From 934b0fdda91f55709a41ae5cbf1335059429648e Mon Sep 17 00:00:00 2001
From: Zixuan Chen <remch183@outlook.com>
Date: Wed, 9 Nov 2022 14:11:06 +0800
Subject: [PATCH] perf: speed up find path and common ancestors

---
 crates/loro-core/examples/text_sync.rs | 46 ++++++++++++++------------
 crates/loro-core/src/dag.rs            | 23 +++++++++++++
 2 files changed, 47 insertions(+), 22 deletions(-)

diff --git a/crates/loro-core/examples/text_sync.rs b/crates/loro-core/examples/text_sync.rs
index afc6c7ba..4bd82a74 100644
--- a/crates/loro-core/examples/text_sync.rs
+++ b/crates/loro-core/examples/text_sync.rs
@@ -20,29 +20,31 @@ fn main() {
     let mut loro = LoroCore::default();
     let mut loro_b = LoroCore::default();
     let start = Instant::now();
-    for txn in txns.unwrap().as_array().unwrap() {
-        let mut text = loro.get_or_create_root_text("text").unwrap();
-        let patches = txn
-            .as_object()
-            .unwrap()
-            .get("patches")
-            .unwrap()
-            .as_array()
-            .unwrap();
-        for patch in patches {
-            let pos = patch[0].as_u64().unwrap() as usize;
-            let del_here = patch[1].as_u64().unwrap() as usize;
-            let ins_content = patch[2].as_str().unwrap();
-            text.delete(pos, del_here);
-            text.insert(pos, ins_content);
-        }
+    for _ in 0..10 {
+        for txn in txns.unwrap().as_array().unwrap() {
+            let mut text = loro.get_or_create_root_text("text").unwrap();
+            let patches = txn
+                .as_object()
+                .unwrap()
+                .get("patches")
+                .unwrap()
+                .as_array()
+                .unwrap();
+            for patch in patches {
+                let pos = patch[0].as_u64().unwrap() as usize;
+                let del_here = patch[1].as_u64().unwrap() as usize;
+                let ins_content = patch[2].as_str().unwrap();
+                text.delete(pos, del_here);
+                text.insert(pos, ins_content);
+            }
 
-        let a = text.text_len();
-        drop(text);
-        loro_b.import(loro.export(loro_b.vv()));
-        let text = loro_b.get_or_create_root_text("text").unwrap();
-        let b = text.text_len();
-        assert_eq!(a, b);
+            let a = text.text_len();
+            drop(text);
+            loro_b.import(loro.export(loro_b.vv()));
+            let text = loro_b.get_or_create_root_text("text").unwrap();
+            let b = text.text_len();
+            assert_eq!(a, b);
+        }
     }
     loro_b.debug_inspect();
     loro.debug_inspect();
diff --git a/crates/loro-core/src/dag.rs b/crates/loro-core/src/dag.rs
index 6645889a..f715ec71 100644
--- a/crates/loro-core/src/dag.rs
+++ b/crates/loro-core/src/dag.rs
@@ -117,6 +117,21 @@ impl<T: Dag + ?Sized> DagUtils for T {
             if from.client_id == to.client_id {
                 let from_span = self.get(from).unwrap();
                 let to_span = self.get(to).unwrap();
+                if std::ptr::eq(from_span, to_span) {
+                    if from.counter < to.counter {
+                        ans.right.insert(
+                            from.client_id,
+                            CounterSpan::new(from.counter + 1, to.counter + 1),
+                        );
+                    } else {
+                        ans.left.insert(
+                            from.client_id,
+                            CounterSpan::new(to.counter + 1, from.counter + 1),
+                        );
+                    }
+                    return ans;
+                }
+
                 if from_span.deps().len() == 1 && to_span.contains_id(from_span.deps()[0]) {
                     ans.left.insert(
                         from.client_id,
@@ -533,6 +548,14 @@ where
         if left.client_id == right.client_id {
             let left_span = get(left).unwrap();
             let right_span = get(right).unwrap();
+            if std::ptr::eq(left_span, right_span) {
+                if left.counter < right.counter {
+                    return smallvec![left];
+                } else {
+                    return smallvec![right];
+                }
+            }
+
             if left_span.deps().len() == 1 && right_span.contains_id(left_span.deps()[0]) {
                 return smallvec![right];
             }