feat: add with fractional index config (#442)

* feat: add `with_fractional_index` config

* fix: share config state

Cargo.lock

@@ -1349,6 +1349,7 @@ dependencies = [
  "criterion 0.5.1",
  "fractional_index",
  "imbl",
+ "once_cell",
  "rand",
  "serde",
  "smallvec",

crates/fractional_index/Cargo.toml

@@ -16,6 +16,7 @@ imbl = "^3.0"
 smallvec = { workspace = true }
 serde = { workspace = true, features = ["derive", "rc"], optional = true }
 rand = { version = "^0.8" }
+once_cell = { workspace = true }
 
 [dev-dependencies]
 fraction_index = { version = "^2.0", package = "fractional_index" }

crates/fractional_index/src/lib.rs

@@ -9,6 +9,8 @@ use serde::{Deserialize, Serialize};
 mod jitter;
 
 const TERMINATOR: u8 = 128;
+static DEFAULT_FRACTIONAL_INDEX: once_cell::sync::Lazy<FractionalIndex> =
+    once_cell::sync::Lazy::new(|| FractionalIndex(Arc::new(vec![TERMINATOR])));
 
 #[derive(Debug, Clone, PartialEq, PartialOrd, Eq, Ord, Hash)]
 #[cfg_attr(feature = "serde", derive(Serialize, Deserialize))]
@@ -16,7 +18,7 @@ pub struct FractionalIndex(Arc<Vec<u8>>);
 
 impl Default for FractionalIndex {
     fn default() -> Self {
-        FractionalIndex(Arc::new(vec![TERMINATOR]))
+        DEFAULT_FRACTIONAL_INDEX.clone()
     }
 }
 

crates/fuzz/src/actor.rs

@@ -24,6 +24,8 @@ use super::{
     container::MapActor,
 };
 
+const DEFAULT_WITH_FRACTIONAL_INDEX: bool = false;
+
 #[derive(Debug)]
 pub struct Undo {
     pub undo: UndoManager,
@@ -45,6 +47,7 @@ impl Actor {
     pub fn new(id: PeerID) -> Self {
         let loro = LoroDoc::new();
         loro.set_peer_id(id).unwrap();
+        loro.set_with_fractional_index(DEFAULT_WITH_FRACTIONAL_INDEX);
         let undo = UndoManager::new(&loro);
         let tracker = Arc::new(Mutex::new(ContainerTracker::Map(MapTracker::empty(
             ContainerID::new_root("sys:root", ContainerType::Map),

crates/fuzz/src/container/map.rs

@@ -7,7 +7,7 @@ use loro::{Container, ContainerID, ContainerType, LoroDoc, LoroMap, LoroValue};
 
 use crate::{
     actions::{Actionable, FromGenericAction, GenericAction},
-    actor::{ActionExecutor, ActorTrait},
+    actor::{assert_value_eq, ActionExecutor, ActorTrait},
     crdt_fuzzer::FuzzValue,
     value::{ApplyDiff, ContainerTracker, MapTracker, Value},
 };
@@ -66,7 +66,11 @@ impl ActorTrait for MapActor {
         let map = self.loro.get_map("map");
         let value_a = map.get_deep_value();
         let value_b = self.tracker.lock().unwrap().to_value();
-        assert_eq!(&value_a, value_b.into_map().unwrap().get("map").unwrap());
+        assert_value_eq(
+            &value_a,
+            value_b.into_map().unwrap().get("map").unwrap(),
+            None,
+        );
     }
 
     fn container_len(&self) -> u8 {

crates/fuzz/src/container/tree.rs

@@ -14,7 +14,7 @@ use tracing::{debug, trace};
 
 use crate::{
     actions::{Actionable, FromGenericAction, GenericAction},
-    actor::{ActionExecutor, ActorTrait},
+    actor::{assert_value_eq, ActionExecutor, ActorTrait},
     crdt_fuzzer::FuzzValue,
     value::{ApplyDiff, ContainerTracker, MapTracker, Value},
 };
@@ -135,7 +135,11 @@ impl ActorTrait for TreeActor {
         let tree = loro.get_tree("tree");
         let result = tree.get_value_with_meta();
         let tracker = self.tracker.lock().unwrap().to_value();
-        assert_eq!(&result, tracker.into_map().unwrap().get("tree").unwrap());
+        assert_value_eq(
+            &result,
+            tracker.into_map().unwrap().get("tree").unwrap(),
+            None,
+        );
     }
 
