Function FunctionCall

src/storage/scripting.cc:400–470

FunctionCall will firstly find the function in the lua runtime, if it is not found, it will try to load the library where the function is located from storage

// FunctionCall will firstly find the function in the lua runtime,
// if it is not found, it will try to load the library where the function is located from storage
Status FunctionCall(redis::Connection *conn, engine::Context *ctx, const std::string &name,
                    const std::vector<std::string> &keys, const std::vector<std::string> &argv, std::string *output,
                    bool read_only) {
  auto srv = conn->GetServer();
  auto lua = conn->Owner()->Lua();

  lua_getglobal(lua, "__redis__err__handler");

  lua_getglobal(lua, (REDIS_LUA_REGISTER_FUNC_PREFIX + name).c_str());
  if (lua_isnil(lua, -1)) {
    lua_pop(lua, 1);

    std::string libname;
    auto s = srv->FunctionGetLib(name, &libname);
    if (!s) return s.Prefixed("No such function name found in storage");

    std::string libcode;
    s = srv->FunctionGetCode(libname, &libcode);
    if (!s) return s;
    s = FunctionLoad(conn, ctx, libcode, false, false, &libname);
    if (!s) return s;

    lua_getglobal(lua, (REDIS_LUA_REGISTER_FUNC_PREFIX + name).c_str());
  }

  ScriptRunCtx script_run_ctx;
  script_run_ctx.conn = conn;
  script_run_ctx.ctx = ctx;
  script_run_ctx.flags = read_only ? ScriptFlagType::kScriptNoWrites : 0;
  lua_getglobal(lua, (REDIS_LUA_REGISTER_FUNC_FLAGS_PREFIX + name).c_str());
  if (!lua_isnil(lua, -1)) {
    // It should be ensured that the conversion is successful
    auto function_flags = lua_tointeger(lua, -1);
    script_run_ctx.flags |= function_flags;
  }
  lua_pop(lua, 1);

  SaveOnRegistry(lua, REGISTRY_SCRIPT_RUN_CTX_NAME, &script_run_ctx);

  // save keys on registry the to perform key touching check
  SaveOnRegistry(lua, REGISTRY_KEYS_NAME, &keys);

  PushArray(lua, keys);
  PushArray(lua, argv);
  if (lua_pcall(lua, 2, 1, -4)) {
    std::string err_msg = lua_tostring(lua, -1);
    lua_pop(lua, 2);
    return {Status::NotOK, fmt::format("Error while running function `{}`: {}", name, err_msg)};
  } else {
    *output = ReplyToRedisReply(conn, lua);
    lua_pop(lua, 2);
  }

  RemoveFromRegistry(lua, REGISTRY_KEYS_NAME);
  RemoveFromRegistry(lua, REGISTRY_SCRIPT_RUN_CTX_NAME);

  /* Call the Lua garbage collector from time to time to avoid a
   * full cycle performed by Lua, which adds too latency.