[Tarantool-patches] [PATCH 0/4] box: session settings fixes

[Tarantool-patches] [PATCH 0/4] box: session settings fixes

[Chris Sosnin]

The first patch just merges all modules into one array, so the
binary search will work once for all settings.

The second patch is implementation of the binary search.

The last two patches add frontend for accessing session settings:
Lua table and SQL statement respectively.

branch: https://github.com/tarantool/tarantool/tree/ksosnin/gh-4712-search-settings
issue #1: https://github.com/tarantool/tarantool/issues/4711
issue #2: https://github.com/tarantool/tarantool/issues/4712

Chris Sosnin (4):
  box: replace session_settings modules with a single array
  box: add binary search for _session_settings space
  box: provide a user friendly frontend for accessing session settings
  sql: provide a user friendly frontend for accessing session settings

 src/box/lua/session.c                         |  92 ++++++++
 src/box/session.cc                            |   1 +
 src/box/session.h                             |   2 +
 src/box/session_settings.c                    | 214 +++++++++++-------
 src/box/session_settings.h                    |  53 +++--
 src/box/sql.c                                 |   5 -
 src/box/sql/build.c                           | 104 ++++-----
 src/box/sql/parse.y                           |   5 +
 src/box/sql/sqlInt.h                          |  11 +
 src/box/sql/vdbe.c                            |  50 ++++
 ...rontend.result => session_settings.result} | 149 ++++++++++--
 ...end.test.lua => session_settings.test.lua} |  61 ++++-
 12 files changed, 571 insertions(+), 176 deletions(-)
 rename test/box/{gh-4511-access-settings-from-any-frontend.result => session_settings.result} (71%)
 rename test/box/{gh-4511-access-settings-from-any-frontend.test.lua => session_settings.test.lua} (65%)

-- 
2.21.1 (Apple Git-122.3)

[Tarantool-patches] [PATCH 1/4] box: replace session_settings modules with a single array

[Chris Sosnin]

Currently we have an array of modules and each module has
its own array of session_settings. This patch merges these
into one array, as long as it turned out, that we cannot
represent every setting as a part of some module. This
change is also needed for implementing binary search for
_session_settings space.

Part of #4711, #4712
---
 src/box/session_settings.c | 121 ++++++++++++++-----------------------
 src/box/session_settings.h |  50 +++++++++------
 src/box/sql/build.c        |  79 +++++++-----------------
 3 files changed, 101 insertions(+), 149 deletions(-)

diff --git a/src/box/session_settings.c b/src/box/session_settings.c
index a969d3d10..93d1c8e22 100644
--- a/src/box/session_settings.c
+++ b/src/box/session_settings.c
@@ -38,8 +38,20 @@
 #include "xrow.h"
 #include "sql.h"
 
-struct session_setting_module
-	session_setting_modules[session_setting_type_MAX] = {};
+struct session_setting session_settings[SESSION_SETTING_COUNT] = {};
+
+/** Corresponding names of session settings. */
+const char *session_setting_strs[SESSION_SETTING_COUNT] = {
+	"sql_default_engine",
+	"sql_defer_foreign_keys",
+	"sql_full_column_names",
+	"sql_full_metadata",
+	"sql_parser_debug",
+	"sql_recursive_triggers",
+	"sql_reverse_unordered_selects",
+	"sql_select_debug",
+	"sql_vdbe_debug",
+};
 
 struct session_settings_index {
 	/** Base index. Must be the first member. */
@@ -61,12 +73,7 @@ struct session_settings_iterator {
 	 * 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. */
+	/** ID of the setting. */
 	int setting_id;
 	/** Decoded key. */
 	char *key;
@@ -86,46 +93,40 @@ session_settings_iterator_free(struct iterator *ptr)
 }
 
