[Tarantool-patches] [PATCH v5 0/3] Introduce _session_setting system space

[Tarantool-patches] [PATCH v5 0/3] Introduce _session_setting system space

[imeevma]

This patch-set creates _session_settings system space. This space
is used to view and change session settings.

https://github.com/tarantool/tarantool/issues/4511
https://github.com/tarantool/tarantool/tree/imeevma/gh-4511-new-engine

Mergen Imeev (3):
  box: introduce 'service' engine
  box: introduce _session_settings system space
  box: add SQL settings to _session_settings

 src/box/CMakeLists.txt                             |   2 +
 src/box/bootstrap.snap                             | Bin 5921 -> 5976 bytes
 src/box/box.cc                                     |   4 +
 src/box/errcode.h                                  |   3 +-
 src/box/lua/space.cc                               |   2 +
 src/box/lua/upgrade.lua                            |  15 +
 src/box/schema_def.h                               |   8 +
 src/box/service_engine.c                           | 135 ++++++
 src/box/service_engine.h                           |  53 +++
 src/box/session_settings.c                         | 472 +++++++++++++++++++++
 src/box/session_settings.h                         |  70 +++
 src/box/sql.c                                      |   5 +
 src/box/sql/build.c                                | 222 ++++++++++
 test/app-tap/tarantoolctl.test.lua                 |   4 +-
 test/box-py/bootstrap.result                       |   3 +
 test/box/access_sysview.result                     |   6 +-
 test/box/alter.result                              |   5 +-
 ...h-4511-access-settings-from-any-frontend.result | 273 ++++++++++++
 ...4511-access-settings-from-any-frontend.test.lua | 106 +++++
 test/box/misc.result                               |   1 +
 test/wal_off/alter.result                          |   2 +-
 21 files changed, 1382 insertions(+), 9 deletions(-)
 create mode 100644 src/box/service_engine.c
 create mode 100644 src/box/service_engine.h
 create mode 100644 src/box/session_settings.c
 create mode 100644 src/box/session_settings.h
 create mode 100644 test/box/gh-4511-access-settings-from-any-frontend.result
 create mode 100644 test/box/gh-4511-access-settings-from-any-frontend.test.lua

-- 
2.7.4

[Tarantool-patches] [PATCH v5 1/3] box: introduce 'service' engine

[imeevma]

This patch introduces a new engine called "service" that will be
used to create a new system space. The main idea of this engine is
that it will not have a predefined space_vtab. With this engine,
we can create unusual spaces with their own vtab and behavior.

Due to the nature of this engine, it can only be used to create
system spaces.

Part of #4511
---
 src/box/CMakeLists.txt                             |  1 +
 src/box/box.cc                                     |  4 +
 src/box/service_engine.c                           | 95 ++++++++++++++++++++++
 src/box/service_engine.h                           | 53 ++++++++++++
 ...h-4511-access-settings-from-any-frontend.result | 10 +++
 ...4511-access-settings-from-any-frontend.test.lua |  4 +
 6 files changed, 167 insertions(+)
 create mode 100644 src/box/service_engine.c
 create mode 100644 src/box/service_engine.h
 create mode 100644 test/box/gh-4511-access-settings-from-any-frontend.result
 create mode 100644 test/box/gh-4511-access-settings-from-any-frontend.test.lua

diff --git a/src/box/CMakeLists.txt b/src/box/CMakeLists.txt
index fc9d1a3..e0b5c55 100644
--- a/src/box/CMakeLists.txt
+++ b/src/box/CMakeLists.txt
@@ -79,6 +79,7 @@ add_library(box STATIC
     memtx_space.c
     sysview.c
     blackhole.c
+    service_engine.c
     vinyl.c
     vy_stmt.c
     vy_mem.c
diff --git a/src/box/box.cc b/src/box/box.cc
index b119c92..11ffead 100644
--- a/src/box/box.cc
+++ b/src/box/box.cc
@@ -53,6 +53,7 @@
 #include "memtx_engine.h"
 #include "sysview.h"
 #include "blackhole.h"
+#include "service_engine.h"
 #include "vinyl.h"
 #include "space.h"
 #include "index.h"
@@ -1693,6 +1694,9 @@ engine_init()
 	struct sysview_engine *sysview = sysview_engine_new_xc();
 	engine_register((struct engine *)sysview);
 
+	struct engine *service_engine = service_engine_new_xc();
+	engine_register(service_engine);
+
 	struct engine *blackhole = blackhole_engine_new_xc();
 	engine_register(blackhole);
 
diff --git a/src/box/service_engine.c b/src/box/service_engine.c
new file mode 100644
index 0000000..67f8422
--- /dev/null
+++ b/src/box/service_engine.c
@@ -0,0 +1,95 @@
+/*
+ * Copyright 2010-2019, Tarantool AUTHORS, please see AUTHORS file.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above
+ *    copyright notice, this list of conditions and the
+ *    following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+ * <COPYRIGHT HOLDER> OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+ * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include "service_engine.h"
+#include "schema.h"
+
+static void
+service_engine_shutdown(struct engine *engine)
+{
+	free(engine);
+}
+
+static struct space *
+service_engine_create_space(struct engine *engine, struct space_def *def,
+			    struct rlist *key_list)
+{
+	(void)engine;
+	(void)def;
+	(void)key_list;
+	/* There are currently no spaces with this engine. */
+	diag_set(ClientError, ER_UNSUPPORTED, "Tarantool",
+		 "spaces with 'service' engine.");
+	return NULL;
+}
+
+static const struct engine_vtab service_engine_vtab = {
+	/* .shutdown = */ service_engine_shutdown,
+	/* .create_space = */ service_engine_create_space,
+	/* .prepare_join = */ generic_engine_prepare_join,
+	/* .join = */ generic_engine_join,
+	/* .complete_join = */ generic_engine_complete_join,
+	/* .begin = */ generic_engine_begin,
+	/* .begin_statement = */ generic_engine_begin_statement,
+	/* .prepare = */ generic_engine_prepare,
+	/* .commit = */ generic_engine_commit,
+	/* .rollback_statement = */ generic_engine_rollback_statement,
+	/* .rollback = */ generic_engine_rollback,
+	/* .switch_to_ro = */ generic_engine_switch_to_ro,
+	/* .bootstrap = */ generic_engine_bootstrap,
+	/* .begin_initial_recovery = */ generic_engine_begin_initial_recovery,
+	/* .begin_final_recovery = */ generic_engine_begin_final_recovery,
+	/* .end_recovery = */ generic_engine_end_recovery,
+	/* .begin_checkpoint = */ generic_engine_begin_checkpoint,
+	/* .wait_checkpoint = */ generic_engine_wait_checkpoint,
+	/* .commit_checkpoint = */ generic_engine_commit_checkpoint,
+	/* .abort_checkpoint = */ generic_engine_abort_checkpoint,
+	/* .collect_garbage = */ generic_engine_collect_garbage,
+	/* .backup = */ generic_engine_backup,
+	/* .memory_stat = */ generic_engine_memory_stat,
+	/* .reset_stat = */ generic_engine_reset_stat,
+	/* .check_space_def = */ generic_engine_check_space_def,
+};
+
+struct engine *
+service_engine_new(void)
+{
+	struct engine *service_engine = calloc(1, sizeof(*service_engine));
+	if (service_engine == NULL) {
+		diag_set(OutOfMemory, sizeof(*service_engine), "calloc",
+			 "service_engine");
+		return NULL;
+	}
+
+	service_engine->vtab = &service_engine_vtab;
+	service_engine->name = "service";
+	service_engine->flags = ENGINE_BYPASS_TX;
+	return service_engine;
+}
diff --git a/src/box/service_engine.h b/src/box/service_engine.h
new file mode 100644
index 0000000..48e2518
--- /dev/null
+++ b/src/box/service_engine.h
@@ -0,0 +1,53 @@
+#pragma once
+/*
+ * Copyright 2010-2019, Tarantool AUTHORS, please see AUTHORS file.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above
+ *    copyright notice, this list of conditions and the
+ *    following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+ * <COPYRIGHT HOLDER> OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+ * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#if defined(__cplusplus)
+extern "C" {
+#endif /* defined(__cplusplus) */
+
+struct engine *
+service_engine_new(void);
+
+#if defined(__cplusplus)
+} /* extern "C" */
+
+#include "diag.h"
+
+static inline struct engine *
+service_engine_new_xc(void)
+{
+	struct engine *service_engine = service_engine_new();
+	if (service_engine == NULL)
+		diag_raise();
+	return service_engine;
+}
+
+#endif /* defined(__plusplus) */
diff --git a/test/box/gh-4511-access-settings-from-any-frontend.result b/test/box/gh-4511-access-settings-from-any-frontend.result
new file mode 100644
index 0000000..de8bcb7
--- /dev/null
+++ b/test/box/gh-4511-access-settings-from-any-frontend.result
@@ -0,0 +1,10 @@
+-- test-run result file version 2
+test_run = require('test_run').new()
+ | ---
+ | ...
+
+-- User cannot create spaces with this engine.
+s = box.schema.space.create('test', {engine = 'service'})
+ | ---
+ | - error: Tarantool does not support spaces with 'service' engine.
+ | ...
diff --git a/test/box/gh-4511-access-settings-from-any-frontend.test.lua b/test/box/gh-4511-access-settings-from-any-frontend.test.lua
new file mode 100644
index 0000000..e2d212d
--- /dev/null
+++ b/test/box/gh-4511-access-settings-from-any-frontend.test.lua
@@ -0,0 +1,4 @@
+test_run = require('test_run').new()
+
+-- User cannot create spaces with this engine.
+s = box.schema.space.create('test', {engine = 'service'})
-- 
2.7.4

[Tarantool-patches] [PATCH v5 2/3] box: introduce _session_settings system space

[imeevma]

This patch creates _session_settings system space. This space is
used to view and change session settings. This space is one of the
special spaces that have a "service" engine. The main idea of this
space is that it will not store tuples, but when you call the
get() or select() methods, it creates tuples on the fly. Because
of this, even if the same setting is asked, the returned tuples
will be different. In addition, this space allows you to change
the setting value using the update() method, in which case it
directly changes the setting value.

