From 521ddcce1483d1b8760a108fd5d7df0ae663799a Mon Sep 17 00:00:00 2001
From: antirez <antirez@gmail.com>
Date: Thu, 19 May 2011 17:58:29 +0200
Subject: [PATCH] Fix for ZUNIONSTORE bug when there is an empty set among
 input sets. Regression test added.

---
 src/t_zset.c             | 2 +-
 tests/unit/type/zset.tcl | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/src/t_zset.c b/src/t_zset.c
index 1c55cb97..19aac3d5 100644
--- a/src/t_zset.c
+++ b/src/t_zset.c
@@ -1550,7 +1550,7 @@ void zunionInterGenericCommand(redisClient *c, robj *dstkey, int op) {
         }
     } else if (op == REDIS_OP_UNION) {
         for (i = 0; i < setnum; i++) {
-            if (zuiLength(&src[0]) == 0)
+            if (zuiLength(&src[i]) == 0)
                 continue;
 
             while (zuiNext(&src[i],&zval)) {
diff --git a/tests/unit/type/zset.tcl b/tests/unit/type/zset.tcl
index 37668cfe..761cac49 100644
--- a/tests/unit/type/zset.tcl
+++ b/tests/unit/type/zset.tcl
@@ -353,6 +353,14 @@ start_server {tags {"zset"}} {
             assert_equal 0 [r exists dst_key]
         }
 
+        test "ZUNIONSTORE with empty set - $encoding" {
+            r del zseta zsetb
+            r zadd zseta 1 a
+            r zadd zseta 2 b
+            r zunionstore zsetc 2 zseta zsetb
+            r zrange zsetc 0 -1 withscores
+        } {a 1 b 2}
+
         test "ZUNIONSTORE basics - $encoding" {
             r del zseta zsetb zsetc
             r zadd zseta 1 a
-- 
2.45.2