From 34b0736f2c5f4f7f3238da5be044be173b776921 Mon Sep 17 00:00:00 2001
From: Ajit Yagaty <ajityagaty@gmail.com>
Date: Wed, 11 May 2016 00:51:00 -0700
Subject: [PATCH] mvcc: Reduce number of allocs when watchableStore if no
 watchers.

When there are no watchers the number of allocations made while handling
a PUT operation can be reduced by exiting early.
---
 mvcc/watcher_group.go | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/mvcc/watcher_group.go b/mvcc/watcher_group.go
index 4b654b751..4394f8ee0 100644
--- a/mvcc/watcher_group.go
+++ b/mvcc/watcher_group.go
@@ -83,6 +83,10 @@ func (wb watcherBatch) contains(w *watcher) bool {
 // newWatcherBatch maps watchers to their matched events. It enables quick
 // events look up by watcher.
 func newWatcherBatch(wg *watcherGroup, evs []mvccpb.Event) watcherBatch {
+	if len(wg.watchers) == 0 {
+		return nil
+	}
+
 	wb := make(watcherBatch)
 	for _, ev := range evs {
 		for w := range wg.watcherSetByKey(string(ev.Kv.Key)) {