There are no settings at the moment, some will be added in the
next patch.

Part of #4511
---
 src/box/CMakeLists.txt                             |   1 +
 src/box/bootstrap.snap                             | Bin 5921 -> 5976 bytes
 src/box/lua/space.cc                               |   2 +
 src/box/lua/upgrade.lua                            |  15 +
 src/box/schema_def.h                               |   8 +
 src/box/service_engine.c                           |  54 ++-
 src/box/session_settings.c                         | 472 +++++++++++++++++++++
 src/box/session_settings.h                         |  69 +++
 test/app-tap/tarantoolctl.test.lua                 |   4 +-
 test/box-py/bootstrap.result                       |   3 +
 test/box/access_sysview.result                     |   6 +-
 test/box/alter.result                              |   5 +-
 ...h-4511-access-settings-from-any-frontend.result | 108 ++++-
 ...4511-access-settings-from-any-frontend.test.lua |  37 ++
 test/wal_off/alter.result                          |   2 +-
 15 files changed, 770 insertions(+), 16 deletions(-)
 create mode 100644 src/box/session_settings.c
 create mode 100644 src/box/session_settings.h

diff --git a/src/box/CMakeLists.txt b/src/box/CMakeLists.txt
index e0b5c55..e271182 100644
--- a/src/box/CMakeLists.txt
+++ b/src/box/CMakeLists.txt
@@ -80,6 +80,7 @@ add_library(box STATIC
     sysview.c
     blackhole.c
     service_engine.c
+    session_settings.c
     vinyl.c
     vy_stmt.c
     vy_mem.c
diff --git a/src/box/lua/space.cc b/src/box/lua/space.cc
index f6e96f0..01b58af 100644
--- a/src/box/lua/space.cc
+++ b/src/box/lua/space.cc
@@ -653,6 +653,8 @@ box_lua_space_init(struct lua_State *L)
 	lua_setfield(L, -2, "SPACE_SEQUENCE_ID");
 	lua_pushnumber(L, BOX_FUNC_INDEX_ID);
 	lua_setfield(L, -2, "FUNC_INDEX_ID");
+	lua_pushnumber(L, BOX_SESSION_SETTINGS_ID);
+	lua_setfield(L, -2, "SESSION_SETTINGS_ID");
 	lua_pushnumber(L, BOX_SYSTEM_ID_MIN);
 	lua_setfield(L, -2, "SYSTEM_ID_MIN");
 	lua_pushnumber(L, BOX_SYSTEM_ID_MAX);
diff --git a/src/box/lua/upgrade.lua b/src/box/lua/upgrade.lua
index 07f1e03..c69b6b5 100644
--- a/src/box/lua/upgrade.lua
+++ b/src/box/lua/upgrade.lua
@@ -951,8 +951,23 @@ local function drop_func_collation()
     _func.index.name:alter({parts = {{'name', 'string'}}})
 end
 
+local function create_session_settings_space()
+    local _space = box.space[box.schema.SPACE_ID]
+    local _index = box.space[box.schema.INDEX_ID]
+    local format = {}
+    format[1] = {name='name', type='string'}
+    format[2] = {name='value', type='any'}
+    log.info("create space _session_settings")
+    _space:insert{box.schema.SESSION_SETTINGS_ID, ADMIN, '_session_settings',
+                  'service', 2, {temporary = true}, format}
+    log.info("create index _session_settings:primary")
+    _index:insert{box.schema.SESSION_SETTINGS_ID, 0, 'primary', 'tree',
+                  {unique = true}, {{0, 'string'}}}
+end
+
 local function upgrade_to_2_3_1()
     drop_func_collation()
+    create_session_settings_space()
 end
 
 --------------------------------------------------------------------------------
diff --git a/src/box/schema_def.h b/src/box/schema_def.h
index ba870ff..f86cd42 100644
--- a/src/box/schema_def.h
+++ b/src/box/schema_def.h
@@ -114,6 +114,8 @@ enum {
 	BOX_CK_CONSTRAINT_ID = 364,
 	/** Space id of _func_index. */
 	BOX_FUNC_INDEX_ID = 372,
+	/** Space id of _session_settings. */
+	BOX_SESSION_SETTINGS_ID = 380,
 	/** End of the reserved range of system spaces. */
 	BOX_SYSTEM_ID_MAX = 511,
 	BOX_ID_NIL = 2147483647
@@ -277,6 +279,12 @@ enum {
 	BOX_FUNC_INDEX_FUNCTION_ID = 2,
 };
 
+/** _session_settings fields. */
+enum {
+	BOX_SESSION_SETTINGS_FIELD_NAME = 0,
+	BOX_SESSION_SETTINGS_FIELD_VALUE = 1,
+};
+
 /*
  * Different objects which can be subject to access
  * control.
diff --git a/src/box/service_engine.c b/src/box/service_engine.c
index 67f8422..5a33a73 100644
--- a/src/box/service_engine.c
+++ b/src/box/service_engine.c
@@ -29,8 +29,11 @@
  * SUCH DAMAGE.
  */
 #include "service_engine.h"
+#include "tuple.h"
 #include "schema.h"
 
+extern const struct space_vtab session_settings_space_vtab;
+
 static void
 service_engine_shutdown(struct engine *engine)
 {
@@ -41,13 +44,50 @@ static struct space *
 service_engine_create_space(struct engine *engine, struct space_def *def,
 			    struct rlist *key_list)
 {
-	(void)engine;
-	(void)def;
-	(void)key_list;
-	/* There are currently no spaces with this engine. */
-	diag_set(ClientError, ER_UNSUPPORTED, "Tarantool",
-		 "spaces with 'service' engine.");
-	return NULL;
+	/*
+	 * At the moment the only space that have this engine is
+	 * _session_sessings.
+	 */
+	if (def->id != BOX_SESSION_SETTINGS_ID) {
+		diag_set(ClientError, ER_UNSUPPORTED, "Tarantool",
+			 "non-system space with 'service' engine.");
+		return NULL;
+	}
+	const struct space_vtab *space_vtab = &session_settings_space_vtab;
+
+	struct space *space = (struct space *)calloc(1, sizeof(*space));
+	if (space == NULL) {
+		diag_set(OutOfMemory, sizeof(*space), "calloc", "space");
+		return NULL;
+	}
+	int key_count = 0;
+	struct key_def **keys = index_def_to_key_def(key_list, &key_count);
+	if (keys == NULL) {
+		free(space);
+		return NULL;
+	}
+	struct tuple_format *format =
+		tuple_format_new(&tuple_format_runtime->vtab, NULL, keys,
+				 key_count, def->fields, def->field_count,
+				 def->exact_field_count, def->dict,
+				 def->opts.is_temporary,
+				 def->opts.is_ephemeral);
+	if (format == NULL) {
+		free(space);
+		return NULL;
+	}
+	tuple_format_ref(format);
+	int rc = space_create(space, engine, space_vtab, def, key_list, format);
+	/*
+	 * Format is now referenced by the space if space has beed
+	 * created.
+	 */
+	tuple_format_unref(format);
+	if (rc != 0) {
+		free(space);
+		return NULL;
+	}
+	return space;
 }
 