 static int
-session_settings_next_in_module(const struct session_setting_module *module,
-				int *sid, const char *key, bool is_eq,
-				bool is_including)
+session_settings_next(int *sid, const char *key, bool is_eq, bool is_including)
 {
 	int i = *sid;
-	int count = module->setting_count;
-	if (i >= count)
+	if (i >= SESSION_SETTING_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);
+	for (; i < SESSION_SETTING_COUNT; ++i) {
+		const char *name = session_setting_strs[i];
+		int cmp = strcmp(name, key);
 		if ((cmp == 0 && is_including) ||
 		    (cmp > 0 && !is_eq)) {
 			*sid = i;
 			return 0;
 		}
 	}
-	*sid = count;
+	*sid = SESSION_SETTING_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)
+session_settings_prev(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 (i >= SESSION_SETTING_COUNT)
+		i = SESSION_SETTING_COUNT - 1;
+	for (; i >= 0; --i) {
+		const char *name = session_setting_strs[i];
+		int cmp = strcmp(name, key);
 		if ((cmp == 0 && is_including) ||
 		    (cmp < 0 && !is_eq)) {
 			*sid = i;
@@ -141,27 +142,19 @@ 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;
+	int sid = it->setting_id;
 	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;
+	if (session_settings_next(&sid, key, is_eq, is_including) == 0)
+		is_found = true;
 	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);
+	session_settings[sid].get(sid, &mp_pair, &mp_pair_end);
 	*result = box_tuple_new(it->format, mp_pair, mp_pair_end);
 	return *result != NULL ? 0 : -1;
 }
@@ -171,27 +164,19 @@ 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;
+	int sid = it->setting_id;
 	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;
+	if (session_settings_prev(&sid, key, is_eq, is_including) == 0)
+		is_found = true;
 	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);
+	session_settings[sid].get(sid, &mp_pair, &mp_pair_end);
 	*result = box_tuple_new(it->format, mp_pair, mp_pair_end);
 	return *result != NULL ? 0 : -1;
 }
@@ -239,14 +224,10 @@ session_settings_index_create_iterator(struct index *base,
 	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;
+		it->setting_id = SESSION_SETTING_COUNT - 1;
 	}
 	return (struct iterator *)it;
 }
@@ -262,20 +243,14 @@ session_settings_index_get(struct index *base, const char *key,
 	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;
+	if (session_settings_next(&sid, key, true, true) != 0) {
+		*result = NULL;
+		return 0;
 	}
-	*result = NULL;
-	return 0;
-found:;
 	const char *mp_pair;
 	const char *mp_pair_end;
-	module->get(sid, &mp_pair, &mp_pair_end);
+	session_settings[sid].get(sid, &mp_pair, &mp_pair_end);
 	*result = box_tuple_new(index->format, mp_pair, mp_pair_end);
 	return *result != NULL ? 0 : -1;
 }
@@ -370,17 +345,11 @@ session_settings_space_execute_update(struct space *space, struct txn *txn,
 	}
 	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;
+	if (session_settings_next(&sid, key, true, true) != 0) {
+		*result = NULL;
+		return 0;
 	}
-	*result = NULL;
-	return 0;
-found:
-	module->get(sid, &old_data, &old_data_end);
+	session_settings[sid].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,
@@ -402,7 +371,7 @@ found:
 			goto finish;
 		}
 	}
-	if (module->set(sid, new_data) != 0)
+	if (session_settings[sid].set(sid, new_data) != 0)
 		goto finish;
 	rc = 0;
 finish:
diff --git a/src/box/session_settings.h b/src/box/session_settings.h
index 25490a7e3..de24e3c6f 100644
--- a/src/box/session_settings.h
+++ b/src/box/session_settings.h
@@ -30,29 +30,44 @@
  * SUCH DAMAGE.
  */
 
+#include "field_def.h"
+
 /**
- * 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.
+ * Identifiers of all session settings. The identifier of the
+ * option is equal to its place in the sorted list of session
+ * options.
  *
- * The types should be ordered in alphabetical order, because the
- * type list is used by setting iterators.
+ * 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 session_setting_type {
-	SESSION_SETTING_SQL,
-	session_setting_type_MAX,
+enum {
+	SESSION_SETTING_SQL_BEGIN,
+	SESSION_SETTING_SQL_DEFAULT_ENGINE = SESSION_SETTING_SQL_BEGIN,
+	SESSION_SETTING_SQL_DEFER_FOREIGN_KEYS,
+	SESSION_SETTING_SQL_FULL_COLUMN_NAMES,
+	SESSION_SETTING_SQL_FULL_METADATA,
+	SESSION_SETTING_SQL_PARSER_DEBUG,
+	SESSION_SETTING_SQL_RECURSIVE_TRIGGERS,
+	SESSION_SETTING_SQL_REVERSE_UNORDERED_SELECTS,
+	SESSION_SETTING_SQL_SELECT_DEBUG,
+	SESSION_SETTING_SQL_VDBE_DEBUG,
+	SESSION_SETTING_SQL_END,
+	/**
+	 * Follow the pattern for groups of settings:
+	 * SESSION_SETTING_<N>_BEGIN = SESSION_SETTING_<N-1>_END,
+	 * ...
+	 * SESSION_SETTING_<N>_END,
+	 */
+	SESSION_SETTING_COUNT = SESSION_SETTING_SQL_END,
 };
 
-struct session_setting_module {
+struct session_setting {
 	/**
-	 * An array of setting names. All of them should have the
-	 * same prefix.
+	 * Setting's value type. Used for error checking and
+	 * reporting only.
 	 */
-	const char **settings;
-	/** Count of settings. */
-	int setting_count;
+	enum field_type field_type;
 	/**
 	 * Get a MessagePack encoded pair [name, value] for a
 	 * setting having index @a id. Index is from the settings
@@ -67,4 +82,5 @@ struct session_setting_module {
 	int (*set)(int id, const char *mp_value);
 };
 
