[PATCH v1 2/3] schema: extend _func space to persist lua functions

[Kirill Shcherbatov <kshcherbatov@tarantool.org>]

This patch extends _func system space with a new string field
lua_code to persist Lua functions.

Refactored func hash machinery to pass a new function object and
to return previous one. This allows to implement fault-tolerant
func_new call that constructs a lua function object.

Each persistent function may use limited amount of Lua functions
and modules:
-assert -error -pairs -ipairs -next -pcall -xpcall -type
-print -select -string -tonumber -tostring -unpack -math -utf8
Global variables are forbidden in persistent Lua functions.

This patch makes persistent Lua functions are available via
net.box.connect() :call method.
Example:
lua_code = [[function(a, b) return a + b end]]
box.schema.func.create('sum', {lua_code = lua_code})
conn:call("sum", {1, 3})

Part of #4182
Needed for #1260
---
 src/box/alter.cc                  |  85 +++++++++++-----
 src/box/bootstrap.snap            | Bin 4374 -> 4393 bytes
 src/box/call.c                    |   2 +-
 src/box/func.c                    | 109 ++++++++++++++++++--
 src/box/func.h                    |  15 ++-
 src/box/func_def.h                |  10 +-
 src/box/lua/call.c                |  40 +++++++-
 src/box/lua/call.h                |   4 +-
 src/box/lua/schema.lua            |   7 +-
 src/box/lua/upgrade.lua           |  15 +++
 src/box/schema.cc                 |  46 ++++-----
 src/box/schema.h                  |  15 +--
 src/box/schema_def.h              |   1 +
 test/box-py/bootstrap.result      |   6 +-
 test/box/access_misc.result       |   4 +-
 test/box/persistent_func.result   | 163 ++++++++++++++++++++++++++++++
 test/box/persistent_func.test.lua |  78 ++++++++++++++
 17 files changed, 517 insertions(+), 83 deletions(-)
 create mode 100644 test/box/persistent_func.result
 create mode 100644 test/box/persistent_func.test.lua

diff --git a/src/box/alter.cc b/src/box/alter.cc
index 9279426d2..0d23dbf0e 100644
--- a/src/box/alter.cc
+++ b/src/box/alter.cc
@@ -2402,21 +2402,41 @@ func_def_get_ids_from_tuple(struct tuple *tuple, uint32_t *fid, uint32_t *uid)
 static struct func_def *
 func_def_new_from_tuple(struct tuple *tuple)
 {
-	uint32_t len;
-	const char *name = tuple_field_str_xc(tuple, BOX_FUNC_FIELD_NAME,
-					      &len);
-	if (len > BOX_NAME_MAX)
+	uint32_t name_len, lua_code_len;
+	const char *name, *lua_code;
+	name = tuple_field_str_xc(tuple, BOX_FUNC_FIELD_NAME, &name_len);
+	if (name_len > BOX_NAME_MAX) {
 		tnt_raise(ClientError, ER_CREATE_FUNCTION,
 			  tt_cstr(name, BOX_INVALID_NAME_MAX),
 			  "function name is too long");
-	identifier_check_xc(name, len);
-	struct func_def *def = (struct func_def *) malloc(func_def_sizeof(len));
+	}
+	identifier_check_xc(name, name_len);
+	if (tuple_field_count(tuple) > BOX_FUNC_FIELD_LUA_CODE) {
+		lua_code = tuple_field_str_xc(tuple, BOX_FUNC_FIELD_LUA_CODE,
+					      &lua_code_len);
+	} else {
+		lua_code = NULL;
+		lua_code_len = 0;
+	}
+
+	uint32_t def_sz = func_def_sizeof(name_len, lua_code_len);
+	struct func_def *def = (struct func_def *) malloc(def_sz);
 	if (def == NULL)
-		tnt_raise(OutOfMemory, func_def_sizeof(len), "malloc", "def");
+		tnt_raise(OutOfMemory, def_sz, "malloc", "def");
 	auto def_guard = make_scoped_guard([=] { free(def); });
 	func_def_get_ids_from_tuple(tuple, &def->fid, &def->uid);
-	memcpy(def->name, name, len);
-	def->name[len] = 0;
+
+	def->name = (char *)def + sizeof(struct func_def);
+	memcpy(def->name, name, name_len);
+	def->name[name_len] = 0;
+	if (lua_code_len > 0) {
+		def->lua_code = def->name + name_len + 1;
+		memcpy(def->lua_code, lua_code, lua_code_len);
+		def->lua_code[lua_code_len] = 0;
+	} else {
+		def->lua_code = NULL;
+	}
+
 	if (tuple_field_count(tuple) > BOX_FUNC_FIELD_SETUID)
 		def->setuid = tuple_field_u32_xc(tuple, BOX_FUNC_FIELD_SETUID);
 	else
@@ -2433,30 +2453,32 @@ func_def_new_from_tuple(struct tuple *tuple)
 		/* Lua is the default. */
 		def->language = FUNC_LANGUAGE_LUA;
 	}
+	if (def->language != FUNC_LANGUAGE_LUA && lua_code_len > 0) {
+		tnt_raise(ClientError, ER_CREATE_FUNCTION, name,
+			  "function lua_code may be specified only for "
+			  "Lua language");
+	}
 	def_guard.is_active = false;
 	return def;
 }
 