 static const struct engine_vtab service_engine_vtab = {
diff --git a/src/box/session_settings.c b/src/box/session_settings.c
new file mode 100644
index 0000000..a969d3d
--- /dev/null
+++ b/src/box/session_settings.c
@@ -0,0 +1,472 @@
+/*
+ * Copyright 2010-2019, Tarantool AUTHORS, please see AUTHORS file.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above
+ *    copyright notice, this list of conditions and the
+ *    following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+ * <COPYRIGHT HOLDER> OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+ * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+#include "session_settings.h"
+#include "xrow_update.h"
+#include "service_engine.h"
+#include "column_mask.h"
+#include "session.h"
+#include "schema.h"
+#include "tuple.h"
+#include "xrow.h"
+#include "sql.h"
+
+struct session_setting_module
+	session_setting_modules[session_setting_type_MAX] = {};
+
+struct session_settings_index {
+	/** Base index. Must be the first member. */
+	struct index base;
+	/**
+	 * Format of the tuples iterators of this index return. It
+	 * is stored here so as not to lookup space each time to
+	 * get a format and create an iterator.
+	 */
+	struct tuple_format *format;
+};
+
+struct session_settings_iterator {
+	/** Base iterator. Must be the first member. */
+	struct iterator base;
+	/**
+	 * Format of the tuples this iterator returns. It is
+	 * stored here so as not to lookup space each time to get
+	 * a format for selected tuples.
+	 */
+	struct tuple_format *format;
+	/**
+	 * ID of the current session settings module in the global
+	 * list of the modules.
+	 */
+	int module_id;
+	/** ID of the setting in current module. */
+	int setting_id;
+	/** Decoded key. */
+	char *key;
+	/** True if the iterator returns only equal keys. */
+	bool is_eq;
+	/** True if the iterator should include equal keys. */
+	bool is_including;
+};
+
+static void
+session_settings_iterator_free(struct iterator *ptr)
+{
+	struct session_settings_iterator *it =
+		(struct session_settings_iterator *)ptr;
+	free(it->key);
+	free(it);
+}
+
+static int
+session_settings_next_in_module(const struct session_setting_module *module,
+				int *sid, const char *key, bool is_eq,
+				bool is_including)
+{
+	int i = *sid;
+	int count = module->setting_count;
+	if (i >= count)
+		return -1;
+	if (key == NULL)
+		return 0;
+	assert(i >= 0);
+	const char **name = &module->settings[i];
+	for (; i < count; ++i, ++name) {
+		int cmp = strcmp(*name, key);
+		if ((cmp == 0 && is_including) ||
+		    (cmp > 0 && !is_eq)) {
+			*sid = i;
+			return 0;
+		}
+	}
+	*sid = count;
+	return -1;
+}
+
+static int
+session_settings_prev_in_module(const struct session_setting_module *module,
+				int *sid, const char *key, bool is_eq,
+				bool is_including)
+{
+	int i = *sid;
+	int count = module->setting_count;
+	if (i < 0)
+		return -1;
+	if (key == NULL)
+		return 0;
+	if (i >= count)
+		i = count - 1;
+	const char **name = &module->settings[i];
+	for (; i >= 0; --i, --name) {
+		int cmp = strcmp(*name, key);
+		if ((cmp == 0 && is_including) ||
+		    (cmp < 0 && !is_eq)) {
+			*sid = i;
+			return 0;
+		}
+	}
+	*sid = -1;
+	return -1;
+}
+
+static int
+session_settings_iterator_next(struct iterator *iterator, struct tuple **result)
+{
+	struct session_settings_iterator *it =
+		(struct session_settings_iterator *)iterator;
+	int mid = it->module_id, sid = it->setting_id;
+	struct session_setting_module *module;
+	const char *key = it->key;
+	bool is_including = it->is_including, is_eq = it->is_eq;
+	bool is_found = false;
+	for (; mid < session_setting_type_MAX; ++mid, sid = 0) {
+		module = &session_setting_modules[mid];
+		if (session_settings_next_in_module(module, &sid, key, is_eq,
+						    is_including) == 0) {
+			is_found = true;
+			break;
+		}
+	}
+	it->module_id = mid;
+	it->setting_id = sid + 1;
+	if (!is_found) {
+		*result = NULL;
+		return 0;
+	}
+	const char *mp_pair, *mp_pair_end;
+	module->get(sid, &mp_pair, &mp_pair_end);
+	*result = box_tuple_new(it->format, mp_pair, mp_pair_end);
+	return *result != NULL ? 0 : -1;
+}
+
+static int
+session_settings_iterator_prev(struct iterator *iterator, struct tuple **result)
+{
+	struct session_settings_iterator *it =
+		(struct session_settings_iterator *)iterator;
+	int mid = it->module_id, sid = it->setting_id;
+	struct session_setting_module *module;
+	const char *key = it->key;
+	bool is_including = it->is_including, is_eq = it->is_eq;
+	bool is_found = false;
+	for (; mid >= 0; --mid, sid = INT_MAX) {
+		module = &session_setting_modules[mid];
+		if (session_settings_prev_in_module(module, &sid, key, is_eq,
+						    is_including) == 0) {
+			is_found = true;
+			break;
+		}
+	}
+	it->module_id = mid;
+	it->setting_id = sid - 1;
+	if (!is_found) {
+		*result = NULL;
+		return 0;
+	}
+	const char *mp_pair, *mp_pair_end;
+	module->get(sid, &mp_pair, &mp_pair_end);
+	*result = box_tuple_new(it->format, mp_pair, mp_pair_end);
+	return *result != NULL ? 0 : -1;
+}
+
+static void
+session_settings_index_destroy(struct index *index)
+{
+	free(index);
+}
+
+static struct iterator *
+session_settings_index_create_iterator(struct index *base,
+				       enum iterator_type type, const char *key,
+				       uint32_t part_count)
+{
+	struct session_settings_index *index =
+		(struct session_settings_index *)base;
+	char *decoded_key = NULL;
+	if (part_count > 0) {
+		assert(part_count == 1);
+		assert(mp_typeof(*key) == MP_STR);
+		uint32_t len;
+		const char *name = mp_decode_str(&key, &len);
+		decoded_key = (char *)malloc(len + 1);
+		if (decoded_key == NULL) {
+			diag_set(OutOfMemory, len + 1, "malloc", "decoded_key");
+			return NULL;
+		}
+		memcpy(decoded_key, name, len);
+		decoded_key[len] = '\0';
+	}
+	struct session_settings_iterator *it =
+		(struct session_settings_iterator *)malloc(sizeof(*it));
+	if (it == NULL) {
+		diag_set(OutOfMemory, sizeof(*it), "malloc", "it");
+		free(decoded_key);
+		return NULL;
+	}
+	iterator_create(&it->base, base);
+	it->base.free = session_settings_iterator_free;
+	it->key = decoded_key;
+	it->is_eq = type == ITER_EQ || type == ITER_REQ;
+	it->is_including = it->is_eq || type == ITER_GE || type == ITER_ALL ||
+			   type == ITER_LE;
+	it->format = index->format;
+	if (!iterator_type_is_reverse(type)) {
+		it->base.next = session_settings_iterator_next;
+		it->module_id = 0;
+		it->setting_id = 0;
+	} else {
+		it->base.next = session_settings_iterator_prev;
+		it->module_id = session_setting_type_MAX - 1;
+		struct session_setting_module *module =
+			&session_setting_modules[it->module_id];
+		it->setting_id = module->setting_count - 1;
+	}
+	return (struct iterator *)it;
+}
+
+static int
+session_settings_index_get(struct index *base, const char *key,
+			   uint32_t part_count, struct tuple **result)
+{
+	struct session_settings_index *index =
+		(struct session_settings_index *) base;
+	assert(part_count == 1);
+	(void) part_count;
+	uint32_t len;
+	key = mp_decode_str(&key, &len);
+	key = tt_cstr(key, len);
+	struct session_setting_module *module = &session_setting_modules[0];
+	struct session_setting_module *end = module + session_setting_type_MAX;
+	int sid = 0;
+	for (; module < end; ++module, sid = 0) {
+		if (session_settings_next_in_module(module, &sid, key, true,
+						    true) == 0)
+			goto found;
+	}
+	*result = NULL;
+	return 0;
+found:;
+	const char *mp_pair;
+	const char *mp_pair_end;
+	module->get(sid, &mp_pair, &mp_pair_end);
+	*result = box_tuple_new(index->format, mp_pair, mp_pair_end);
+	return *result != NULL ? 0 : -1;
+}
+
+static const struct index_vtab session_settings_index_vtab = {
+	/* .destroy = */ session_settings_index_destroy,
+	/* .commit_create = */ generic_index_commit_create,
+	/* .abort_create = */ generic_index_abort_create,
+	/* .commit_modify = */ generic_index_commit_modify,
+	/* .commit_drop = */ generic_index_commit_drop,
+	/* .update_def = */ generic_index_update_def,
+	/* .depends_on_pk = */ generic_index_depends_on_pk,
+	/* .def_change_requires_rebuild = */
+		generic_index_def_change_requires_rebuild,
+	/* .size = */ generic_index_size,
+	/* .bsize = */ generic_index_bsize,
+	/* .min = */ generic_index_min,
+	/* .max = */ generic_index_max,
+	/* .random = */ generic_index_random,
+	/* .count = */ generic_index_count,
+	/* .get = */ session_settings_index_get,
+	/* .replace = */ generic_index_replace,
+	/* .create_iterator = */ session_settings_index_create_iterator,
+	/* .create_snapshot_iterator = */
+		generic_index_create_snapshot_iterator,
+	/* .stat = */ generic_index_stat,
+	/* .compact = */ generic_index_compact,
+	/* .reset_stat = */ generic_index_reset_stat,
+	/* .begin_build = */ generic_index_begin_build,
+	/* .reserve = */ generic_index_reserve,
+	/* .build_next = */ generic_index_build_next,
+	/* .end_build = */ generic_index_end_build,
+};
+
+static void
+session_settings_space_destroy(struct space *space)
+{
+	free(space);
+}
+
+static int
+session_settings_space_execute_replace(struct space *space, struct txn *txn,
+				       struct request *request,
+				       struct tuple **result)
+{
+	(void)space;
+	(void)txn;
+	(void)request;
+	(void)result;
+	diag_set(ClientError, ER_UNSUPPORTED, "Session_settings space",
+		 "replace()");
+	return -1;
+}
+
+static int
+session_settings_space_execute_delete(struct space *space, struct txn *txn,
+				      struct request *request,
+				      struct tuple **result)
+{
+	(void)space;
+	(void)txn;
+	(void)request;
+	(void)result;
+	diag_set(ClientError, ER_UNSUPPORTED, "Session_settings space",
+		 "delete()");
+	return -1;
+}
+
+static int
+session_settings_space_execute_update(struct space *space, struct txn *txn,
+				      struct request *request,
+				      struct tuple **result)
+{
+	(void)txn;
+	struct tuple_format *format = space->format;
+	const char *old_data, *old_data_end, *new_data;
+	struct region *region = &fiber()->gc;
+	size_t used = region_used(region);
+	int rc = -1, sid = 0;
+	struct index_def *pk_def = space->index[0]->def;
+	uint64_t column_mask;
+
+	const char *new_key, *key = request->key;
+	uint32_t new_size, new_key_len, key_len = mp_decode_array(&key);
+	if (key_len == 0) {
+		diag_set(ClientError, ER_EXACT_MATCH, 1, 0);
+		return -1;
+	}
+	if (key_len > 1 || mp_typeof(*key) != MP_STR) {
+		diag_set(ClientError, ER_KEY_PART_TYPE, 0, "string");
+		return -1;
+	}
+	key = mp_decode_str(&key, &key_len);
+	key = tt_cstr(key, key_len);
+	struct session_setting_module *module = &session_setting_modules[0];
+	struct session_setting_module *end = module + session_setting_type_MAX;
+	for (; module < end; ++module, sid = 0) {
+		if (session_settings_next_in_module(module, &sid, key, true,
+						    true) == 0)
+			goto found;
+	}
+	*result = NULL;
+	return 0;
+found:
+	module->get(sid, &old_data, &old_data_end);
+	new_data = xrow_update_execute(request->tuple, request->tuple_end,
+				       old_data, old_data_end, format->dict,
+				       &new_size, request->index_base,
+				       &column_mask);
+	if (new_data == NULL)
+		goto finish;
+	*result = box_tuple_new(format, new_data, new_data + new_size);
+	if (*result == NULL)
+		goto finish;
+
+	mp_decode_array(&new_data);
+	new_key = mp_decode_str(&new_data, &new_key_len);
+	if (!key_update_can_be_skipped(pk_def->key_def->column_mask,
+				       column_mask)) {
+		if (key_len != new_key_len ||
+		    memcmp(key, new_key, key_len) != 0) {
+			diag_set(ClientError, ER_CANT_UPDATE_PRIMARY_KEY,
+				 pk_def->name, space_name(space));
+			goto finish;
+		}
+	}
+	if (module->set(sid, new_data) != 0)
+		goto finish;
+	rc = 0;
+finish:
+	region_truncate(region, used);
+	return rc;
+}
+
+static int
+session_settings_space_execute_upsert(struct space *space, struct txn *txn,
+				      struct request *request)
+{
+	(void)space;
+	(void)txn;
+	(void)request;
+	diag_set(ClientError, ER_UNSUPPORTED, "Session_settings space",
+		 "upsert()");
+	return -1;
+}
+
+static struct index *
+session_settings_space_create_index(struct space *space, struct index_def *def)
+{
+	assert(space->def->id == BOX_SESSION_SETTINGS_ID);
+	if (def->iid != 0) {
+		diag_set(ClientError, ER_UNSUPPORTED, "Session_settings space",
+			 "create_index()");
+		return NULL;
+	}
+
+	struct session_settings_index *index =
+		(struct session_settings_index *)calloc(1, sizeof(*index));
+	if (index == NULL) {
+		diag_set(OutOfMemory, sizeof(*index), "calloc", "index");
+		return NULL;
+	}
+	if (index_create(&index->base, space->engine,
+			 &session_settings_index_vtab, def) != 0) {
+		free(index);
+		return NULL;
+	}
+
+	index->format = space->format;
+	return &index->base;
+}
+
+const struct space_vtab session_settings_space_vtab = {
+	/* .destroy = */ session_settings_space_destroy,
+	/* .bsize = */ generic_space_bsize,
+	/* .execute_replace = */ session_settings_space_execute_replace,
+	/* .execute_delete = */ session_settings_space_execute_delete,
+	/* .execute_update = */ session_settings_space_execute_update,
+	/* .execute_upsert = */ session_settings_space_execute_upsert,
+	/* .ephemeral_replace = */ generic_space_ephemeral_replace,
+	/* .ephemeral_delete = */ generic_space_ephemeral_delete,
+	/* .ephemeral_rowid_next = */ generic_space_ephemeral_rowid_next,
+	/* .init_system_space = */ generic_init_system_space,
+	/* .init_ephemeral_space = */ generic_init_ephemeral_space,
+	/* .check_index_def = */ generic_space_check_index_def,
+	/* .create_index = */ session_settings_space_create_index,
+	/* .add_primary_key = */ generic_space_add_primary_key,
+	/* .drop_primary_key = */ generic_space_drop_primary_key,
+	/* .check_format = */ generic_space_check_format,
+	/* .build_index = */ generic_space_build_index,
+	/* .swap_index = */ generic_space_swap_index,
+	/* .prepare_alter = */ generic_space_prepare_alter,
+	/* .invalidate = */ generic_space_invalidate,
+};
diff --git a/src/box/session_settings.h b/src/box/session_settings.h
new file mode 100644
index 0000000..7415e0e
--- /dev/null
+++ b/src/box/session_settings.h
@@ -0,0 +1,69 @@
+#pragma once
+/*
+ * Copyright 2010-2019, Tarantool AUTHORS, please see AUTHORS file.
+ *
+ * Redistribution and use in source and binary forms, with or
+ * without modification, are permitted provided that the following
+ * conditions are met:
+ *
+ * 1. Redistributions of source code must retain the above
+ *    copyright notice, this list of conditions and the
+ *    following disclaimer.
+ *
+ * 2. Redistributions in binary form must reproduce the above
+ *    copyright notice, this list of conditions and the following
+ *    disclaimer in the documentation and/or other materials
+ *    provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY <COPYRIGHT HOLDER> ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL
+ * <COPYRIGHT HOLDER> OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT,
+ * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
+ * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
+ * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
+ * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+/**
+ * Session has settings. Settings belong to different subsystems,
+ * such as SQL. Each subsystem registers here its session setting
+ * type and a set of settings with getter and setter functions.
+ * The self-registration of modules allows session setting code
+ * not to depend on all the subsystems.
+ *
+ * The types should be ordered in alphabetical order, because the
+ * type list is used by setting iterators.
+ */
+enum session_setting_type {
+	session_setting_type_MAX,
+};
+
+struct session_setting_module {
+	/**
+	 * An array of setting names. All of them should have the
+	 * same prefix.
+	 */
+	const char **settings;
+	/** Count of settings. */
+	int setting_count;
+	/**
+	 * Get a MessagePack encoded pair [name, value] for a
+	 * setting having index @a id. Index is from the settings
+	 * array.
+	 */
+	void (*get)(int id, const char **mp_pair, const char **mp_pair_end);
+	/**
+	 * Set value of a setting by a given @a id from a
+	 * MessagePack encoded buffer. Note, it is not a pair, but
+	 * just value.
+	 */
+	int (*set)(int id, const char *mp_value);
+};
+
+extern struct session_setting_module session_setting_modules[];
diff --git a/test/app-tap/tarantoolctl.test.lua b/test/app-tap/tarantoolctl.test.lua
index 7a07860..4d70595 100755
--- a/test/app-tap/tarantoolctl.test.lua
+++ b/test/app-tap/tarantoolctl.test.lua
@@ -415,8 +415,8 @@ do
             check_ctlcat_xlog(test_i, dir, "--from=3 --to=6 --format=json --show-system --replica 1", "\n", 3)
             check_ctlcat_xlog(test_i, dir, "--from=3 --to=6 --format=json --show-system --replica 1 --replica 2", "\n", 3)
             check_ctlcat_xlog(test_i, dir, "--from=3 --to=6 --format=json --show-system --replica 2", "\n", 0)
-            check_ctlcat_snap(test_i, dir, "--space=280", "---\n", 24)
-            check_ctlcat_snap(test_i, dir, "--space=288", "---\n", 52)
+            check_ctlcat_snap(test_i, dir, "--space=280", "---\n", 25)
+            check_ctlcat_snap(test_i, dir, "--space=288", "---\n", 53)
         end)
     end)
 
