optimize zset conversion on large ZRANGESTORE (redis#10789)

when we know the size of the zset we're gonna store in advance,
we can check if it's greater than the listpack encoding threshold,
in which case we can create a skiplist from the get go, and avoid
converting the listpack to skiplist later after it was already populated.

Author: oranagra

src/t_zset.c

@@ -2952,8 +2952,10 @@ static void zrangeResultFinalizeClient(zrange_result_handler *handler,
 /* Result handler methods for storing the ZRANGESTORE to a zset. */
 static void zrangeResultBeginStore(zrange_result_handler *handler, long length)
 {
-    UNUSED(length);
-    handler->dstobj = createZsetListpackObject();
+    if (length > (long)server.zset_max_listpack_entries)
+        handler->dstobj = createZsetObject();
+    else
+        handler->dstobj = createZsetListpackObject();
 }
 
 static void zrangeResultEmitCBufferForStore(zrange_result_handler *handler,

tests/unit/type/zset.tcl

@@ -2208,7 +2208,7 @@ start_server {tags {"zset"}} {
         assert_match "*syntax*" $err
     }
 
-    test {ZRANGESTORE with zset-max-listpack-entries 0 dst key should use skiplist encoding} {
+    test {ZRANGESTORE with zset-max-listpack-entries 0 #10767 case} {
         set original_max [lindex [r config get zset-max-listpack-entries] 1]
         r config set zset-max-listpack-entries 0
         r del z1{t} z2{t}
@@ -2217,6 +2217,18 @@ start_server {tags {"zset"}} {
         r config set zset-max-listpack-entries $original_max
     }
 
+    test {ZRANGESTORE with zset-max-listpack-entries 1 dst key should use skiplist encoding} {
+        set original_max [lindex [r config get zset-max-listpack-entries] 1]
+        r config set zset-max-listpack-entries 1
+        r del z1{t} z2{t} z3{t}
+        r zadd z1{t} 1 a 2 b
+        assert_equal 1 [r zrangestore z2{t} z1{t} 0 0]
+        assert_encoding listpack z2{t}
+        assert_equal 2 [r zrangestore z3{t} z1{t} 0 1]
+        assert_encoding skiplist z3{t}
+        r config set zset-max-listpack-entries $original_max
+    }
+
     test {ZRANGE invalid syntax} {
         catch {r zrange z1{t} 0 -1 limit 1 2} err
         assert_match "*syntax*" $err