Remove dead code on sorting reply on Lua scripts. (#10701)

On v6.2.7 a new mechanism was added to Lua scripts that allows
filtering the globals of the Lua interpreter. This mechanism was
added on the following commit: https://github.com/redis/redis/commit/11b602fbf8f9cdf8fc741c24625ab6287ab998a9

One of the globals that was filtered out was `__redis__compare_helper`. This global
was missed and was not added to the allow list or to the deny list. This is
why we get the following warning when Redis starts:
`A key '__redis__compare_helper' was added to Lua globals which is not on the globals allow list nor listed on the deny list.`

After investigating the git blame log, the conclusion is that `__redis__compare_helper`
is no longer needed, the PR deletes this function, and fixes the warning.

Detailed Explanation:

`__redis__compare_helper` was added on this commit: https://github.com/redis/redis/commit/2c861050c1
Its purpose is to sort the replies of `SORT` command when script replication is enable and keep the replies
deterministic and avoid primary and replica synchronization issues. On `SORT` command, there was a need for
special compare function that are able to compare boolean values.

The need to sort the `SORT` command reply was removed on this commit: https://github.com/redis/redis/commit/36741b2c818a95e8ef167818271614ee6b1bc414
The sorting was moved to be part of the `SORT` command and there was not longer a need
to sort it on the Lua interpreter. The commit made `__redis__compare_helper` a dead code but did
not deleted it.

(cherry picked from commit 64c657a8af03c6d58507b9620947491f36e75037)

1 files changed, 1 insertions, 27 deletions

diff --git a/src/scripting.c b/src/scripting.c
index c5393c16e..42d26537b 100644
--- a/src/scripting.c
+++ b/src/scripting.c
@@ -328,21 +328,7 @@ void luaSortArray(lua_State *lua) {
     lua_pushstring(lua,"sort");
     lua_gettable(lua,-2);       /* Stack: array, table, table.sort */
     lua_pushvalue(lua,-3);      /* Stack: array, table, table.sort, array */
-    if (lua_pcall(lua,1,0,0)) {
-        /* Stack: array, table, error */
-
-        /* We are not interested in the error, we assume that the problem is
-         * that there are 'false' elements inside the array, so we try
-         * again with a slower function but able to handle this case, that
-         * is: table.sort(table, __redis__compare_helper) */
-        lua_pop(lua,1);             /* Stack: array, table */
-        lua_pushstring(lua,"sort"); /* Stack: array, table, sort */
-        lua_gettable(lua,-2);       /* Stack: array, table, table.sort */
-        lua_pushvalue(lua,-3);      /* Stack: array, table, table.sort, array */
-        lua_getglobal(lua,"__redis__compare_helper");
-        /* Stack: array, table, table.sort, array, __redis__compare_helper */
-        lua_call(lua,2,0);
-    }
+    lua_call(lua,1,0);          /* Stack: array (sorted), table */
     /* Stack: array (sorted), table */
     lua_pop(lua,1);             /* Stack: array (sorted) */
 }
@@ -1256,18 +1242,6 @@ void scriptingInit(int setup) {
 
     lua_setglobal(lua,"math");
 
-    /* Add a helper function that we use to sort the multi bulk output of non
-     * deterministic commands, when containing 'false' elements. */
-    {
-        char *compare_func =    "function __redis__compare_helper(a,b)\n"
-                                "  if a == false then a = '' end\n"
-                                "  if b == false then b = '' end\n"
-                                "  return a<b\n"
-                                "end\n";
-        luaL_loadbuffer(lua,compare_func,strlen(compare_func),"@cmp_func_def");
-        lua_pcall(lua,0,0,0);
-    }
-
     /* Add a helper function we use for pcall error reporting.
      * Note that when the error is in the C function we want to report the
      * information about the caller, that's what makes sense from the point