diff --git a/test/box-py/bootstrap.result b/test/box-py/bootstrap.result
index 938a763..0876e77 100644
--- a/test/box-py/bootstrap.result
+++ b/test/box-py/bootstrap.result
@@ -96,6 +96,8 @@ box.space._space:select{}
         'type': 'boolean'}]]
   - [372, 1, '_func_index', 'memtx', 0, {}, [{'name': 'space_id', 'type': 'unsigned'},
       {'name': 'index_id', 'type': 'unsigned'}, {'name': 'func_id', 'type': 'unsigned'}]]
+  - [380, 1, '_session_settings', 'service', 2, {'temporary': true}, [{'name': 'name',
+        'type': 'string'}, {'name': 'value', 'type': 'any'}]]
 ...
 box.space._index:select{}
 ---
@@ -153,6 +155,7 @@ box.space._index:select{}
   - [364, 0, 'primary', 'tree', {'unique': true}, [[0, 'unsigned'], [1, 'string']]]
   - [372, 0, 'primary', 'tree', {'unique': true}, [[0, 'unsigned'], [1, 'unsigned']]]
   - [372, 1, 'fid', 'tree', {'unique': false}, [[2, 'unsigned']]]
+  - [380, 0, 'primary', 'tree', {'unique': true}, [[0, 'string']]]
 ...
 box.space._user:select{}
 ---
diff --git a/test/box/access_sysview.result b/test/box/access_sysview.result
index 1f33dec..799d19f 100644
--- a/test/box/access_sysview.result
+++ b/test/box/access_sysview.result
@@ -246,11 +246,11 @@ box.session.su('guest')
 ...
 #box.space._vspace:select{}
 ---
-- 25
+- 26
 ...
 #box.space._vindex:select{}
 ---
-- 53
+- 54
 ...
 #box.space._vuser:select{}
 ---
@@ -282,7 +282,7 @@ box.session.su('guest')
 ...
 #box.space._vindex:select{}
 ---
-- 53
+- 54
 ...
 #box.space._vuser:select{}
 ---
diff --git a/test/box/alter.result b/test/box/alter.result
index 9a2f991..f150faa 100644
--- a/test/box/alter.result
+++ b/test/box/alter.result
@@ -92,7 +92,7 @@ space = box.space[t[1]]
 ...
 space.id
 ---
-- 373
+- 381
 ...
 space.field_count
 ---
@@ -137,7 +137,7 @@ space_deleted
 ...
 space:replace{0}
 ---
-- error: Space '373' does not exist
+- error: Space '381' does not exist
 ...
 _index:insert{_space.id, 0, 'primary', 'tree', {unique=true}, {{0, 'unsigned'}}}
 ---
@@ -220,6 +220,7 @@ _index:select{}
   - [364, 0, 'primary', 'tree', {'unique': true}, [[0, 'unsigned'], [1, 'string']]]
   - [372, 0, 'primary', 'tree', {'unique': true}, [[0, 'unsigned'], [1, 'unsigned']]]
   - [372, 1, 'fid', 'tree', {'unique': false}, [[2, 'unsigned']]]
+  - [380, 0, 'primary', 'tree', {'unique': true}, [[0, 'string']]]
 ...
 -- modify indexes of a system space
 _index:delete{_index.id, 0}
diff --git a/test/box/gh-4511-access-settings-from-any-frontend.result b/test/box/gh-4511-access-settings-from-any-frontend.result
index de8bcb7..7acdd95 100644
--- a/test/box/gh-4511-access-settings-from-any-frontend.result
+++ b/test/box/gh-4511-access-settings-from-any-frontend.result
@@ -6,5 +6,111 @@ test_run = require('test_run').new()
 -- User cannot create spaces with this engine.
 s = box.schema.space.create('test', {engine = 'service'})
  | ---
- | - error: Tarantool does not support spaces with 'service' engine.
+ | - error: Tarantool does not support non-system space with 'service' engine.
+ | ...
+
+-- Check _session_settings space.
+s = box.space._session_settings
+ | ---
+ | ...
+s:format()
+ | ---
+ | - [{'name': 'name', 'type': 'string'}, {'name': 'value', 'type': 'any'}]
+ | ...
+
+-- Make sure that we cannot drop space.
+s:drop()
+ | ---
+ | - error: Can't drop the primary key in a system space, space '_session_settings'
+ | ...
+
+--
+-- Make sure, that session_settings space doesn't support
+-- create_index(), insert(), replace() and delete() methods.
+--
+s:create_index('a')
+ | ---
+ | - error: Session_settings space does not support create_index()
+ | ...
+s:insert({'a', 1})
+ | ---
+ | - error: Session_settings space does not support replace()
+ | ...
+s:delete({'b'})
+ | ---
+ | - error: Session_settings space does not support delete()
+ | ...
+s:replace({'sql_defer_foreign_keys', true})
+ | ---
+ | - error: Session_settings space does not support replace()
+ | ...
+
+-- Check get() and select(). They should return nothing for now.
+s:get({'a'})
+ | ---
+ | ...
+s:select()
+ | ---
+ | - []
+ | ...
+s:select({}, {iterator='EQ'})
+ | ---
+ | - []
+ | ...
+s:select({}, {iterator='ALL'})
+ | ---
+ | - []
+ | ...
+s:select({}, {iterator='GE'})
+ | ---
+ | - []
+ | ...
+s:select({}, {iterator='GT'})
+ | ---
+ | - []
+ | ...
+s:select({}, {iterator='REQ'})
+ | ---
+ | - []
+ | ...
+s:select({}, {iterator='LE'})
+ | ---
+ | - []
+ | ...
+s:select({}, {iterator='LT'})
+ | ---
+ | - []
+ | ...
+s:select({'a'}, {iterator='EQ'})
+ | ---
+ | - []
+ | ...
+s:select({'a'}, {iterator='ALL'})
+ | ---
+ | - []
+ | ...
+s:select({'a'}, {iterator='GE'})
+ | ---
+ | - []
+ | ...
+s:select({'a'}, {iterator='GT'})
+ | ---
+ | - []
+ | ...
+s:select({'a'}, {iterator='REQ'})
+ | ---
+ | - []
+ | ...
+s:select({'a'}, {iterator='LE'})
+ | ---
+ | - []
+ | ...
+s:select({'a'}, {iterator='LT'})
+ | ---
+ | - []
+ | ...
+
+-- Currently there is nothing to update, but update() should work.
+s:update('some_option', {{'=', 'value', true}})
+ | ---
  | ...
diff --git a/test/box/gh-4511-access-settings-from-any-frontend.test.lua b/test/box/gh-4511-access-settings-from-any-frontend.test.lua
index e2d212d..d27fec3 100644
--- a/test/box/gh-4511-access-settings-from-any-frontend.test.lua
+++ b/test/box/gh-4511-access-settings-from-any-frontend.test.lua
@@ -2,3 +2,40 @@ test_run = require('test_run').new()
 
