From 0b561883b48db76a78497b1bebfd9367c80e2d96 Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Fri, 22 Dec 2017 11:26:31 +0100
Subject: [PATCH] Hyperloglog: refresh hdr variable correctly.

This is a fix for the #3819 improvements. The o->ptr may change because
of hllSparseSet() calls, so 'hdr' must be correctly re-fetched.
---
 src/hyperloglog.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/hyperloglog.c b/src/hyperloglog.c
index 65fbfd06..ef33979a 100644
--- a/src/hyperloglog.c
+++ b/src/hyperloglog.c
@@ -1347,14 +1347,16 @@ void pfmergeCommand(client *c) {
 
     /* Write the resulting HLL to the destination HLL registers and
      * invalidate the cached value. */
-    hdr = o->ptr;
     for (j = 0; j < HLL_REGISTERS; j++) {
         if (max[j] == 0) continue;
+        hdr = o->ptr;
         switch(hdr->encoding) {
         case HLL_DENSE: hllDenseSet(hdr->registers,j,max[j]); break;
         case HLL_SPARSE: hllSparseSet(o,j,max[j]); break;
         }
     }
+    hdr = o->ptr; /* o->ptr may be different now, as a side effect of
+                     last hllSparseSet() call. */
     HLL_INVALIDATE_CACHE(hdr);
 
     signalModifiedKey(c->db,c->argv[1]);