 /** Remove a function from function cache */
 static void
-func_cache_remove_func(struct trigger * /* trigger */, void *event)
+func_cache_remove_func(struct trigger *trigger, void * /* event */)
 {
-	struct txn_stmt *stmt = txn_last_stmt((struct txn *) event);
-	uint32_t fid = tuple_field_u32_xc(stmt->old_tuple ?
-				       stmt->old_tuple : stmt->new_tuple,
-				       BOX_FUNC_FIELD_ID);
-	func_cache_delete(fid);
+	struct func *old_func = (struct func *) trigger->data;
+	func_cache_delete(old_func->def->fid);
+	func_delete(old_func);
 }
 
 /** Replace a function in the function cache */
 static void
-func_cache_replace_func(struct trigger * /* trigger */, void *event)
+func_cache_replace_func(struct trigger *trigger, void * /* event */)
 {
-	struct txn_stmt *stmt = txn_last_stmt((struct txn*) event);
-	struct func_def *def = func_def_new_from_tuple(stmt->new_tuple);
-	auto def_guard = make_scoped_guard([=] { free(def); });
-	func_cache_replace(def);
-	def_guard.is_active = false;
+	struct func *new_func = (struct func *) trigger->data;
+	struct func *old_func;
+	func_cache_replace(new_func, &old_func);
+	func_delete(old_func);
 }
 
 /**
@@ -2477,13 +2499,20 @@ on_replace_dd_func(struct trigger * /* trigger */, void *event)
 	struct func *old_func = func_by_id(fid);
 	if (new_tuple != NULL && old_func == NULL) { /* INSERT */
 		struct func_def *def = func_def_new_from_tuple(new_tuple);
+		auto def_guard = make_scoped_guard([=] { free(def); });
 		access_check_ddl(def->name, def->fid, def->uid, SC_FUNCTION,
 				 PRIV_C);
-		auto def_guard = make_scoped_guard([=] { free(def); });
-		func_cache_replace(def);
+		struct func *func = func_new(def);
+		if (func == NULL)
+			diag_raise();
+		auto func_guard = make_scoped_guard([=] { func_delete(func); });
 		def_guard.is_active = false;
+		struct func *old_func = NULL;
+		func_cache_replace(func, &old_func);
+		assert(old_func == NULL);
+		func_guard.is_active = false;
 		struct trigger *on_rollback =
-			txn_alter_trigger_new(func_cache_remove_func, NULL);
+			txn_alter_trigger_new(func_cache_remove_func, func);
 		txn_on_rollback(txn, on_rollback);
 	} else if (new_tuple == NULL) {         /* DELETE */
 		uint32_t uid;
@@ -2501,15 +2530,19 @@ on_replace_dd_func(struct trigger * /* trigger */, void *event)
 				  "function has grants");
 		}
 		struct trigger *on_commit =
-			txn_alter_trigger_new(func_cache_remove_func, NULL);
+			txn_alter_trigger_new(func_cache_remove_func, old_func);
 		txn_on_commit(txn, on_commit);
 	} else {                                /* UPDATE, REPLACE */
 		struct func_def *def = func_def_new_from_tuple(new_tuple);
 		auto def_guard = make_scoped_guard([=] { free(def); });
 		access_check_ddl(def->name, def->fid, def->uid, SC_FUNCTION,
 				 PRIV_A);
+		struct func *func = func_new(def);
+		if (func == NULL)
+			diag_raise();
+		def_guard.is_active = false;
 		struct trigger *on_commit =
-			txn_alter_trigger_new(func_cache_replace_func, NULL);
+			txn_alter_trigger_new(func_cache_replace_func, func);
 		txn_on_commit(txn, on_commit);
 	}
 }

diff --git a/src/box/call.c b/src/box/call.c
index 56da53fb3..773b914b1 100644
--- a/src/box/call.c
+++ b/src/box/call.c
@@ -202,7 +202,7 @@ box_process_call(struct call_request *request, struct port *port)
 	if (func && func->def->language == FUNC_LANGUAGE_C) {
 		rc = box_c_call(func, request, port);
 	} else {
-		rc = box_lua_call(request, port);
+		rc = box_lua_call(func, request, port);
 	}
 	/* Restore the original user */
 	if (orig_credentials)
diff --git a/src/box/func.c b/src/box/func.c
index a817851fd..b68c089ad 100644
--- a/src/box/func.c
+++ b/src/box/func.c
@@ -29,11 +29,13 @@
  * SUCH DAMAGE.
  */
 #include "func.h"
+#include "box/lua/util.h"
 #include "trivia/config.h"
 #include "assoc.h"
 #include "lua/utils.h"
 #include "error.h"
 #include "diag.h"
+#include "fiber.h"
 #include <dlfcn.h>
 