 -- User cannot create spaces with this engine.
 s = box.schema.space.create('test', {engine = 'service'})
+
+-- Check _session_settings space.
+s = box.space._session_settings
+s:format()
+
+-- Make sure that we cannot drop space.
+s:drop()
+
+--
+-- Make sure, that session_settings space doesn't support
+-- create_index(), insert(), replace() and delete() methods.
+--
+s:create_index('a')
+s:insert({'a', 1})
+s:delete({'b'})
+s:replace({'sql_defer_foreign_keys', true})
+
+-- Check get() and select(). They should return nothing for now.
+s:get({'a'})
+s:select()
+s:select({}, {iterator='EQ'})
+s:select({}, {iterator='ALL'})
+s:select({}, {iterator='GE'})
+s:select({}, {iterator='GT'})
+s:select({}, {iterator='REQ'})
+s:select({}, {iterator='LE'})
+s:select({}, {iterator='LT'})
+s:select({'a'}, {iterator='EQ'})
+s:select({'a'}, {iterator='ALL'})
+s:select({'a'}, {iterator='GE'})
+s:select({'a'}, {iterator='GT'})
+s:select({'a'}, {iterator='REQ'})
+s:select({'a'}, {iterator='LE'})
+s:select({'a'}, {iterator='LT'})
+
+-- Currently there is nothing to update, but update() should work.
+s:update('some_option', {{'=', 'value', true}})
diff --git a/test/wal_off/alter.result b/test/wal_off/alter.result
index 62cb11d..97f7e6f 100644
--- a/test/wal_off/alter.result
+++ b/test/wal_off/alter.result
@@ -28,7 +28,7 @@ end;
 ...
 #spaces;
 ---
-- 65502
+- 65501
 ...
 -- cleanup
 for k, v in pairs(spaces) do
-- 
2.7.4

[Tarantool-patches] [PATCH v5 3/3] box: add SQL settings to _session_settings

[imeevma]

Part of #4511

@TarantoolBot document
Title: _session_settings system space
The _session_settings system space used to view or change session
settings.

This space uses a new engine. This allows us to create tuples on
the fly when the get() or select() methods are called. This
engine does not support the insert(), replace(), and delete()
methods. The only way to change the setting value is update(),
which can only be used with the "=" operation.

Because space creates a tuple on the fly, it allows us to get a
tuple without saving it anywhere. But this means that every time
we get a tuple from this system space, it is a new tuple, even if
they look the same:

tarantool> s = box.space._session_settings
tarantool> name = 'sql_default_engine'
tarantool> s:get({name}) == s:get({name})
---
- false
...

Currently, this space contains only SQL settings, since the only
session settings are SQL settings.

List of currently available session settings:

sql_default_engine
sql_defer_foreign_keys
sql_full_column_names
sql_recursive_triggers
sql_reverse_unordered_selects

Debug build also have debug settings that could be obtained from
this sysview:

sql_parser_trace
sql_select_trace
sql_trace
sql_vdbe_addoptrace
sql_vdbe_debug
sql_vdbe_eqp
sql_vdbe_listing
sql_vdbe_trace
sql_where_trace

Example of usage:
tarantool> s = box.space._session_settings
-- View session settings values.
tarantool> s:get({'sql_default_engine'})
---
- ['sql_default_engine', 'memtx']
...

tarantool> s:select()
---
- - ['sql_default_engine', 'memtx']
  - ['sql_defer_foreign_keys', false]
  - ['sql_full_column_names', false]
  - ['sql_recursive_triggers', true]
  - ['sql_reverse_unordered_selects', false]
...

tarantool> s:select('sql_g', {iterator='LE'})
---
- - ['sql_full_column_names', false]
  - ['sql_defer_foreign_keys', false]
  - ['sql_default_engine', 'memtx']
...

-- Change session setting value.
tarantool> s:update('sql_default_engine', {{'=', 'value', 'vinyl'}})
---
- ['sql_default_engine', 'vinyl']
...
---
 src/box/errcode.h                                  |   3 +-
 src/box/session_settings.h                         |   1 +
 src/box/sql.c                                      |   5 +
 src/box/sql/build.c                                | 222 ++++++++++++++++++++
 ...h-4511-access-settings-from-any-frontend.result | 225 +++++++++++++++++----
 ...4511-access-settings-from-any-frontend.test.lua | 105 ++++++++--
 test/box/misc.result                               |   1 +
 7 files changed, 507 insertions(+), 55 deletions(-)

diff --git a/src/box/errcode.h b/src/box/errcode.h
index 0eddc0b..740f5cf 100644
--- a/src/box/errcode.h
+++ b/src/box/errcode.h
@@ -258,7 +258,8 @@ struct errcode_record {
 	/*203 */_(ER_BOOTSTRAP_READONLY,	"Trying to bootstrap a local read-only instance as master") \
 	/*204 */_(ER_SQL_FUNC_WRONG_RET_COUNT,	"SQL expects exactly one argument returned from %s, got %d")\
 	/*205 */_(ER_FUNC_INVALID_RETURN_TYPE,	"Function '%s' returned value of invalid type: expected %s got %s") \
-	/*186 */_(ER_SQL_PARSER_GENERIC_WITH_POS,"At line %d at or near position %d: %s") \
+	/*206 */_(ER_SQL_PARSER_GENERIC_WITH_POS,"At line %d at or near position %d: %s") \
+	/*207 */_(ER_SESSION_SETTING_INVALID_VALUE,	"Session setting %s expected a value of type %s") \
 
