From ab490723629cd50ab49cc699023c5af31ab427e7 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Mon, 22 Jul 2019 12:10:51 +0200
Subject: [PATCH] Client side caching: don't hash the key if not needed.

---
 src/tracking.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/src/tracking.c b/src/tracking.c
index 5938efade..7ee4d0b2c 100644
--- a/src/tracking.c
+++ b/src/tracking.c
@@ -156,12 +156,15 @@ void sendTrackingMessage(client *c, long long hash) {
 
 /* This function is called from signalModifiedKey() or other places in Redis
  * when a key changes value. In the context of keys tracking, our task here is
- * to send a notification to every client that may have keys about such . */
+ * to send a notification to every client that may have keys about such caching
+ * slot. */
 void trackingInvalidateKey(robj *keyobj) {
+    if (TrackingTable == NULL || TrackingTableUsedSlots == 0) return;
+
     sds sdskey = keyobj->ptr;
     uint64_t hash = crc64(0,
         (unsigned char*)sdskey,sdslen(sdskey))&(TRACKING_TABLE_SIZE-1);
-    if (TrackingTable == NULL || TrackingTable[hash] == NULL) return;
+    if (TrackingTable[hash] == NULL) return;
 
     raxIterator ri;
     raxStart(&ri,TrackingTable[hash]);