 /**
@@ -355,6 +357,88 @@ restore:
 	return -1;
 }
 
+/**
+ * Assemble a Lua function object on Lua stack and return
+ * the reference.
+ * Returns func object reference on success, -1 otherwise.
+ */
+static int
+func_lua_code_load(struct func_def *def)
+{
+	int rc = -1;
+	struct region *region = &fiber()->gc;
+	size_t region_svp = region_used(region);
+	struct lua_State *L = lua_newthread(tarantool_L);
+	int coro_ref = luaL_ref(tarantool_L, LUA_REGISTRYINDEX);
+
+	const char *load_pref = "return ";
+	uint32_t load_str_sz =
+		strlen(load_pref) + strlen(def->lua_code) + 1;
+	char *load_str = region_alloc(region, load_str_sz);
+	if (load_str == NULL) {
+		diag_set(OutOfMemory, load_str_sz, "region",
+				"load_str");
+		goto end;
+	}
+	sprintf(load_str, "%s%s", load_pref, def->lua_code);
+	if (luaL_loadstring(L, load_str) != 0 ||
+	    lua_pcall(L, 0, 1, 0) != 0 || !lua_isfunction(L, -1)) {
+		diag_set(ClientError, ER_LOAD_FUNCTION, def->name,
+			def->lua_code);
+		goto end;
+	}
+	/*
+	 * Allow assembled function to use only a limited number
+	 * of functions and modules. All modules are exported
+	 * via deepcopy to prevent the user from overriding
+	 * the system context.
+	 *
+	 * The debug.getinfo() inspection for upvalues is
+	 * redundant, because no one can create function that
+	 * doesn't return function and that has such env_exports
+	 * restrictions.
+	 */
+	int count;
+	const char *deepcopy = "table.deepcopy";
+	if (luaT_func_find(L, deepcopy, deepcopy + strlen(deepcopy),
+			   &count) != 0)
+		goto end;
+	int deepcopy_ref = luaL_ref(L, LUA_REGISTRYINDEX);
+	struct {
+		const char *name;
+		bool deep_copy;
+	} env_exports[] = {
+		{"assert", false}, {"error", false}, {"ipairs", false},
+		{"math", true}, {"next", false}, {"pairs", false},
+		{"pcall", false}, {"print", false}, {"select", false},
+		{"string", true}, {"table", true}, {"tonumber", false},
+		{"tostring", false}, {"type", false}, {"unpack", false},
+		{"xpcall", false}, {"utf8", false}
+	};
+	lua_createtable(L, nelem(env_exports), 0);
+	for (unsigned i = 0; i < nelem(env_exports); i++) {
+		uint32_t name_len = strlen(env_exports[i].name);
+		if (env_exports[i].deep_copy)
+			lua_rawgeti(L, LUA_REGISTRYINDEX, deepcopy_ref);
+		if (luaT_func_find(L, env_exports[i].name,
+				   env_exports[i].name + name_len,
+				   &count) != 0) {
+			luaL_unref(L, LUA_REGISTRYINDEX, deepcopy_ref);
+			goto end;
+		}
+		if (env_exports[i].deep_copy)
+			lua_call(L, 1, LUA_MULTRET);
+		lua_setfield(L, -2, env_exports[i].name);
+	}
+	lua_setfenv(L, -2);
+	luaL_unref(L, LUA_REGISTRYINDEX, deepcopy_ref);
+	rc = luaL_ref(L, LUA_REGISTRYINDEX);
+end:
+	region_truncate(region, region_svp);
+	luaL_unref(L, LUA_REGISTRYINDEX, coro_ref);
+	return rc;
+}
+
 struct func *
 func_new(struct func_def *def)
 {
@@ -380,6 +464,15 @@ func_new(struct func_def *def)
 	func->owner_credentials.auth_token = BOX_USER_MAX; /* invalid value */
 	func->func = NULL;
 	func->module = NULL;
+	if (func->def->lua_code != NULL) {
+		func->lua_func_ref = func_lua_code_load(def);
+		if (func->lua_func_ref == -1) {
+			free(func);
+			return NULL;
+		}
+	} else {
+		func->lua_func_ref = -1;
+	}
 	return func;
 }
 
@@ -395,8 +488,11 @@ func_unload(struct func *func)
 		}
 		module_gc(func->module);
 	}
+	if (func->lua_func_ref != -1)
+		luaL_unref(tarantool_L, LUA_REGISTRYINDEX, func->lua_func_ref);
 	func->module = NULL;
 	func->func = NULL;
+	func->lua_func_ref = -1;
 }
 