 /*
  * !IMPORTANT! Please follow instructions at start of the file
diff --git a/src/box/session_settings.h b/src/box/session_settings.h
index 7415e0e..25490a7 100644
--- a/src/box/session_settings.h
+++ b/src/box/session_settings.h
@@ -41,6 +41,7 @@
  * type list is used by setting iterators.
  */
 enum session_setting_type {
+	SESSION_SETTING_SQL,
 	session_setting_type_MAX,
 };
 
diff --git a/src/box/sql.c b/src/box/sql.c
index f1df555..cc82617 100644
--- a/src/box/sql.c
+++ b/src/box/sql.c
@@ -64,9 +64,14 @@ static const uint32_t default_sql_flags = SQL_ShortColNames
 					  | SQL_AutoIndex
 					  | SQL_RecTriggers;
 
+extern void
+sql_session_settings_init();
+
 void
 sql_init()
 {
+	sql_session_settings_init();
+
 	default_flags |= default_sql_flags;
 
 	current_session()->sql_flags |= default_sql_flags;
diff --git a/src/box/sql/build.c b/src/box/sql/build.c
index a2862b5..8c9b38d 100644
--- a/src/box/sql/build.c
+++ b/src/box/sql/build.c
@@ -57,6 +57,7 @@
 #include "box/tuple_format.h"
 #include "box/coll_id_cache.h"
 #include "box/user.h"
+#include "box/session_settings.h"
 
 void
 sql_finish_coding(struct Parse *parse_context)
@@ -3297,3 +3298,224 @@ sql_fieldno_by_name(struct Parse *parse_context, struct Expr *field_name,
 	*fieldno = i;
 	return 0;
 }
+
+/**
+ * Identifiers of all SQL session setings. The identifier of the
+ * option is equal to its place in the sorted list of session
+ * options of current module.
+ *
+ * It is IMPORTANT that these options are sorted by name. If this
+ * is not the case, the result returned by the _session_settings
+ * space iterator will not be sorted properly.
+ */
+enum {
+	SQL_SESSION_SETTING_DEFAULT_ENGINE = 0,
+	SQL_SESSION_SETTING_DEFER_FOREIGN_KEYS,
+	SQL_SESSION_SETTING_FULL_COLUMN_NAMES,
+	SQL_SESSION_SETTING_FULL_METADATA,
+#ifndef NDEBUG
+	SQL_SESSION_SETTING_PARSER_TRACE,
+#endif
+	SQL_SESSION_SETTING_RECURSIVE_TRIGGERS,
+	SQL_SESSION_SETTING_REVERSE_UNORDERED_SELECTS,
+#ifndef NDEBUG
+	SQL_SESSION_SETTING_SELECT_TRACE,
+	SQL_SESSION_SETTING_TRACE,
+	SQL_SESSION_SETTING_VDBE_ADDOPTRACE,
+	SQL_SESSION_SETTING_VDBE_DEBUG,
+	SQL_SESSION_SETTING_VDBE_EQP,
+	SQL_SESSION_SETTING_VDBE_LISTING,
+	SQL_SESSION_SETTING_VDBE_TRACE,
+	SQL_SESSION_SETTING_WHERE_TRACE,
+#endif
+	sql_session_setting_MAX,
+};
+
+static const char *sql_session_setting_strs[sql_session_setting_MAX] = {
+	"sql_default_engine",
+	"sql_defer_foreign_keys",
+	"sql_full_column_names",
+	"sql_full_metadata",
+#ifndef NDEBUG
+	"sql_parser_trace",
+#endif
+	"sql_recursive_triggers",
+	"sql_reverse_unordered_selects",
+#ifndef NDEBUG
+	"sql_select_trace",
+	"sql_trace",
+	"sql_vdbe_addoptrace",
+	"sql_vdbe_debug",
+	"sql_vdbe_eqp",
+	"sql_vdbe_listing",
+	"sql_vdbe_trace",
+	"sql_where_trace",
+#endif
+};
+
+/**
+ * A local structure that allows to establish a connection between
+ * parameter and its field type and mask, if it has one.
+ */
+struct sql_option_metadata
+{
+	uint32_t field_type;
+	uint32_t mask;
+};
+
+/**
+ * Variable that contains SQL session option field types and masks
+ * if they have one or 0 if don't have.
+ *
+ * It is IMPORTANT that these options sorted by name.
+ */
+static struct sql_option_metadata sql_session_opts[] = {
+	/** SQL_SESSION_SETTING_DEFAULT_ENGINE */
+	{FIELD_TYPE_STRING, 0},
+	/** SQL_SESSION_SETTING_DEFER_FOREIGN_KEYS */
+	{FIELD_TYPE_BOOLEAN, SQL_DeferFKs},
+	/** SQL_SESSION_SETTING_FULL_COLUMN_NAMES */
+	{FIELD_TYPE_BOOLEAN, SQL_FullColNames},
+	/** SQL_SESSION_SETTING_FULL_METADATA */
+	{FIELD_TYPE_BOOLEAN, SQL_FullMetadata},
+#ifndef NDEBUG
+	/** SQL_SESSION_SETTING_PARSER_TRACE */
+	{FIELD_TYPE_BOOLEAN, PARSER_TRACE_FLAG},
+#endif
+	/** SQL_SESSION_SETTING_RECURSIVE_TRIGGERS */
+	{FIELD_TYPE_BOOLEAN, SQL_RecTriggers},
+	/** SQL_SESSION_SETTING_REVERSE_UNORDERED_SELECTS */
+	{FIELD_TYPE_BOOLEAN, SQL_ReverseOrder},
+#ifndef NDEBUG
+	/** SQL_SESSION_SETTING_SELECT_TRACE */
+	{FIELD_TYPE_BOOLEAN, SQL_SelectTrace},
+	/** SQL_SESSION_SETTING_TRACE */
+	{FIELD_TYPE_BOOLEAN, SQL_SqlTrace},
+	/** SQL_SESSION_SETTING_VDBE_ADDOPTRACE */
+	{FIELD_TYPE_BOOLEAN, SQL_VdbeAddopTrace},
+	/** SQL_SESSION_SETTING_VDBE_DEBUG */
+	{FIELD_TYPE_BOOLEAN,
+	 SQL_SqlTrace | SQL_VdbeListing | SQL_VdbeTrace},
+	/** SQL_SESSION_SETTING_VDBE_EQP */
+	{FIELD_TYPE_BOOLEAN, SQL_VdbeEQP},
+	/** SQL_SESSION_SETTING_VDBE_LISTING */
+	{FIELD_TYPE_BOOLEAN, SQL_VdbeListing},
+	/** SQL_SESSION_SETTING_VDBE_TRACE */
+	{FIELD_TYPE_BOOLEAN, SQL_VdbeTrace},
+	/** SQL_SESSION_SETTING_WHERE_TRACE */
+	{FIELD_TYPE_BOOLEAN, SQL_WhereTrace},
+#endif
+};
+
+static void
+sql_session_setting_get(int id, const char **mp_pair, const char **mp_pair_end)
+{
+	assert(id >= 0 && id < sql_session_setting_MAX);
+	struct session *session = current_session();
+	uint32_t flags = session->sql_flags;
+	struct sql_option_metadata *opt = &sql_session_opts[id];
+	uint32_t mask = opt->mask;
+	const char *name = sql_session_setting_strs[id];
+	size_t name_len = strlen(name);
+	size_t engine_len;
+	const char *engine;
+	size_t size = mp_sizeof_array(2) + mp_sizeof_str(name_len);
+	/*
+	 * Currently, SQL session settings are of a boolean or
+	 * string type.
+	 */
+	bool is_bool = opt->field_type == FIELD_TYPE_BOOLEAN;
+	if (is_bool) {
+		size += mp_sizeof_bool(true);
+	} else {
+		assert(id == SQL_SESSION_SETTING_DEFAULT_ENGINE);
+		engine = sql_storage_engine_strs[session->sql_default_engine];
+		engine_len = strlen(engine);
+		size += mp_sizeof_str(engine_len);
+	}
+
+	char *pos = static_alloc(size);
+	assert(pos != NULL);
+	char *pos_end = mp_encode_array(pos, 2);
+	pos_end = mp_encode_str(pos_end, name, name_len);
+	if (is_bool)
+		pos_end = mp_encode_bool(pos_end, (flags & mask) == mask);
+	else
+		pos_end = mp_encode_str(pos_end, engine, engine_len);
+	*mp_pair = pos;
+	*mp_pair_end = pos_end;
+}
+
+static int
+sql_set_boolean_option(int id, bool value)
+{
+	struct session *session = current_session();
+	struct sql_option_metadata *option = &sql_session_opts[id];
+	assert(option->field_type == FIELD_TYPE_BOOLEAN);
+	if (value)
+		session->sql_flags |= option->mask;
+	else
+		session->sql_flags &= ~option->mask;
+#ifndef NDEBUG
+	if (id == SQL_SESSION_SETTING_PARSER_TRACE) {
+		if (value)
+			sqlParserTrace(stdout, "parser: ");
+		else
+			sqlParserTrace(NULL, NULL);
+	}
+#endif
+	return 0;
+}
+
+static int
+sql_set_string_option(int id, const char *value)
+{
+	assert(sql_session_opts[id].field_type = FIELD_TYPE_STRING);
+	assert(id == SQL_SESSION_SETTING_DEFAULT_ENGINE);
+	(void)id;
+	enum sql_storage_engine engine = STR2ENUM(sql_storage_engine, value);
+	if (engine == sql_storage_engine_MAX) {
+		diag_set(ClientError, ER_NO_SUCH_ENGINE, value);
+		return -1;
+	}
+	current_session()->sql_default_engine = engine;
+	return 0;
+}
+
+static int
+sql_session_setting_set(int id, const char *mp_value)
+{
+	assert(id >= 0 && id < sql_session_setting_MAX);
+	enum mp_type mtype = mp_typeof(*mp_value);
+	enum field_type stype = sql_session_opts[id].field_type;
+	uint32_t len;
+	const char *tmp;
+	switch(stype) {
+	case FIELD_TYPE_BOOLEAN:
+		if (mtype != MP_BOOL)
+			break;
+		return sql_set_boolean_option(id, mp_decode_bool(&mp_value));
+	case FIELD_TYPE_STRING:
+		if (mtype != MP_STR)
+			break;
+		tmp = mp_decode_str(&mp_value, &len);
+		tmp = tt_cstr(tmp, len);
+		return sql_set_string_option(id, tmp);
+	default:
+		unreachable();
+	}
+	diag_set(ClientError, ER_SESSION_SETTING_INVALID_VALUE,
+		 sql_session_setting_strs[id], field_type_strs[stype]);
+	return -1;
+}
+
+void
+sql_session_settings_init()
+{
+	struct session_setting_module *module =
+		&session_setting_modules[SESSION_SETTING_SQL];
+	module->settings = sql_session_setting_strs;
+	module->setting_count = sql_session_setting_MAX;
+	module->get = sql_session_setting_get;
+	module->set = sql_session_setting_set;
+}
diff --git a/test/box/gh-4511-access-settings-from-any-frontend.result b/test/box/gh-4511-access-settings-from-any-frontend.result
index 7acdd95..b021c29 100644
--- a/test/box/gh-4511-access-settings-from-any-frontend.result
+++ b/test/box/gh-4511-access-settings-from-any-frontend.result
@@ -45,72 +45,229 @@ s:replace({'sql_defer_foreign_keys', true})
  | - error: Session_settings space does not support replace()
  | ...
 
