From 6c3ce7109b87670af158069da35ece71c2bbeb5a Mon Sep 17 00:00:00 2001
From: Kezhu Wang <kezhuw@gmail.com>
Date: Mon, 16 Sep 2024 15:41:19 +0800
Subject: [PATCH] Fix fence table not sorted after fencing non intersecting
 span

---
 src/tablet/concurrency/fence.rs | 32 ++++++++++++++++++++++++++------
 1 file changed, 26 insertions(+), 6 deletions(-)

diff --git a/src/tablet/concurrency/fence.rs b/src/tablet/concurrency/fence.rs
index 4f07a04..495af3c 100644
--- a/src/tablet/concurrency/fence.rs
+++ b/src/tablet/concurrency/fence.rs
@@ -14,6 +14,8 @@
 
 use std::cmp::Ordering::*;
 
+use tracing::trace;
+
 use crate::protos::{KeySpan, KeySpanRef, SpanOrdering, Timestamp, Uuid};
 
 #[derive(Debug, Clone, Copy)]
@@ -91,18 +93,14 @@ impl FenceTable {
         Barrier::new(Uuid::max(), self.closed_ts)
     }
 
-    /// Fences future writes to given span at or beneath given timestamp.
-    pub fn fence(&mut self, txn_id: Uuid, mut span: KeySpan, ts: Timestamp) {
-        if ts <= self.closed_ts {
-            return;
-        }
+    fn fence_internally(&mut self, txn_id: Uuid, mut span: KeySpan, ts: Timestamp) {
         let mut i = self.fences.partition_point(|fence| fence.span.is_before(&span.key));
         self.clear_closed_fences(i);
         while i < self.fences.len() {
             let fence = &mut self.fences[i];
             match span.as_ref().compare(fence.span.as_ref()) {
                 SpanOrdering::LessDisjoint | SpanOrdering::LessContiguous => {
-                    self.fences.push(Fence::new(span, txn_id, ts));
+                    self.fences.insert(i, Fence::new(span, txn_id, ts));
                     return;
                 },
                 SpanOrdering::GreaterDisjoint | SpanOrdering::GreaterContiguous => unreachable!(),
@@ -188,6 +186,26 @@ impl FenceTable {
         }
     }
 
+    /// Fences future writes to given span at or beneath given timestamp.
+    pub fn fence(&mut self, txn_id: Uuid, span: KeySpan, ts: Timestamp) {
+        trace!("fence txn {}, span {:?}, ts {}, closed_ts {}", txn_id, span, ts, self.closed_ts);
+        if ts <= self.closed_ts {
+            return;
+        }
+        self.fence_internally(txn_id, span, ts);
+        debug_assert!({
+            for i in 0..self.fences.len() - 1 {
+                let before = &self.fences[i];
+                let after = &self.fences[i + 1];
+                match before.span.as_ref().compare(after.span.as_ref()) {
+                    SpanOrdering::LessDisjoint | SpanOrdering::LessContiguous => {},
+                    _ => panic!("fence table at position {i} is not ordered. {self:?}"),
+                }
+            }
+            true
+        });
+    }
+
     pub fn min_write_ts(&mut self, txn_id: Uuid, writes: &[KeySpan], mut ts: Timestamp) -> Timestamp {
         for write in writes {
             let barrier = self.max_barrier(write.as_ref());
@@ -367,5 +385,7 @@ mod tests {
         assert_that!(fences.min_write_ts(txn1, &[KeySpan::new_range(b"k16", b"k21")], ts70)).is_equal_to(ts70.next());
         assert_that!(fences.min_write_ts(txn2, &[KeySpan::new_range(b"k16", b"k21")], ts70)).is_equal_to(ts70.next());
         assert_that!(fences.min_write_ts(txn3, &[KeySpan::new_range(b"k16", b"k21")], ts70)).is_equal_to(ts70.next());
+
+        fences.fence(Uuid::nil(), KeySpan::new_range("k19", "k20"), ts70);
     }
 }