-extern struct session_setting_module session_setting_modules[];
+extern struct session_setting session_settings[SESSION_SETTING_COUNT];
+extern const char *session_setting_strs[SESSION_SETTING_COUNT];
diff --git a/src/box/sql/build.c b/src/box/sql/build.c
index bc50ecbfa..e5fde08cc 100644
--- a/src/box/sql/build.c
+++ b/src/box/sql/build.c
@@ -3310,40 +3310,6 @@ sql_fieldno_by_name(struct Parse *parse_context, struct Expr *field_name,
 	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,
-	SQL_SESSION_SETTING_PARSER_DEBUG,
-	SQL_SESSION_SETTING_RECURSIVE_TRIGGERS,
-	SQL_SESSION_SETTING_REVERSE_UNORDERED_SELECTS,
-	SQL_SESSION_SETTING_SELECT_DEBUG,
-	SQL_SESSION_SETTING_VDBE_DEBUG,
-	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",
-	"sql_parser_debug",
-	"sql_recursive_triggers",
-	"sql_reverse_unordered_selects",
-	"sql_select_debug",
-	"sql_vdbe_debug",
-};
-
 /**
  * A local structure that allows to establish a connection between
  * parameter and its field type and mask, if it has one.
@@ -3361,24 +3327,24 @@ struct sql_option_metadata
  * It is IMPORTANT that these options sorted by name.
  */
 static struct sql_option_metadata sql_session_opts[] = {
-	/** SQL_SESSION_SETTING_DEFAULT_ENGINE */
+	/** SESSION_SETTING_SQL_DEFAULT_ENGINE */
 	{FIELD_TYPE_STRING, 0},
-	/** SQL_SESSION_SETTING_DEFER_FOREIGN_KEYS */
+	/** SESSION_SETTING_SQL_DEFER_FOREIGN_KEYS */
 	{FIELD_TYPE_BOOLEAN, SQL_DeferFKs},
-	/** SQL_SESSION_SETTING_FULL_COLUMN_NAMES */
+	/** SESSION_SETTING_SQL_FULL_COLUMN_NAMES */
 	{FIELD_TYPE_BOOLEAN, SQL_FullColNames},
-	/** SQL_SESSION_SETTING_FULL_METADATA */
+	/** SESSION_SETTING_SQL_FULL_METADATA */
 	{FIELD_TYPE_BOOLEAN, SQL_FullMetadata},
-	/** SQL_SESSION_SETTING_PARSER_DEBUG */
+	/** SESSION_SETTING_SQL_PARSER_DEBUG */
 	{FIELD_TYPE_BOOLEAN, SQL_SqlTrace | PARSER_TRACE_FLAG},
-	/** SQL_SESSION_SETTING_RECURSIVE_TRIGGERS */
+	/** SESSION_SETTING_SQL_RECURSIVE_TRIGGERS */
 	{FIELD_TYPE_BOOLEAN, SQL_RecTriggers},
-	/** SQL_SESSION_SETTING_REVERSE_UNORDERED_SELECTS */
+	/** SESSION_SETTING_SQL_REVERSE_UNORDERED_SELECTS */
 	{FIELD_TYPE_BOOLEAN, SQL_ReverseOrder},
-	/** SQL_SESSION_SETTING_SELECT_DEBUG */
+	/** SESSION_SETTING_SQL_SELECT_DEBUG */
 	{FIELD_TYPE_BOOLEAN,
 	 SQL_SqlTrace | SQL_SelectTrace | SQL_WhereTrace},
-	/** SQL_SESSION_SETTING_VDBE_DEBUG */
+	/** SESSION_SETTING_SQL_VDBE_DEBUG */
 	{FIELD_TYPE_BOOLEAN,
 	 SQL_SqlTrace | SQL_VdbeListing | SQL_VdbeTrace},
 };
@@ -3386,12 +3352,12 @@ static struct sql_option_metadata sql_session_opts[] = {
 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);
+	assert(id >= SESSION_SETTING_SQL_BEGIN && id < SESSION_SETTING_SQL_END);
 	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];
+	const char *name = session_setting_strs[id];
 	size_t name_len = strlen(name);
 	size_t engine_len;
 	const char *engine;
@@ -3404,7 +3370,7 @@ sql_session_setting_get(int id, const char **mp_pair, const char **mp_pair_end)
 	if (is_bool) {
 		size += mp_sizeof_bool(true);
 	} else {
-		assert(id == SQL_SESSION_SETTING_DEFAULT_ENGINE);
+		assert(id == SESSION_SETTING_SQL_DEFAULT_ENGINE);
 		engine = sql_storage_engine_strs[session->sql_default_engine];
 		engine_len = strlen(engine);
 		size += mp_sizeof_str(engine_len);
@@ -3440,7 +3406,7 @@ sql_set_boolean_option(int id, bool value)
 		session->sql_flags |= option->mask;
 	else
 		session->sql_flags &= ~option->mask;
-	if (id == SQL_SESSION_SETTING_PARSER_DEBUG) {
+	if (id == SESSION_SETTING_SQL_PARSER_DEBUG) {
 		if (value)
 			sqlParserTrace(stdout, "parser: ");
 		else
@@ -3454,7 +3420,7 @@ 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);
+	assert(id == SESSION_SETTING_SQL_DEFAULT_ENGINE);
 	(void)id;
 	enum sql_storage_engine engine = STR2ENUM(sql_storage_engine, value);
 	if (engine == sql_storage_engine_MAX) {
@@ -3468,7 +3434,7 @@ sql_set_string_option(int id, const char *value)
 static int
 sql_session_setting_set(int id, const char *mp_value)
 {
-	assert(id >= 0 && id < sql_session_setting_MAX);
+	assert(id >= SESSION_SETTING_SQL_BEGIN && id < SESSION_SETTING_SQL_END);
 	enum mp_type mtype = mp_typeof(*mp_value);
 	enum field_type stype = sql_session_opts[id].field_type;
 	uint32_t len;
@@ -3488,17 +3454,18 @@ sql_session_setting_set(int id, const char *mp_value)
 		unreachable();
 	}
 	diag_set(ClientError, ER_SESSION_SETTING_INVALID_VALUE,
-		 sql_session_setting_strs[id], field_type_strs[stype]);
+		 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;
+	for (int id = SESSION_SETTING_SQL_BEGIN; id < SESSION_SETTING_SQL_END;
+	     ++id) {
+		struct session_setting *setting = &session_settings[id];
+		setting->field_type = sql_session_opts[id].field_type;
+		setting->get = sql_session_setting_get;
+		setting->set = sql_session_setting_set;
+	}
 }
-- 
2.21.1 (Apple Git-122.3)

[Tarantool-patches] [PATCH 2/4] box: add binary search for _session_settings space

[Chris Sosnin]

As it is mentioned in implementation, it is important
that _session_settings options are sorted by name, so
there is no need in linear lookup and we can replace it
with binary search.