 /**
@@ -452,17 +548,18 @@ func_call(struct func *func, box_function_ctx_t *ctx, const char *args,
 }
 
 void
-func_update(struct func *func, struct func_def *def)
+func_delete(struct func *func)
 {
 	func_unload(func);
 	free(func->def);
-	func->def = def;
+	free(func);
 }
 
 void
-func_delete(struct func *func)
+func_capture_module(struct func *new_func, struct func *old_func)
 {
-	func_unload(func);
-	free(func->def);
-	free(func);
+	new_func->module = old_func->module;
+	new_func->func = old_func->func;
+	old_func->module = NULL;
+	old_func->func = NULL;
 }
diff --git a/src/box/func.h b/src/box/func.h
index 8dcd61d7b..b00ed5690 100644
--- a/src/box/func.h
+++ b/src/box/func.h
@@ -65,6 +65,11 @@ struct func {
 	 * Anchor for module membership.
 	 */
 	struct rlist item;
+	/**
+	 * The reference index of Lua function object.
+	 * Is equal to -1 when undefined.
+	 */
+	int lua_func_ref;
 	/**
 	 * For C functions, the body of the function.
 	 */
@@ -100,9 +105,6 @@ module_free(void);
 struct func *
 func_new(struct func_def *def);
 
-void
-func_update(struct func *func, struct func_def *def);
-
 void
 func_delete(struct func *func);
 
@@ -113,6 +115,13 @@ int
 func_call(struct func *func, box_function_ctx_t *ctx, const char *args,
 	  const char *args_end);
 
+/**
+ * Take over the modules that belonged to the old function.
+ * Reset module and function pointers in onl function.
+*/
+void
+func_capture_module(struct func *new_func, struct func *old_func);
+
 /**
  * Reload dynamically loadable module.
  *
diff --git a/src/box/func_def.h b/src/box/func_def.h
index 5b52ab498..19a4df959 100644
--- a/src/box/func_def.h
+++ b/src/box/func_def.h
@@ -54,6 +54,10 @@ struct func_def {
 	uint32_t fid;
 	/** Owner of the function. */
 	uint32_t uid;
+	/** Function name. */
+	char *name;
+	/** The Lua function code.  */
+	char *lua_code;
 	/**
 	 * True if the function requires change of user id before
 	 * invocation.
@@ -63,8 +67,6 @@ struct func_def {
 	 * The language of the stored function.
 	 */
 	enum func_language language;
-	/** Function name. */
-	char name[0];
 };
 
 /**
@@ -73,10 +75,10 @@ struct func_def {
  * for a function of length @a a name_len.
  */
 static inline size_t
-func_def_sizeof(uint32_t name_len)
+func_def_sizeof(uint32_t name_len, uint32_t lua_code_len)
 {
 	/* +1 for '\0' name terminating. */
-	return sizeof(struct func_def) + name_len + 1;
+	return sizeof(struct func_def) + name_len + 1 + lua_code_len + 1;
 }
 
 /**
diff --git a/src/box/lua/call.c b/src/box/lua/call.c
index 1a0fb4df0..496c00e83 100644
--- a/src/box/lua/call.c
+++ b/src/box/lua/call.c
@@ -32,6 +32,8 @@
 #include "box/call.h"
 #include "box/error.h"
 #include "fiber.h"
+#include "box/func.h"
+#include "box/schema.h"
 
 #include "lua/utils.h"
 #include "lua/msgpack.h"
@@ -250,6 +252,37 @@ execute_lua_call(lua_State *L)
 	return lua_gettop(L);
 }
 
+/**
+ * Execute the persistent Lua function.
+ * Assemble Lua object when required.
+ */
+static int
+execute_lua_ref_call(lua_State *L)
+{
+	struct call_request *request = (struct call_request *)
+		lua_topointer(L, 1);
+	lua_settop(L, 0);
+
+	const char *name = request->name;
+	uint32_t name_len = mp_decode_strl(&name);
+
+	struct func *func = func_by_name(name, name_len);
+	assert(func != NULL);
+	/* Construct Lua function if required. */
+	assert(func->lua_func_ref != -1);
+	lua_rawgeti(L, LUA_REGISTRYINDEX, func->lua_func_ref);
+
+	/* Push the rest of args (a tuple). */
+	const char *args = request->args;
+	uint32_t arg_count = mp_decode_array(&args);
+	luaL_checkstack(L, arg_count, "lua_func: out of stack");
+	for (uint32_t i = 0; i < arg_count; i++)
+		luamp_decode(L, luaL_msgpack_default, &args);
+
+	lua_call(L, arg_count, LUA_MULTRET);
+	return lua_gettop(L);
+}
+
 static int
 execute_lua_eval(lua_State *L)
 {
@@ -393,9 +426,12 @@ box_process_lua(struct call_request *request, struct port *base,
 }
 