--- Check get() and select(). They should return nothing for now.
-s:get({'a'})
+--
+-- Check select() method of session_settings space. Should work
+-- the same way as an ordinary space with an index of the type
+-- "TREE".
+--
+t = box.schema.space.create('settings', {format = s:format()})
+ | ---
+ | ...
+_ = t:create_index('primary')
+ | ---
+ | ...
+for _,value in s:pairs() do t:insert(value) end
+ | ---
+ | ...
+
+test_run:cmd('setopt delimiter ";"')
+ | ---
+ | - true
+ | ...
+function check_sorting(ss, ts, key)
+    local iterators_list = {'ALL', 'REQ', 'EQ', 'GE', 'GT', 'LE', 'LT'}
+    for _, it in pairs(iterators_list) do
+        local view_space = ss:select({key}, {iterator = it})
+        local test_space = ts:select({key}, {iterator = it})
+        for key, value in pairs(view_space) do
+            if test_space[key].name ~= value.name then
+                return {
+                    err = 'bad sorting', type = it,
+                    exp = test_space[key].name, got = value.name
+                }
+            end
+        end
+    end
+end;
  | ---
  | ...
-s:select()
+test_run:cmd('setopt delimiter ""');
  | ---
- | - []
+ | - true
  | ...
-s:select({}, {iterator='EQ'})
+
+check_sorting(s, t)
  | ---
- | - []
  | ...
-s:select({}, {iterator='ALL'})
+check_sorting(s, t, 'abcde')
  | ---
- | - []
  | ...
-s:select({}, {iterator='GE'})
+check_sorting(s, t, 'sql_d')
  | ---
- | - []
  | ...
-s:select({}, {iterator='GT'})
+check_sorting(s, t, 'sql_v')
  | ---
- | - []
  | ...
-s:select({}, {iterator='REQ'})
+check_sorting(s, t, 'sql_defer_foreign_keys')
  | ---
- | - []
  | ...
-s:select({}, {iterator='LE'})
+
+t:drop()
  | ---
- | - []
  | ...
-s:select({}, {iterator='LT'})
+
+-- Check get() method of session_settings space.
+s:get({'sql_defer_foreign_keys'})
  | ---
- | - []
+ | - ['sql_defer_foreign_keys', false]
  | ...
-s:select({'a'}, {iterator='EQ'})
+s:get({'sql_recursive_triggers'})
  | ---
- | - []
+ | - ['sql_recursive_triggers', true]
  | ...
-s:select({'a'}, {iterator='ALL'})
+s:get({'sql_reverse_unordered_selects'})
  | ---
- | - []
+ | - ['sql_reverse_unordered_selects', false]
  | ...
-s:select({'a'}, {iterator='GE'})
+s:get({'sql_default_engine'})
  | ---
- | - []
+ | - ['sql_default_engine', 'memtx']
  | ...
-s:select({'a'}, {iterator='GT'})
+s:get({'abcd'})
  | ---
- | - []
  | ...
-s:select({'a'}, {iterator='REQ'})
+
+-- Check pairs() method of session_settings space.
+t = {}
  | ---
- | - []
  | ...
-s:select({'a'}, {iterator='LE'})
+for key, value in s:pairs() do table.insert(t, {key, value}) end
  | ---
- | - []
  | ...
-s:select({'a'}, {iterator='LT'})
+#t == s:count()
  | ---
- | - []
+ | - true
  | ...
 
--- Currently there is nothing to update, but update() should work.
-s:update('some_option', {{'=', 'value', true}})
+-- Check update() method of session_settings space.
+
+-- Correct updates.
+s:update('sql_defer_foreign_keys', {{'=', 'value', true}})
+ | ---
+ | - ['sql_defer_foreign_keys', true]
+ | ...
+s:update({'sql_defer_foreign_keys'}, {{'=', 2, false}})
+ | ---
+ | - ['sql_defer_foreign_keys', false]
+ | ...
+s:update('sql_default_engine', {{'=', 2, 'vinyl'}})
+ | ---
+ | - ['sql_default_engine', 'vinyl']
+ | ...
+s:update('sql_default_engine', {{':', 'value', 1, 5, 'memtx'}})
+ | ---
+ | - ['sql_default_engine', 'memtx']
+ | ...
+s:update('a', {{'=', 2, 1}})
+ | ---
+ | ...
+
+-- Inorrect updates.
+s:update({{'sql_defer_foreign_keys'}}, {{'=', 'value', true}})
+ | ---
+ | - error: 'Supplied key type of part 0 does not match index part type: expected string'
+ | ...
+
+s:update('sql_defer_foreign_keys', {'=', 'value', true})
+ | ---
+ | - error: Illegal parameters, update operation must be an array {op,..}
+ | ...
+s:update('sql_defer_foreign_keys', {{'=', 'value', true}, {'=', 2, true}})
+ | ---
+ | - ['sql_defer_foreign_keys', true]
+ | ...
+s:update('sql_defer_foreign_keys', {{}})
+ | ---
+ | - error: Illegal parameters, update operation must be an array {op,..}, got empty
+ |     array
+ | ...
+s:update('sql_defer_foreign_keys', {{'='}})
+ | ---
+ | - error: Unknown UPDATE operation
+ | ...
+s:update('sql_defer_foreign_keys', {{'=', 'value'}})
+ | ---
+ | - error: Unknown UPDATE operation
+ | ...
+s:update('sql_defer_foreign_keys', {{'=', 'value', true, 1}})
+ | ---
+ | - error: Unknown UPDATE operation
+ | ...
+
+s:update('sql_defer_foreign_keys', {{'+', 'value', 2}})
+ | ---
+ | - error: 'Argument type in operation ''+'' on field ''value'' does not match field
+ |     type: expected a number'
+ | ...
+s:update('sql_defer_foreign_keys', {{'-', 'value', 2}})
+ | ---
+ | - error: 'Argument type in operation ''-'' on field ''value'' does not match field
+ |     type: expected a number'
+ | ...
+s:update('sql_defer_foreign_keys', {{'&', 'value', 2}})
+ | ---
+ | - error: 'Argument type in operation ''&'' on field ''value'' does not match field
+ |     type: expected a positive integer'
+ | ...
+s:update('sql_defer_foreign_keys', {{'|', 'value', 2}})
+ | ---
+ | - error: 'Argument type in operation ''|'' on field ''value'' does not match field
+ |     type: expected a positive integer'
+ | ...
+s:update('sql_defer_foreign_keys', {{'^', 'value', 2}})
+ | ---
+ | - error: 'Argument type in operation ''^'' on field ''value'' does not match field
+ |     type: expected a positive integer'
+ | ...
+s:update('sql_defer_foreign_keys', {{'!', 'value', 2}})
+ | ---
+ | - error: Tuple field count 3 does not match space field count 2
+ | ...
+s:update('sql_defer_foreign_keys', {{'#', 'value', 2}})
+ | ---
+ | - error: Tuple field count 1 does not match space field count 2
+ | ...
+s:update('sql_defer_foreign_keys', {{1, 'value', true}})
+ | ---
+ | - error: Illegal parameters, update operation name must be a string
+ | ...
+s:update('sql_defer_foreign_keys', {{{1}, 'value', true}})
+ | ---
+ | - error: Illegal parameters, update operation name must be a string
+ | ...
+
+s:update('sql_defer_foreign_keys', {{'=', {'value'}, true}})
+ | ---
+ | - error: Illegal parameters, field id must be a number or a string
+ | ...
+s:update('sql_defer_foreign_keys', {{'=', 1, 'new_key'}})
+ | ---
+ | - error: Attempt to modify a tuple field which is part of index 'primary' in space
+ |     '_session_settings'
+ | ...
+s:update('sql_defer_foreign_keys', {{'=', 'name', 'new_key'}})
+ | ---
+ | - error: Attempt to modify a tuple field which is part of index 'primary' in space
+ |     '_session_settings'
+ | ...
+s:update('sql_defer_foreign_keys', {{'=', 3, true}})
+ | ---
+ | - error: Tuple field count 3 does not match space field count 2
+ | ...
+s:update('sql_defer_foreign_keys', {{'=', 'some text', true}})
+ | ---
+ | - error: Field 'some text' was not found in the tuple
+ | ...
+
+s:update('sql_defer_foreign_keys', {{'=', 'value', 1}})
+ | ---
+ | - error: Session setting sql_defer_foreign_keys expected a value of type boolean
+ | ...
+s:update('sql_defer_foreign_keys', {{'=', 'value', {1}}})
+ | ---
+ | - error: Session setting sql_defer_foreign_keys expected a value of type boolean
+ | ...
+s:update('sql_defer_foreign_keys', {{'=', 'value', '1'}})
  | ---
+ | - error: Session setting sql_defer_foreign_keys expected a value of type boolean
  | ...
diff --git a/test/box/gh-4511-access-settings-from-any-frontend.test.lua b/test/box/gh-4511-access-settings-from-any-frontend.test.lua
index d27fec3..9049fab 100644
--- a/test/box/gh-4511-access-settings-from-any-frontend.test.lua
+++ b/test/box/gh-4511-access-settings-from-any-frontend.test.lua
@@ -19,23 +19,88 @@ s:insert({'a', 1})
 s:delete({'b'})
 s:replace({'sql_defer_foreign_keys', true})
 