Closes #4712
---
 src/box/session_settings.c                    | 97 +++++++++++++++++--
 ...1-access-settings-from-any-frontend.result | 37 ++++---
 ...access-settings-from-any-frontend.test.lua | 28 ++++--
 3 files changed, 133 insertions(+), 29 deletions(-)

diff --git a/src/box/session_settings.c b/src/box/session_settings.c
index 93d1c8e22..874fc304a 100644
--- a/src/box/session_settings.c
+++ b/src/box/session_settings.c
@@ -81,6 +81,8 @@ struct session_settings_iterator {
 	bool is_eq;
 	/** True if the iterator should include equal keys. */
 	bool is_including;
+	/** True if the iterator is pointing to an existing setting */
+	bool is_set;
 };
 
 static void
@@ -92,6 +94,72 @@ session_settings_iterator_free(struct iterator *ptr)
 	free(it);
 }
 
+static int
+session_settings_set_forward(int *sid, const char *key, bool is_eq,
+			     bool is_including)
+{
+	int low = 0, high = SESSION_SETTING_COUNT - 1;
+	if (key == NULL)
+		return 0;
+	while (low <= high) {
+		int index = (high + low) / 2;
+		const char *name = session_setting_strs[index];
+		int cmp = strcmp(name, key);
+		if (cmp == 0) {
+			if (is_including) {
+				*sid = index;
+				return 0;
+			}
+			*sid = ++index;
+			return index < SESSION_SETTING_COUNT ? 0 : -1;
+		}
+		if (cmp < 0)
+			low = index + 1;
+		else
+			high = index - 1;
+	}
+	if (is_eq) {
+		*sid = SESSION_SETTING_COUNT;
+		return -1;
+	}
+	assert(low > high);
+	*sid = low;
+	return low < SESSION_SETTING_COUNT ? 0 : -1;
+}
+
+static int
+session_settings_set_reverse(int *sid, const char *key, bool is_eq,
+			     bool is_including)
+{
+	int low = 0, high = SESSION_SETTING_COUNT - 1;
+	if (key == NULL)
+		return 0;
+	while (low <= high) {
+		int index = (high + low) / 2;
+		const char *name = session_setting_strs[index];
+		int cmp = strcmp(name, key);
+		if (cmp == 0) {
+			if (is_including) {
+				*sid = index;
+				return 0;
+			}
+			*sid = --index;
+			return index >= 0 ? 0 : -1;
+		}
+		if (cmp < 0)
+			low = index + 1;
+		else
+			high = index - 1;
+	}
+	if (is_eq) {
+		*sid = SESSION_SETTING_COUNT;
+		return -1;
+	}
+	assert(low > high);
+	*sid = high;
+	return high >= 0 ? 0 : -1;
+}
+
 static int
 session_settings_next(int *sid, const char *key, bool is_eq, bool is_including)
 {
@@ -145,9 +213,15 @@ session_settings_iterator_next(struct iterator *iterator, struct tuple **result)
 	int sid = it->setting_id;
 	const char *key = it->key;
 	bool is_including = it->is_including, is_eq = it->is_eq;
-	bool is_found = false;
-	if (session_settings_next(&sid, key, is_eq, is_including) == 0)
-		is_found = true;
+	bool is_found;
+	if (!it->is_set) {
+		it->is_set = true;
+		is_found = session_settings_set_forward(&sid, key, is_eq,
+							is_including) == 0;
+	} else {
+		is_found = session_settings_next(&sid, key, is_eq,
+						 is_including) == 0;
+	}
 	it->setting_id = sid + 1;
 	if (!is_found) {
 		*result = NULL;
@@ -167,9 +241,15 @@ session_settings_iterator_prev(struct iterator *iterator, struct tuple **result)
 	int sid = it->setting_id;
 	const char *key = it->key;
 	bool is_including = it->is_including, is_eq = it->is_eq;
-	bool is_found = false;
-	if (session_settings_prev(&sid, key, is_eq, is_including) == 0)
-		is_found = true;
+	bool is_found;
+	if (!it->is_set) {
+		it->is_set = true;
+		is_found = session_settings_set_reverse(&sid, key, is_eq,
+							is_including) == 0;
+	} else {
+		is_found = session_settings_prev(&sid, key, is_eq,
+						 is_including) == 0;
+	}
 	it->setting_id = sid - 1;
 	if (!is_found) {
 		*result = NULL;
@@ -221,6 +301,7 @@ session_settings_index_create_iterator(struct index *base,
 	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->is_set = false;
 	it->format = index->format;
 	if (!iterator_type_is_reverse(type)) {
 		it->base.next = session_settings_iterator_next;
@@ -244,7 +325,7 @@ session_settings_index_get(struct index *base, const char *key,
 	key = mp_decode_str(&key, &len);
 	key = tt_cstr(key, len);
 	int sid = 0;
-	if (session_settings_next(&sid, key, true, true) != 0) {
+	if (session_settings_set_forward(&sid, key, true, true) != 0) {
 		*result = NULL;
 		return 0;
 	}
@@ -345,7 +426,7 @@ session_settings_space_execute_update(struct space *space, struct txn *txn,
 	}
 	key = mp_decode_str(&key, &key_len);
 	key = tt_cstr(key, key_len);
-	if (session_settings_next(&sid, key, true, true) != 0) {
+	if (session_settings_set_forward(&sid, key, true, true) != 0) {
 		*result = NULL;
 		return 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 ed340d053..bae77192e 100644
--- a/test/box/gh-4511-access-settings-from-any-frontend.result
+++ b/test/box/gh-4511-access-settings-from-any-frontend.result
@@ -82,6 +82,12 @@ function check_sorting(ss, ts, key)
     for _, it in pairs(iterators_list) do
         local view_space = ss:select({key}, {iterator = it})
         local test_space = ts:select({key}, {iterator = it})
+        if #view_space ~= #test_space then
+            return {
+                err = 'bad sorting', type = it, exp = test_space,
+                got = view_space
+            }
+        end
         for key, value in pairs(view_space) do
             if test_space[key].name ~= value.name then
                 return {
@@ -111,32 +117,37 @@ check_sorting(s, t, 'sql_d')
 check_sorting(s, t, 'sql_v')
  | ---
  | ...
-check_sorting(s, t, 'sql_defer_foreign_keys')
+check_sorting(s, t, 'z')
  | ---
  | ...
-
-t:drop()
+check_sorting(s, t, 'sql_parser_debuf')
+ | ---
+ | ...
+check_sorting(s, t, 'sql_parser_debuh')
  | ---
  | ...
 
