text editing). CRDTs are building blocks for larger systems. They themselves need to be composed into higher level constructs. I think this is the crux of the CRDT, it assists the application designer in creating an algebra over the domain model such that state can get updated w/o having a single representation of that state space. It pushes that complexity back down, so that we can reason about it in serial code.