 int
-box_lua_call(struct call_request *request, struct port *port)
+box_lua_call(struct func *func, struct call_request *request, struct port *port)
 {
-	return box_process_lua(request, port, execute_lua_call);
+	if (func != NULL && func->def->lua_code != NULL)
+		return box_process_lua(request, port, execute_lua_ref_call);
+	else
+		return box_process_lua(request, port, execute_lua_call);
 }
 
 int
diff --git a/src/box/lua/call.h b/src/box/lua/call.h
index 0542123da..d8ef65900 100644
--- a/src/box/lua/call.h
+++ b/src/box/lua/call.h
@@ -42,13 +42,15 @@ box_lua_call_init(struct lua_State *L);
 
 struct port;
 struct call_request;
+struct func;
 
 /**
  * Invoke a Lua stored procedure from the binary protocol
  * (implementation of 'CALL' command code).
  */
 int
-box_lua_call(struct call_request *request, struct port *port);
+box_lua_call(struct func *func, struct call_request *request,
+	     struct port *port);
 
 int
 box_lua_eval(struct call_request *request, struct port *port);
diff --git a/src/box/lua/schema.lua b/src/box/lua/schema.lua
index f31cf7f2c..ca7da6501 100644
--- a/src/box/lua/schema.lua
+++ b/src/box/lua/schema.lua
@@ -1981,7 +1981,8 @@ box.schema.func.create = function(name, opts)
     opts = opts or {}
     check_param_table(opts, { setuid = 'boolean',
                               if_not_exists = 'boolean',
-                              language = 'string'})
+                              language = 'string',
+                              lua_code = 'string' })
     local _func = box.space[box.schema.FUNC_ID]
     local _vfunc = box.space[box.schema.VFUNC_ID]
     local func = _vfunc.index.name:get{name}
@@ -1991,10 +1992,10 @@ box.schema.func.create = function(name, opts)
         end
         return
     end
-    opts = update_param_table(opts, { setuid = false, language = 'lua'})
+    opts = update_param_table(opts, { setuid = false, language = 'lua', lua_code = ''})
     opts.language = string.upper(opts.language)
     opts.setuid = opts.setuid and 1 or 0
-    _func:auto_increment{session.euid(), name, opts.setuid, opts.language}
+    _func:auto_increment{session.euid(), name, opts.setuid, opts.language, opts.lua_code}
 end
 
 box.schema.func.drop = function(name, opts)
diff --git a/src/box/lua/upgrade.lua b/src/box/lua/upgrade.lua
index 89d6e3d52..c5296fc69 100644
--- a/src/box/lua/upgrade.lua
+++ b/src/box/lua/upgrade.lua
@@ -737,6 +737,20 @@ local function upgrade_to_2_1_3()
     end
 end
 
+local function upgrade_to_2_2_0()
+    local _func = box.space[box.schema.FUNC_ID]
+    local format = {}
+    format[1] = {name='id', type='unsigned'}
+    format[2] = {name='owner', type='unsigned'}
+    format[3] = {name='name', type='string'}
+    format[4] = {name='setuid', type='unsigned'}
+    format[5] = {name='lua_code', type='string'}
+    for _, v in box.space._func:pairs() do
+        box.space._func:replace(v:update{{'=', #v + 1, ''}})
+    end
+    _func:format(format)
+end
+
 local function get_version()
     local version = box.space._schema:get{'version'}
     if version == nil then
@@ -768,6 +782,7 @@ local function upgrade(options)
         {version = mkversion(2, 1, 1), func = upgrade_to_2_1_1, auto = true},
         {version = mkversion(2, 1, 2), func = upgrade_to_2_1_2, auto = true},
         {version = mkversion(2, 1, 3), func = upgrade_to_2_1_3, auto = true},
+        {version = mkversion(2, 2, 0), func = upgrade_to_2_2_0, auto = true},
     }
 
     for _, handler in ipairs(handlers) do
diff --git a/src/box/schema.cc b/src/box/schema.cc
index 9a55c2f14..aae92874c 100644
--- a/src/box/schema.cc
+++ b/src/box/schema.cc
@@ -533,40 +533,35 @@ schema_free(void)
 }
 