     fn add_new_container(&mut self, container: Container) {

crates/loro-internal/src/configure.rs

@@ -5,6 +5,9 @@ pub struct Configure {
     pub(crate) text_style_config: Arc<RwLock<StyleConfigMap>>,
     record_timestamp: Arc<AtomicBool>,
     pub(crate) merge_interval: Arc<AtomicI64>,
+    /// Whether the tree has fractional index. `false` by default. If false, the fractional index is always [`FractionalIndex::default`] and
+    /// `tree_position_jitter` is not used.
+    pub(crate) tree_with_fractional_index: Arc<AtomicBool>,
     /// do not use `jitter` by default
     pub(crate) tree_position_jitter: Arc<AtomicU8>,
 }
@@ -16,6 +19,7 @@ impl Default for Configure {
             record_timestamp: Arc::new(AtomicBool::new(false)),
             merge_interval: Arc::new(AtomicI64::new(1000 * 1000)),
             tree_position_jitter: Arc::new(AtomicU8::new(0)),
+            tree_with_fractional_index: Arc::new(AtomicBool::new(false)),
         }
     }
 }
@@ -38,6 +42,10 @@ impl Configure {
                 self.tree_position_jitter
                     .load(std::sync::atomic::Ordering::Relaxed),
             )),
+            tree_with_fractional_index: Arc::new(AtomicBool::new(
+                self.tree_with_fractional_index
+                    .load(std::sync::atomic::Ordering::Relaxed),
+            )),
         }
     }
 
@@ -55,6 +63,11 @@ impl Configure {
             .store(record, std::sync::atomic::Ordering::Relaxed);
     }
 
+    pub fn set_with_fractional_index(&self, with_fractional_index: bool) {
+        self.tree_with_fractional_index
+            .store(with_fractional_index, std::sync::atomic::Ordering::Relaxed);
+    }
+
     pub fn set_fractional_index_jitter(&self, jitter: u8) {
         self.tree_position_jitter
             .store(jitter, std::sync::atomic::Ordering::Relaxed);

crates/loro-internal/src/handler/tree.rs

@@ -210,7 +210,6 @@ impl HandlerTrait for TreeHandler {
         self.inner.attached_handler()
     }
 
-    // TODO:
     fn get_value(&self) -> LoroValue {
         match &self.inner {
             MaybeDetached::Detached(t) => {

crates/loro-internal/src/loro.rs

@@ -173,6 +173,12 @@ impl LoroDoc {
         self.config.set_merge_interval(interval);
     }
 
+    /// Set whether to use fractional index for Tree Position.
+    #[inline]
+    pub fn set_with_fractional_index(&self, with_fractional_index: bool) {
+        self.config.set_with_fractional_index(with_fractional_index);
+    }
+
     /// Set the jitter of the tree position(Fractional Index).
     ///
     /// The jitter is used to avoid conflicts when multiple users are creating the node at the same position.

crates/loro-internal/src/state.rs

@@ -3,7 +3,7 @@ use std::{
     collections::BTreeMap,
     io::Write,
     sync::{
-        atomic::{AtomicU64, AtomicU8, Ordering},
+        atomic::{AtomicBool, AtomicU64, AtomicU8, Ordering},
         Arc, Mutex, RwLock, Weak,
     },
 };
@@ -310,8 +310,18 @@ impl State {
         Self::RichtextState(Box::new(RichtextState::new(idx, config)))
     }
 
-    pub fn new_tree(idx: ContainerIdx, peer: PeerID, jitter: Arc<AtomicU8>) -> Self {
-        Self::TreeState(Box::new(TreeState::new(idx, peer, jitter)))
+    pub fn new_tree(
+        idx: ContainerIdx,
+        peer: PeerID,
+        jitter: Arc<AtomicU8>,
+        with_fractional_index: Arc<AtomicBool>,
+    ) -> Self {
+        Self::TreeState(Box::new(TreeState::new(
+            idx,
+            peer,
+            jitter,
+            with_fractional_index,
+        )))
     }
 
     pub fn new_unknown(idx: ContainerIdx) -> Self {
@@ -1476,6 +1486,7 @@ fn create_state_(idx: ContainerIdx, config: &Configure, peer: u64) -> State {
             idx,
             peer,
             config.tree_position_jitter.clone(),
+            config.tree_with_fractional_index.clone(),
         ))),
         ContainerType::MovableList => State::MovableListState(Box::new(MovableListState::new(idx))),
         #[cfg(feature = "counter")]

crates/loro-internal/src/state/tree_state.rs

@@ -13,7 +13,7 @@ use serde::Serialize;
 use std::collections::VecDeque;
 use std::fmt::Debug;
 use std::ops::{Deref, DerefMut};
-use std::sync::atomic::{AtomicU8, Ordering};
+use std::sync::atomic::{AtomicBool, AtomicU8, Ordering};
 use std::sync::{Arc, Mutex, Weak};
 
