4 ms·

I am the author of the CT vector CRDT, also the author of the Replicated Object Notation http://github.com/gritzko/ron http://github.com/gritzko/ron. I tried t

I am the author of the CT vector CRDT, also the author of the Replicated Object Notation http://github.com/gritzko/ron http://github.com/gritzko/ron. I tried to look into the code, and I am not sure which way they implemented list and vector. The explanation is a bit confusing, especially the mention of "insertion index". Definition and support for Schism's Convergent List type. The convergent list is a simple timestamped log of entries with a vector clock. Convergence places entries into the resultant list In insertion order. The vector clock conveys that an item has been removed from the list on another node." Convergence places entries into the resultant vector in insertion order, with insertions occurring by replaying insertions operations in order. CRDT is all about partial orders, so what does it all mean? Orders are different for different replicas. (Disclaimer. I am not a Clojurist.)

dunham 8y ago
Yeah, I couldn't follow the descriptions either. It looks like "list" only supports appending (conj), removing the first item (rest), and removing all items (empty). The data consists of a list of items, a "clock" (map of nodeId to Date object), and a list of (nodeId,Date) corresponding to the values. I think they're using the clock to determine whether to drop deleted items on merge. Code for the operations is [list.cljc:153-169](https://github.com/aredington/schism/blob/master/src/schism/impl/types/list.cljc#L153-L169 https://github.com/aredington/schism/blob/master/src/schism/...). The merge code is "synchronize" a little further down (I didn't read through it). The "vector" object supports append (conj), pop, clearing the list (empty), and setting a value at a position (assoc). It does _not_ support insert/delete. It is structured similarly to "list" except using vectors instead of lists for the values and the timestamps. Code is at [vector.cljc:222-244](https://github.com/aredington/schism/blob/master/src/schism/impl/types/vector.cljc#L222-L244 https://github.com/aredington/schism/blob/master/src/schism/...)

dunham 8y ago

Yeah, I couldn't follow the descriptions either. It looks like "list" only supports appending (conj), removing the first item (rest), and removing all items (empty). The data consists of a list of items, a "clock" (map of nodeId to Date object), and a list of (nodeId,Date) corresponding to the values. I think they're using the clock to determine whether to drop deleted items on merge. Code for the operations is [list.cljc:153-169](https://github.com/aredington/schism/blob/master/src/schism/impl/types/list.cljc#L153-L169 https://github.com/aredington/schism/blob/master/src/schism/...). The merge code is "synchronize" a little further down (I didn't read through it). The "vector" object supports append (conj), pop, clearing the list (empty), and setting a value at a position (assoc). It does _not_ support insert/delete. It is structured similarly to "list" except using vectors instead of lists for the values and the timestamps. Code is at [vector.cljc:222-244](https://github.com/aredington/schism/blob/master/src/schism/impl/types/vector.cljc#L222-L244 https://github.com/aredington/schism/blob/master/src/schism/...)