 void
-func_cache_replace(struct func_def *def)
+func_cache_replace(struct func *new_func, struct func **old_func)
 {
-	struct func *old = func_by_id(def->fid);
-	if (old) {
-		func_update(old, def);
-		return;
-	}
 	if (mh_size(funcs) >= BOX_FUNCTION_MAX)
 		tnt_raise(ClientError, ER_FUNCTION_MAX, BOX_FUNCTION_MAX);
-	struct func *func = func_new(def);
-	if (func == NULL) {
-error:
-		panic_syserror("Out of memory for the data "
-			       "dictionary cache (stored function).");
-	}
-	const struct mh_i32ptr_node_t node = { def->fid, func };
-	mh_int_t k1 = mh_i32ptr_put(funcs, &node, NULL, NULL);
-	if (k1 == mh_end(funcs)) {
-		func->def = NULL;
-		func_delete(func);
-		goto error;
-	}
-	size_t def_name_len = strlen(func->def->name);
-	uint32_t name_hash = mh_strn_hash(func->def->name, def_name_len);
+
+	mh_int_t k1, k2;
+	struct mh_i32ptr_node_t *old_node = NULL;
+	const struct mh_i32ptr_node_t node = { new_func->def->fid, new_func };
+	size_t def_name_len = strlen(new_func->def->name);
+	uint32_t name_hash = mh_strn_hash(new_func->def->name, def_name_len);
 	const struct mh_strnptr_node_t strnode = {
-		func->def->name, def_name_len, name_hash, func };
+		new_func->def->name, def_name_len, name_hash, new_func };
 
-	mh_int_t k2 = mh_strnptr_put(funcs_by_name, &strnode, NULL, NULL);
+	k1 = mh_i32ptr_put(funcs, &node, &old_node, NULL);
+	if (k1 == mh_end(funcs))
+		goto error;
+	if (old_node != NULL)
+		*old_func = (struct func *)old_node->val;
+	k2 = mh_strnptr_put(funcs_by_name, &strnode, NULL, NULL);
 	if (k2 == mh_end(funcs_by_name)) {
 		mh_i32ptr_del(funcs, k1, NULL);
-		func->def = NULL;
-		func_delete(func);
 		goto error;
 	}
+	if (*old_func != NULL)
+		func_capture_module(new_func, *old_func);
+	return;
+error:
+	panic_syserror("Out of memory for the data dictionary cache "
+		       "(stored function).");
 }
 
 void
@@ -582,7 +577,6 @@ func_cache_delete(uint32_t fid)
 				strlen(func->def->name));
 	if (k != mh_end(funcs))
 		mh_strnptr_del(funcs_by_name, k, NULL);
-	func_delete(func);
 }
 
 struct func *
diff --git a/src/box/schema.h b/src/box/schema.h
index 6f9a96117..bc15c8a2c 100644
--- a/src/box/schema.h
+++ b/src/box/schema.h
@@ -163,14 +163,17 @@ schema_free();
 struct space *schema_space(uint32_t id);
 
 /**
- * Insert a new function or update the old one.
- *
- * @param def Function definition. In a case of success the ownership
- *        of @a def is transfered to the data dictionary, thus the caller
- *        must not delete it.
+ * Replace an existent (if any) function or insert a new one
+ * in function cache.
+ * @param func_new Function object to insert. In case of success,
+ *                 when old function object is exists, all loaded
+ *                 modules data are inherent with
+ *                 func_capture_module.
+ * @param func_old[out] The replaced function object if any.
+ * @retval Returns 0 on success, -1 otherwise.
  */
 void
-func_cache_replace(struct func_def *def);
+func_cache_replace(struct func *new_func, struct func **old_func);
 
 void
 func_cache_delete(uint32_t fid);
diff --git a/src/box/schema_def.h b/src/box/schema_def.h
index eeeeb950b..31d2a594a 100644
--- a/src/box/schema_def.h
+++ b/src/box/schema_def.h
@@ -163,6 +163,7 @@ enum {
 	BOX_FUNC_FIELD_NAME = 2,
 	BOX_FUNC_FIELD_SETUID = 3,
 	BOX_FUNC_FIELD_LANGUAGE = 4,
+	BOX_FUNC_FIELD_LUA_CODE = 5,
 };
 