--- Check get() method of session_settings space.
-s:get({'sql_defer_foreign_keys'})
+name = nil
  | ---
- | - ['sql_defer_foreign_keys', false]
  | ...
-s:get({'sql_recursive_triggers'})
+err = nil
  | ---
- | - ['sql_recursive_triggers', true]
  | ...
-s:get({'sql_reverse_unordered_selects'})
+for _, tuple in t:pairs() do                    \
+    name = tuple.name                           \
+    err = check_sorting(s, t, name)             \
+    if err then                                 \
+        break                                   \
+    end                                         \
+end
  | ---
- | - ['sql_reverse_unordered_selects', false]
  | ...
-s:get({'sql_default_engine'})
+err and {err, name}
  | ---
- | - ['sql_default_engine', 'memtx']
+ | - null
  | ...
-s:get({'abcd'})
+
+t:drop()
  | ---
  | ...
 
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 366874998..b243be15e 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
@@ -36,6 +36,12 @@ function check_sorting(ss, ts, key)
     for _, it in pairs(iterators_list) do
         local view_space = ss:select({key}, {iterator = it})
         local test_space = ts:select({key}, {iterator = it})
+        if #view_space ~= #test_space then
+            return {
+                err = 'bad sorting', type = it, exp = test_space,
+                got = view_space
+            }
+        end
         for key, value in pairs(view_space) do
             if test_space[key].name ~= value.name then
                 return {
@@ -52,17 +58,23 @@ 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')
+check_sorting(s, t, 'z')
+check_sorting(s, t, 'sql_parser_debuf')
+check_sorting(s, t, 'sql_parser_debuh')
+
+name = nil
+err = nil
+for _, tuple in t:pairs() do                    \
+    name = tuple.name                           \
+    err = check_sorting(s, t, name)             \
+    if err then                                 \
+        break                                   \
+    end                                         \
+end
+err and {err, name}
 
 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
-- 
2.21.1 (Apple Git-122.3)

[Tarantool-patches] [PATCH 3/4] box: provide a user friendly frontend for accessing session settings

[Chris Sosnin]

- space_object:update() is hard to use for configuring session settings,
so we provide box.session.setting table, which can be used in a much more
native way.

- Prior to this patch sql settings were not accessible before box.cfg()
call, even though these flags can be set right after session creation.

Part of #4711
---
 src/box/lua/session.c                         | 92 +++++++++++++++++++
 src/box/session.cc                            |  1 +
 src/box/session.h                             |  2 +
 src/box/sql.c                                 |  5 -
 ...rontend.result => session_settings.result} | 63 +++++++++++++
 ...end.test.lua => session_settings.test.lua} | 20 ++++
 6 files changed, 178 insertions(+), 5 deletions(-)
 rename test/box/{gh-4511-access-settings-from-any-frontend.result => session_settings.result} (86%)
 rename test/box/{gh-4511-access-settings-from-any-frontend.test.lua => session_settings.test.lua} (85%)

diff --git a/src/box/lua/session.c b/src/box/lua/session.c
index c6a600f6f..c0b4d6184 100644
--- a/src/box/lua/session.c
+++ b/src/box/lua/session.c
@@ -42,6 +42,8 @@
 #include "box/user.h"
 #include "box/schema.h"
 #include "box/port.h"
+#include "box/session_settings.h"
+#include "tt_static.h"
 
 static const char *sessionlib_name = "box.session";
 