 use super::{ContainerState, DiffApplyContext};
@@ -41,8 +41,10 @@ pub struct TreeState {
     idx: ContainerIdx,
     trees: FxHashMap<TreeID, TreeStateNode>,
     children: TreeChildrenCache,
+    /// Whether the tree has fractional index. If false, the fractional index is always [`FractionalIndex::default`]
+    with_fractional_index: Arc<AtomicBool>,
     rng: Option<rand::rngs::StdRng>,
-    jitter: u8,
+    jitter: Arc<AtomicU8>,
 }
 
 #[derive(Debug, Clone, PartialEq, Eq)]
@@ -597,16 +599,22 @@ impl NodePosition {
 }
 
 impl TreeState {
-    pub fn new(idx: ContainerIdx, peer_id: PeerID, config: Arc<AtomicU8>) -> Self {
-        let jitter = config.load(Ordering::Relaxed);
+    pub fn new(
+        idx: ContainerIdx,
+        peer_id: PeerID,
+        jitter_config: Arc<AtomicU8>,
+        with_fractional_index: Arc<AtomicBool>,
+    ) -> Self {
+        let jitter = jitter_config.load(Ordering::Relaxed);
         let use_jitter = jitter != 1;
 
         Self {
             idx,
             trees: FxHashMap::default(),
             children: Default::default(),
+            with_fractional_index,
             rng: use_jitter.then_some(rand::rngs::StdRng::seed_from_u64(peer_id)),
-            jitter,
+            jitter: jitter_config,
         }
     }
 
@@ -677,10 +685,6 @@ impl TreeState {
         !self.is_node_deleted(&target)
     }
 
-    pub fn contains_internal(&self, target: &TreeID) -> bool {
-        self.trees.contains_key(target)
-    }
-
     /// Get the parent of the node, if the node is deleted or does not exist, return None
     pub fn parent(&self, target: &TreeID) -> TreeParentId {
         self.trees
@@ -823,11 +827,15 @@ impl TreeState {
         parent: &TreeParentId,
         index: usize,
     ) -> FractionalIndexGenResult {
+        if !self.with_fractional_index.load(Ordering::Relaxed) {
+            return FractionalIndexGenResult::Ok(FractionalIndex::default());
+        }
+
         if let Some(rng) = self.rng.as_mut() {
             self.children
                 .entry(*parent)
                 .or_default()
-                .generate_fi_at_jitter(index, target, rng, self.jitter)
+                .generate_fi_at_jitter(index, target, rng, self.jitter.load(Ordering::Relaxed))
         } else {
             self.children
                 .entry(*parent)
@@ -936,8 +944,7 @@ impl ContainerState for TreeState {
                                         });
                                     }
                                     // Otherwise, it's a normal move inside deleted nodes, no event is needed
-                                } else {
-                                    if was_alive {
+                                } else if was_alive {
                                     // normal move
                                     ans.push(TreeDiffItem {
                                         target,
@@ -959,7 +966,6 @@ impl ContainerState for TreeState {
                                     });
                                 }
                             }
-                            }
                         } else {
                             self.mov(target, *parent, last_move_op, Some(position.clone()), false)
                                 .unwrap();
@@ -1490,8 +1496,12 @@ mod snapshot {
                 peers.push(PeerID::from_le_bytes(buf));
             }
 
-            let mut tree =
-                TreeState::new(idx, ctx.peer, ctx.configure.tree_position_jitter.clone());
+            let mut tree = TreeState::new(
+                idx,
+                ctx.peer,
+                ctx.configure.tree_position_jitter.clone(),
+                ctx.configure.tree_with_fractional_index.clone(),
+            );
             let encoded: EncodedTree = serde_columnar::from_bytes(bytes)?;
             let fractional_indexes = PositionArena::decode(&encoded.fractional_indexes).unwrap();
             let fractional_indexes = fractional_indexes.parse_to_positions();

crates/loro/src/lib.rs

@@ -155,6 +155,12 @@ impl LoroDoc {
         self.doc.set_change_merge_interval(interval);
     }
 
+    /// Set whether to use fractional index for Tree Position.
+    #[inline]
+    pub fn set_with_fractional_index(&self, with_fractional_index: bool) {
+        self.doc.set_with_fractional_index(with_fractional_index);
+    }
+
     /// Set the jitter of the tree position(Fractional Index).
     ///
     /// The jitter is used to avoid conflicts when multiple users are creating the node at the same position.