 /** _collation fields. */
diff --git a/test/box-py/bootstrap.result b/test/box-py/bootstrap.result
index 379f6c51f..ea8ae0984 100644
--- a/test/box-py/bootstrap.result
+++ b/test/box-py/bootstrap.result
@@ -4,7 +4,7 @@ box.internal.bootstrap()
 box.space._schema:select{}
 ---
 - - ['max_id', 511]
-  - ['version', 2, 1, 3]
+  - ['version', 2, 2, 0]
 ...
 box.space._cluster:select{}
 ---
@@ -49,7 +49,7 @@ box.space._space:select{}
         'type': 'string'}, {'name': 'opts', 'type': 'map'}, {'name': 'parts', 'type': 'array'}]]
   - [296, 1, '_func', 'memtx', 0, {}, [{'name': 'id', 'type': 'unsigned'}, {'name': 'owner',
         'type': 'unsigned'}, {'name': 'name', 'type': 'string'}, {'name': 'setuid',
-        'type': 'unsigned'}]]
+        'type': 'unsigned'}, {'name': 'lua_code', 'type': 'string'}]]
   - [297, 1, '_vfunc', 'sysview', 0, {}, [{'name': 'id', 'type': 'unsigned'}, {'name': 'owner',
         'type': 'unsigned'}, {'name': 'name', 'type': 'string'}, {'name': 'setuid',
         'type': 'unsigned'}]]
@@ -141,7 +141,7 @@ box.space._user:select{}
 ...
 box.space._func:select{}
 ---
-- - [1, 1, 'box.schema.user.info', 1, 'LUA']
+- - [1, 1, 'box.schema.user.info', 1, 'LUA', '']
 ...
 box.space._priv:select{}
 ---
diff --git a/test/box/access_misc.result b/test/box/access_misc.result
index 36ebfae09..e1dd9b1cb 100644
--- a/test/box/access_misc.result
+++ b/test/box/access_misc.result
@@ -789,7 +789,7 @@ box.space._space:select()
         'type': 'string'}, {'name': 'opts', 'type': 'map'}, {'name': 'parts', 'type': 'array'}]]
   - [296, 1, '_func', 'memtx', 0, {}, [{'name': 'id', 'type': 'unsigned'}, {'name': 'owner',
         'type': 'unsigned'}, {'name': 'name', 'type': 'string'}, {'name': 'setuid',
-        'type': 'unsigned'}]]
+        'type': 'unsigned'}, {'name': 'lua_code', 'type': 'string'}]]
   - [297, 1, '_vfunc', 'sysview', 0, {}, [{'name': 'id', 'type': 'unsigned'}, {'name': 'owner',
         'type': 'unsigned'}, {'name': 'name', 'type': 'string'}, {'name': 'setuid',
         'type': 'unsigned'}]]
@@ -821,7 +821,7 @@ box.space._space:select()
 ...
 box.space._func:select()
 ---
-- - [1, 1, 'box.schema.user.info', 1, 'LUA']
+- - [1, 1, 'box.schema.user.info', 1, 'LUA', '']
 ...
 session = nil
 ---
diff --git a/test/box/persistent_func.result b/test/box/persistent_func.result
new file mode 100644
index 000000000..ba544394e
--- /dev/null
+++ b/test/box/persistent_func.result
@@ -0,0 +1,163 @@
+env = require('test_run')
+---
+...
+test_run = env.new()
+---
+...
+--
+-- gh-4182: Add persistent LUA functions.
+--
+box.schema.user.grant('guest', 'execute', 'universe')
+---
+...
+net = require('net.box')
+---
+...
+conn = net.connect(box.cfg.listen)
+---
+...
+-- Test valid function.
+test_run:cmd("setopt delimiter ';'")
+---
+- true
+...
+lua_code = [[function(tuple)
+	if type(tuple.address) ~= 'string' then return nil, 'Invalid field type' end
+	local t = tuple.address:lower():split()
+	for k,v in pairs(t) do t[k] = {v} end
+	return t
+end
+]]
+test_run:cmd("setopt delimiter ''");
+---
+...
+box.schema.func.create('test', {lua_code = lua_code, language = "C"})
+---
+- error: 'Failed to create function ''test'': function lua_code may be specified only
+    for Lua language'
+...
+box.schema.func.create('test', {lua_code = lua_code})
+---
+...
+box.schema.func.exists('test')
+---
+- true
+...
+conn:call("test", {{address = "Moscow Dolgoprudny"}})
+---
+- [['moscow'], ['dolgoprudny']]
+...
+-- Test that monkey-patch attack is not possible.
+test_run:cmd("setopt delimiter ';'")
+---
+- true
+...
+lua_code_monkey = [[function(tuple)
+	math.abs = math.log
+	return tuple
+end
+]]
+test_run:cmd("setopt delimiter ''");
+---
+...
+box.schema.func.create('lua_code_monkey', {lua_code = lua_code_monkey})
+---
+...
+conn:call("lua_code_monkey", {{address = "Moscow Dolgoprudny"}})
+---
+- {'address': 'Moscow Dolgoprudny'}
+...
+math.abs(-666.666)
+---
+- 666.666
+...
+-- Test taht 'require' is forbidden.
+test_run:cmd("setopt delimiter ';'")
+---
+- true
+...
+lua_code_bad1 = [[function(tuple)
+	local json = require('json')
+	return json.encode(tuple)
+end
+]]
+test_run:cmd("setopt delimiter ''");
+---
+...
+box.schema.func.create('json_serializer', {lua_code = lua_code_bad1})