@@ -411,6 +413,95 @@ lbox_session_on_access_denied(struct lua_State *L)
 				  lbox_push_on_access_denied_event, NULL);
 }
 
+static int
+lbox_session_setting_get(struct lua_State *L)
+{
+	lua_getfield(L, -1, "_id");
+	int sid = lua_tointeger(L, -1);
+	const char *mp_pair, *mp_pair_end;
+	session_settings[sid].get(sid, &mp_pair, &mp_pair_end);
+	uint32_t len;
+	mp_decode_array(&mp_pair);
+	mp_decode_str(&mp_pair, &len);
+	enum field_type field_type = session_settings[sid].field_type;
+	if (field_type == FIELD_TYPE_BOOLEAN) {
+		bool value = mp_decode_bool(&mp_pair);
+		lua_pushboolean(L, value);
+	} else {
+		const char *str = mp_decode_str(&mp_pair, &len);
+		lua_pushlstring(L, str, len);
+	}
+	return 1;
+}
+
+static int
+lbox_session_setting_set(struct lua_State *L)
+{
+	if (lua_gettop(L) != 2)
+		return luaL_error(L, "Usage: box.session.settings:set(value)");
+	int arg_type = lua_type(L, -1);
+	lua_getfield(L, -2, "_id");
+	int sid = lua_tointeger(L, -1);
+	struct session_setting *setting = &session_settings[sid];
+	lua_pop(L, 1);
+	switch (arg_type) {
+	case LUA_TBOOLEAN: {
+		bool value = lua_toboolean(L, -1);
+		size_t size = mp_sizeof_bool(value);
+		char *mp_value = (char *) static_alloc(size);
+		mp_encode_bool(mp_value, value);
+		if (setting->set(sid, mp_value) != 0)
+			return luaT_push_nil_and_error(L);
+		break;
+	}
+	case LUA_TSTRING: {
+		const char *str = lua_tostring(L, -1);
+		size_t len = strlen(str);
+		uint32_t size = mp_sizeof_str(len);
+		char *mp_value = (char *) static_alloc(size);
+		if (mp_value == NULL) {
+			diag_set(OutOfMemory, size, "static_alloc",
+				 "mp_value");
+			return luaT_error(L);
+		}
+		mp_encode_str(mp_value, str, len);
+		if (setting->set(sid, mp_value) != 0)
+			return luaT_push_nil_and_error(L);
+		break;
+	}
+	default:
+		diag_set(ClientError, ER_SESSION_SETTING_INVALID_VALUE,
+			 session_setting_strs[sid],
+			 field_type_strs[setting->field_type]);
+		return luaT_push_nil_and_error(L);
+	}
+	return 0;
+}
+
+static void
+lbox_session_settings_init(struct lua_State *L)
+{
+	lua_createtable(L, 0, 2);
+	lua_pushcfunction(L, lbox_session_setting_get);
+	lua_setfield(L, -2, "__serialize");
+	lua_createtable(L, 0, 1);
+	lua_pushcfunction(L, lbox_session_setting_set);
+	lua_setfield(L, -2, "set");
+	lua_setfield(L, -2, "__index");
+
+	lua_newtable(L);
+	for (int id = 0; id < SESSION_SETTING_COUNT; ++id) {
+		lua_newtable(L);
+		lua_pushinteger(L, id);
+		lua_setfield(L, -2, "_id");
+		lua_pushvalue(L, -3);
+		lua_setmetatable(L, -2);
+		lua_setfield(L, -2, session_setting_strs[id]);
+	}
+	lua_setfield(L, -3, "settings");
+	lua_pop(L, 1);
+}
+
 void
 session_storage_cleanup(int sid)
 {
@@ -478,5 +569,6 @@ box_lua_session_init(struct lua_State *L)
 		{NULL, NULL}
 	};
 	luaL_register_module(L, sessionlib_name, sessionlib);
+	lbox_session_settings_init(L);
 	lua_pop(L, 1);
 }
diff --git a/src/box/session.cc b/src/box/session.cc
index 881318252..b557eed62 100644
--- a/src/box/session.cc
+++ b/src/box/session.cc
@@ -283,6 +283,7 @@ session_init()
 		panic("out of memory");
 	mempool_create(&session_pool, &cord()->slabc, sizeof(struct session));
 	credentials_create(&admin_credentials, admin_user);
+	sql_session_settings_init();
 }
 
 void
diff --git a/src/box/session.h b/src/box/session.h
index 6dfc7cba5..1c47b8986 100644
--- a/src/box/session.h
+++ b/src/box/session.h
@@ -41,6 +41,8 @@
 extern "C" {
 #endif /* defined(__cplusplus) */
 