--- Check get() and select(). They should return nothing for now.
-s:get({'a'})
-s:select()
-s:select({}, {iterator='EQ'})
-s:select({}, {iterator='ALL'})
-s:select({}, {iterator='GE'})
-s:select({}, {iterator='GT'})
-s:select({}, {iterator='REQ'})
-s:select({}, {iterator='LE'})
-s:select({}, {iterator='LT'})
-s:select({'a'}, {iterator='EQ'})
-s:select({'a'}, {iterator='ALL'})
-s:select({'a'}, {iterator='GE'})
-s:select({'a'}, {iterator='GT'})
-s:select({'a'}, {iterator='REQ'})
-s:select({'a'}, {iterator='LE'})
-s:select({'a'}, {iterator='LT'})
-
--- Currently there is nothing to update, but update() should work.
-s:update('some_option', {{'=', 'value', true}})
+--
+-- Check select() method of session_settings space. Should work
+-- the same way as an ordinary space with an index of the type
+-- "TREE".
+--
+t = box.schema.space.create('settings', {format = s:format()})
+_ = t:create_index('primary')
+for _,value in s:pairs() do t:insert(value) end
+
+test_run:cmd('setopt delimiter ";"')
+function check_sorting(ss, ts, key)
+    local iterators_list = {'ALL', 'REQ', 'EQ', 'GE', 'GT', 'LE', 'LT'}
+    for _, it in pairs(iterators_list) do
+        local view_space = ss:select({key}, {iterator = it})
+        local test_space = ts:select({key}, {iterator = it})
+        for key, value in pairs(view_space) do
+            if test_space[key].name ~= value.name then
+                return {
+                    err = 'bad sorting', type = it,
+                    exp = test_space[key].name, got = value.name
+                }
+            end
+        end
+    end
+end;
+test_run:cmd('setopt delimiter ""');
+
+check_sorting(s, t)
+check_sorting(s, t, 'abcde')
+check_sorting(s, t, 'sql_d')
+check_sorting(s, t, 'sql_v')
+check_sorting(s, t, 'sql_defer_foreign_keys')
+
+t:drop()
+
+-- Check get() method of session_settings space.
+s:get({'sql_defer_foreign_keys'})
+s:get({'sql_recursive_triggers'})
+s:get({'sql_reverse_unordered_selects'})
+s:get({'sql_default_engine'})
+s:get({'abcd'})
+
+-- Check pairs() method of session_settings space.
+t = {}
+for key, value in s:pairs() do table.insert(t, {key, value}) end
+#t == s:count()
+
+-- Check update() method of session_settings space.
+
+-- Correct updates.
+s:update('sql_defer_foreign_keys', {{'=', 'value', true}})
+s:update({'sql_defer_foreign_keys'}, {{'=', 2, false}})
+s:update('sql_default_engine', {{'=', 2, 'vinyl'}})
+s:update('sql_default_engine', {{':', 'value', 1, 5, 'memtx'}})
+s:update('a', {{'=', 2, 1}})
+
+-- Inorrect updates.
+s:update({{'sql_defer_foreign_keys'}}, {{'=', 'value', true}})
+
+s:update('sql_defer_foreign_keys', {'=', 'value', true})
+s:update('sql_defer_foreign_keys', {{'=', 'value', true}, {'=', 2, true}})
+s:update('sql_defer_foreign_keys', {{}})
+s:update('sql_defer_foreign_keys', {{'='}})
+s:update('sql_defer_foreign_keys', {{'=', 'value'}})
+s:update('sql_defer_foreign_keys', {{'=', 'value', true, 1}})
+
+s:update('sql_defer_foreign_keys', {{'+', 'value', 2}})
+s:update('sql_defer_foreign_keys', {{'-', 'value', 2}})
+s:update('sql_defer_foreign_keys', {{'&', 'value', 2}})
+s:update('sql_defer_foreign_keys', {{'|', 'value', 2}})
+s:update('sql_defer_foreign_keys', {{'^', 'value', 2}})
+s:update('sql_defer_foreign_keys', {{'!', 'value', 2}})
+s:update('sql_defer_foreign_keys', {{'#', 'value', 2}})
+s:update('sql_defer_foreign_keys', {{1, 'value', true}})
+s:update('sql_defer_foreign_keys', {{{1}, 'value', true}})
+
+s:update('sql_defer_foreign_keys', {{'=', {'value'}, true}})
+s:update('sql_defer_foreign_keys', {{'=', 1, 'new_key'}})
+s:update('sql_defer_foreign_keys', {{'=', 'name', 'new_key'}})
+s:update('sql_defer_foreign_keys', {{'=', 3, true}})
+s:update('sql_defer_foreign_keys', {{'=', 'some text', true}})
+
+s:update('sql_defer_foreign_keys', {{'=', 'value', 1}})
+s:update('sql_defer_foreign_keys', {{'=', 'value', {1}}})
+s:update('sql_defer_foreign_keys', {{'=', 'value', '1'}})
diff --git a/test/box/misc.result b/test/box/misc.result
index 6a8b697..94aa3ab 100644
--- a/test/box/misc.result
+++ b/test/box/misc.result
@@ -555,6 +555,7 @@ t;
   204: box.error.SQL_FUNC_WRONG_RET_COUNT
   205: box.error.FUNC_INVALID_RETURN_TYPE
   206: box.error.SQL_PARSER_GENERIC_WITH_POS
+  207: box.error.SESSION_SETTING_INVALID_VALUE
 ...
 test_run:cmd("setopt delimiter ''");
 ---
-- 
2.7.4

Re: [Tarantool-patches] [PATCH v5 0/3] Introduce _session_setting system space

[Vladislav Shpilevoy]

I've filed a couple of follow-up issues:
https://github.com/tarantool/tarantool/issues/4712
https://github.com/tarantool/tarantool/issues/4711

On 27/12/2019 15:05, imeevma@tarantool.org wrote:
> This patch-set creates _session_settings system space. This space
> is used to view and change session settings.
> 
> https://github.com/tarantool/tarantool/issues/4511
> https://github.com/tarantool/tarantool/tree/imeevma/gh-4511-new-engine
> 
> Mergen Imeev (3):
>   box: introduce 'virtual' engine
>   box: introduce _session_settings system space
>   box: add SQL settings to _session_settings
> 

[Tarantool-patches] [PATCH v5 0/3] Introduce _session_setting system space

[imeevma]

This patch-set creates _session_settings system space. This space
is used to view and change session settings.

https://github.com/tarantool/tarantool/issues/4511
https://github.com/tarantool/tarantool/tree/imeevma/gh-4511-new-engine

Mergen Imeev (3):
  box: introduce 'virtual' engine
  box: introduce _session_settings system space
  box: add SQL settings to _session_settings

 src/box/CMakeLists.txt                             |   2 +
 src/box/bootstrap.snap                             | Bin 5921 -> 5975 bytes
 src/box/box.cc                                     |   4 +
 src/box/errcode.h                                  |   1 +
 src/box/lua/space.cc                               |   2 +
 src/box/lua/upgrade.lua                            |  15 +
 src/box/schema_def.h                               |   8 +
 src/box/session_settings.c                         | 472 +++++++++++++++++++++
 src/box/session_settings.h                         |  70 +++
 src/box/sql.c                                      |   5 +
 src/box/sql/build.c                                | 222 ++++++++++
 src/box/virtual_engine.c                           | 135 ++++++
 src/box/virtual_engine.h                           |  53 +++
 test/app-tap/tarantoolctl.test.lua                 |   4 +-
 test/box-py/bootstrap.result                       |   3 +
 test/box/access_sysview.result                     |   6 +-
 test/box/alter.result                              |   5 +-
 ...h-4511-access-settings-from-any-frontend.result | 273 ++++++++++++
 ...4511-access-settings-from-any-frontend.test.lua | 106 +++++
 test/box/misc.result                               |   1 +
 test/wal_off/alter.result                          |   2 +-
 21 files changed, 1381 insertions(+), 8 deletions(-)
 create mode 100644 src/box/session_settings.c
 create mode 100644 src/box/session_settings.h
 create mode 100644 src/box/virtual_engine.c
 create mode 100644 src/box/virtual_engine.h
 create mode 100644 test/box/gh-4511-access-settings-from-any-frontend.result
 create mode 100644 test/box/gh-4511-access-settings-from-any-frontend.test.lua

-- 
2.7.4