+---
+...
+conn:call("json_serializer", {{address = "Moscow Dolgoprudny"}})
+---
+- error: '[string "return function(tuple) ..."]:1: attempt to call global ''require''
+    (a nil value)'
+...
+-- Test function with spell error - case 1.
+test_run:cmd("setopt delimiter ';'")
+---
+- true
+...
+lua_code_bad2 = [[function(tuple)
+	ret tuple
+end
+]]
+test_run:cmd("setopt delimiter ''");
+---
+...
+box.schema.func.create('lua_code_bad2', {lua_code = lua_code_bad2})
+---
+- error: "Failed to dynamically load function 'lua_code_bad2': function(tuple) \tret
+    tuple end "
+...
+-- Test function with spell error - case 2.
+test_run:cmd("setopt delimiter ';'")
+---
+- true
+...
+lua_code_bad3 = [[func(tuple)
+	return tuple
+end
+]]
+test_run:cmd("setopt delimiter ''");
+---
+...
+box.schema.func.create('lua_code_bad3', {lua_code = lua_code_bad3})
+---
+- error: "Failed to dynamically load function 'lua_code_bad3': func(tuple) \treturn
+    tuple end "
+...
+conn:call("lua_code_bad3", {{address = "Moscow Dolgoprudny"}})
+---
+- error: Procedure 'lua_code_bad3' is not defined
+...
+conn:close()
+---
+...
+-- Restart server.
+test_run:cmd("restart server default")
+net = require('net.box')
+---
+...
+test_run = require('test_run').new()
+---
+...
+conn = net.connect(box.cfg.listen)
+---
+...
+conn:call("test", {{address = "Moscow Dolgoprudny"}})
+---
+- [['moscow'], ['dolgoprudny']]
+...
+conn:close()
+---
+...
+box.schema.func.drop('test')
+---
+...
+box.schema.func.exists('test')
+---
+- false
+...
+box.schema.user.revoke('guest', 'execute', 'universe')
+---
+...
diff --git a/test/box/persistent_func.test.lua b/test/box/persistent_func.test.lua
new file mode 100644
index 000000000..67a315197
--- /dev/null
+++ b/test/box/persistent_func.test.lua
@@ -0,0 +1,78 @@
+env = require('test_run')
+test_run = env.new()
+
+--
+-- gh-4182: Add persistent LUA functions.
+--
+box.schema.user.grant('guest', 'execute', 'universe')
+net = require('net.box')
+conn = net.connect(box.cfg.listen)
+
+-- Test valid function.
+test_run:cmd("setopt delimiter ';'")
+lua_code = [[function(tuple)
+	if type(tuple.address) ~= 'string' then return nil, 'Invalid field type' end
+	local t = tuple.address:lower():split()
+	for k,v in pairs(t) do t[k] = {v} end
+	return t
+end
+]]
+test_run:cmd("setopt delimiter ''");
+box.schema.func.create('test', {lua_code = lua_code, language = "C"})
+box.schema.func.create('test', {lua_code = lua_code})
+box.schema.func.exists('test')
+conn:call("test", {{address = "Moscow Dolgoprudny"}})
+
+-- Test that monkey-patch attack is not possible.
+test_run:cmd("setopt delimiter ';'")
+lua_code_monkey = [[function(tuple)
+	math.abs = math.log
+	return tuple
+end
+]]
+test_run:cmd("setopt delimiter ''");
+box.schema.func.create('lua_code_monkey', {lua_code = lua_code_monkey})
+conn:call("lua_code_monkey", {{address = "Moscow Dolgoprudny"}})
+math.abs(-666.666)
+
+-- Test taht 'require' is forbidden.
+test_run:cmd("setopt delimiter ';'")
+lua_code_bad1 = [[function(tuple)
+	local json = require('json')
+	return json.encode(tuple)
+end
+]]
+test_run:cmd("setopt delimiter ''");
+box.schema.func.create('json_serializer', {lua_code = lua_code_bad1})
+conn:call("json_serializer", {{address = "Moscow Dolgoprudny"}})
+
+-- Test function with spell error - case 1.
+test_run:cmd("setopt delimiter ';'")
+lua_code_bad2 = [[function(tuple)
+	ret tuple
+end
+]]
+test_run:cmd("setopt delimiter ''");
+box.schema.func.create('lua_code_bad2', {lua_code = lua_code_bad2})
+
+-- Test function with spell error - case 2.
+test_run:cmd("setopt delimiter ';'")
+lua_code_bad3 = [[func(tuple)
+	return tuple
+end
+]]
+test_run:cmd("setopt delimiter ''");
+box.schema.func.create('lua_code_bad3', {lua_code = lua_code_bad3})
+conn:call("lua_code_bad3", {{address = "Moscow Dolgoprudny"}})
+
+conn:close()
+-- Restart server.
+test_run:cmd("restart server default")
+net = require('net.box')
+test_run = require('test_run').new()
+conn = net.connect(box.cfg.listen)
+conn:call("test", {{address = "Moscow Dolgoprudny"}})
+conn:close()
+box.schema.func.drop('test')
+box.schema.func.exists('test')
+box.schema.user.revoke('guest', 'execute', 'universe')
-- 
2.21.0