+extern void sql_session_settings_init();
+
 struct port;
 struct session_vtab;
 
diff --git a/src/box/sql.c b/src/box/sql.c
index 1256df856..ba98ce5df 100644
--- a/src/box/sql.c
+++ b/src/box/sql.c
@@ -64,14 +64,9 @@ static const uint32_t default_sql_flags = SQL_EnableTrigger
 					  | 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/test/box/gh-4511-access-settings-from-any-frontend.result b/test/box/session_settings.result
similarity index 86%
rename from test/box/gh-4511-access-settings-from-any-frontend.result
rename to test/box/session_settings.result
index bae77192e..6d7074e8c 100644
--- a/test/box/gh-4511-access-settings-from-any-frontend.result
+++ b/test/box/session_settings.result
@@ -298,3 +298,66 @@ s:update('sql_defer_foreign_keys', {{'=', 'value', '1'}})
  | ---
  | - error: Session setting sql_defer_foreign_keys expected a value of type boolean
  | ...
+
+-- gh-4711: Provide a user-friendly frontend for accessing session settings.
+settings = box.session.settings
+ | ---
+ | ...
+assert(settings ~= nil)
+ | ---
+ | - true
+ | ...
+
+s:update('sql_default_engine', {{'=', 2, 'vinyl'}})
+ | ---
+ | - ['sql_default_engine', 'vinyl']
+ | ...
+settings.sql_default_engine
+ | ---
+ | - vinyl
+ | ...
+settings.sql_default_engine:set('memtx')
+ | ---
+ | ...
+s:get('sql_default_engine').value
+ | ---
+ | - memtx
+ | ...
+settings.sql_defer_foreign_keys:set(true)
+ | ---
+ | ...
+s:get('sql_defer_foreign_keys').value
+ | ---
+ | - true
+ | ...
+s:update('sql_defer_foreign_keys', {{'=', 2, false}})
+ | ---
+ | - ['sql_defer_foreign_keys', false]
+ | ...
+settings.sql_defer_foreign_keys
+ | ---
+ | - false
+ | ...
+
+settings.sql_default_engine:set(true)
+ | ---
+ | - null
+ | - Session setting sql_default_engine expected a value of type string
+ | ...
+settings.sql_defer_foreign_keys:set(false, 1, 2, 3)
+ | ---
+ | - error: 'Usage: box.session.settings:set(value)'
+ | ...
+settings.sql_parser_debug:set('string')
+ | ---
+ | - null
+ | - Session setting sql_parser_debug expected a value of type boolean
+ | ...
+
+str = string.rep('a', 20 * 1024)
+ | ---
+ | ...
+box.session.settings.sql_default_engine:set(str)
+ | ---
+ | - error: Failed to allocate 20483 bytes in static_alloc for mp_value
+ | ...
diff --git a/test/box/gh-4511-access-settings-from-any-frontend.test.lua b/test/box/session_settings.test.lua
similarity index 85%
rename from test/box/gh-4511-access-settings-from-any-frontend.test.lua
rename to test/box/session_settings.test.lua
index b243be15e..23799874a 100644
--- a/test/box/gh-4511-access-settings-from-any-frontend.test.lua
+++ b/test/box/session_settings.test.lua
@@ -118,3 +118,23 @@ 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'}})
+
+-- gh-4711: Provide a user-friendly frontend for accessing session settings.
+settings = box.session.settings
+assert(settings ~= nil)
+
+s:update('sql_default_engine', {{'=', 2, 'vinyl'}})
+settings.sql_default_engine
+settings.sql_default_engine:set('memtx')
+s:get('sql_default_engine').value
+settings.sql_defer_foreign_keys:set(true)
+s:get('sql_defer_foreign_keys').value
+s:update('sql_defer_foreign_keys', {{'=', 2, false}})
+settings.sql_defer_foreign_keys
+
+settings.sql_default_engine:set(true)
+settings.sql_defer_foreign_keys:set(false, 1, 2, 3)
+settings.sql_parser_debug:set('string')
+
+str = string.rep('a', 20 * 1024)
+box.session.settings.sql_default_engine:set(str)
-- 
2.21.1 (Apple Git-122.3)

[Tarantool-patches] [PATCH 4/4] sql: provide a user friendly frontend for accessing session settings

[Chris Sosnin]

Currently if a user wants to change session setting with sql, he has
to execute non-obvious query, thus, we introduce a more native way to
do this.

Closes #4711

@TarantoolBot document
Title: API for accessing _session_settings space.
There are two ways of updating values of session settings:
via Lua and SQL.

Lua:
box.session.settings is a table, which is always accessible
to user. The syntax is the following:
`box.session.settings.<setting_name>:set(<new_value>)`.

Example of usage:
```
tarantool> box.session.settings.sql_default_engine
---
- memtx
...

tarantool> box.session.settings.sql_default_engine:set('vinyl')
---
...

```

The table itself represents the (unordered) result of select
from _session_settings space. Every setting is implemented as
a table, so there is no way to retrieve an actual value and use
it until :get() method is introduced.

SQL:
Instead of typing long UPDATE query one can use the SET statement:
`box.execute([[SET "<setting_name>" = <new_value>]])`.
Note, that this query is case sensitive so the name must be quoted.

Example:
```
tarantool> box.execute([[set "sql_default_engine" = 'memtx']])
---
- row_count: 1
...

tarantool> box.execute([[set "sql_defer_foreign_keys" = true]])
---
- row_count: 1
...

