From 0c9fbce63ae6e2c54f73c9ea8c0c4101a48c42c5 Mon Sep 17 00:00:00 2001
From: Petros Angelatos <petrosagg@gmail.com>
Date: Thu, 9 Mar 2023 21:54:25 +0100
Subject: [PATCH] session: only clone timestamps when needed

In microbenchmarks (see https://github.com/MaterializeInc/materialize/pull/17998#discussion_r1131583050)
the code in the PR performed better than the current version.

Signed-off-by: Petros Angelatos <petrosagg@gmail.com>
---
 timely/src/dataflow/channels/pushers/buffer.rs | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/timely/src/dataflow/channels/pushers/buffer.rs b/timely/src/dataflow/channels/pushers/buffer.rs
index 6f92dabb0..841bce02f 100644
--- a/timely/src/dataflow/channels/pushers/buffer.rs
+++ b/timely/src/dataflow/channels/pushers/buffer.rs
@@ -36,8 +36,13 @@ impl<T, C: Container, P: Push<BundleCore<T, C>>> BufferCore<T, C, P> where T: Eq
 
     /// Returns a `Session`, which accepts data to send at the associated time
     pub fn session(&mut self, time: &T) -> Session<T, C, P> {
-        if let Some(true) = self.time.as_ref().map(|x| x != time) { self.flush(); }
-        self.time = Some(time.clone());
+        match self.time {
+            Some(ref t) => if t != time {
+                self.flush();
+                self.time = Some(time.clone())
+            },
+            None => self.time = Some(time.clone()),
+        };
         Session { buffer: self }
     }
     /// Allocates a new `AutoflushSession` which flushes itself on drop.