```
---
 src/box/session_settings.c         | 16 ++++++++--
 src/box/session_settings.h         |  3 ++
 src/box/sql/build.c                | 25 +++++++++++++++
 src/box/sql/parse.y                |  5 +++
 src/box/sql/sqlInt.h               | 11 +++++++
 src/box/sql/vdbe.c                 | 50 ++++++++++++++++++++++++++++++
 test/box/session_settings.result   | 49 +++++++++++++++++++++++++++++
 test/box/session_settings.test.lua | 13 ++++++++
 8 files changed, 169 insertions(+), 3 deletions(-)

diff --git a/src/box/session_settings.c b/src/box/session_settings.c
index 874fc304a..3d06a191a 100644
--- a/src/box/session_settings.c
+++ b/src/box/session_settings.c
@@ -324,8 +324,8 @@ session_settings_index_get(struct index *base, const char *key,
 	uint32_t len;
 	key = mp_decode_str(&key, &len);
 	key = tt_cstr(key, len);
-	int sid = 0;
-	if (session_settings_set_forward(&sid, key, true, true) != 0) {
+	int sid = session_setting_find(key);
+	if (sid < 0) {
 		*result = NULL;
 		return 0;
 	}
@@ -426,7 +426,8 @@ session_settings_space_execute_update(struct space *space, struct txn *txn,
 	}
 	key = mp_decode_str(&key, &key_len);
 	key = tt_cstr(key, key_len);
-	if (session_settings_set_forward(&sid, key, true, true) != 0) {
+	sid = session_setting_find(key);
+	if (sid < 0) {
 		*result = NULL;
 		return 0;
 	}
@@ -520,3 +521,12 @@ const struct space_vtab session_settings_space_vtab = {
 	/* .prepare_alter = */ generic_space_prepare_alter,
 	/* .invalidate = */ generic_space_invalidate,
 };
+
+int
+session_setting_find(const char *name) {
+	int sid;
+	if (session_settings_set_forward(&sid, name, true, true) == 0)
+		return sid;
+	else
+		return -1;
+}
diff --git a/src/box/session_settings.h b/src/box/session_settings.h
index de24e3c6f..e2adc5289 100644
--- a/src/box/session_settings.h
+++ b/src/box/session_settings.h
@@ -84,3 +84,6 @@ struct session_setting {
 
 extern struct session_setting session_settings[SESSION_SETTING_COUNT];
 extern const char *session_setting_strs[SESSION_SETTING_COUNT];
+
+int
+session_setting_find(const char *name);
diff --git a/src/box/sql/build.c b/src/box/sql/build.c
index e5fde08cc..9cbe25443 100644
--- a/src/box/sql/build.c
+++ b/src/box/sql/build.c
@@ -3469,3 +3469,28 @@ sql_session_settings_init()
 		setting->set = sql_session_setting_set;
 	}
 }
+
+void
+sql_setting_set(struct Parse *parse_context, struct Token *name,
+		struct Expr *expr)
+{
+	struct Vdbe *vdbe = sqlGetVdbe(parse_context);
+	if (vdbe == NULL)
+		goto abort;
+	sqlVdbeCountChanges(vdbe);
+	char *key = sql_name_from_token(parse_context->db, name);
+	if (key == NULL)
+		goto abort;
+	int index = session_setting_find(key);
+	if (index >= 0) {
+		int target = ++parse_context->nMem;
+		sqlExprCode(parse_context, expr, target);
+		sqlVdbeAddOp2(vdbe, OP_Set, index, target);
+		return;
+	}
+	diag_set(ClientError, ER_SQL_PARSER_GENERIC,
+		 tt_sprintf("Session setting %s doesn't exist", key));
+abort:
+	parse_context->is_aborted = true;
+	return;
+}
diff --git a/src/box/sql/parse.y b/src/box/sql/parse.y
index cfe1c0012..a01c37e19 100644
--- a/src/box/sql/parse.y
+++ b/src/box/sql/parse.y
@@ -1541,6 +1541,11 @@ cmd ::= DROP INDEX ifexists(E) nm(X) ON fullname(Y).   {
   sql_drop_index(pParse);
 }
 
+///////////////////////////// The SET command ////////////////////////////////
+cmd ::= SET nm(X) EQ expr(Y).  {
+    sql_setting_set(pParse,&X,Y.pExpr);
+}
+
 ///////////////////////////// The PRAGMA command /////////////////////////////
 //
 cmd ::= PRAGMA nm(X).                        {
diff --git a/src/box/sql/sqlInt.h b/src/box/sql/sqlInt.h
index d1fcf4761..3ffae5970 100644
--- a/src/box/sql/sqlInt.h
+++ b/src/box/sql/sqlInt.h
@@ -4510,4 +4510,15 @@ int
 sql_fieldno_by_name(struct Parse *parse_context, struct Expr *field_name,
 		    uint32_t *fieldno);
 
+/**
+ * Create VDBE instructions to set the new value of the session setting.
+ *
+ * @param parse_context Parsing context.
+ * @param name Name of the session setting.
+ * @param value New value of the session setting.
+ */
+void
+sql_setting_set(struct Parse *parse_context, struct Token *name,
+		struct Expr *value);
+
 #endif				/* sqlINT_H */
diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
index 620d74e66..c81486fa6 100644
--- a/src/box/sql/vdbe.c
+++ b/src/box/sql/vdbe.c
@@ -55,6 +55,7 @@
 #include "box/schema.h"
 #include "box/space.h"
 #include "box/sequence.h"
+#include "box/session_settings.h"
 
 /*
  * Invoke this macro on memory cells just prior to changing the
@@ -5248,6 +5249,55 @@ case OP_IncMaxid: {
 	break;
 }
 
+/* Opcode: Set P1 P2 * * *
+ *
+ * Set the new value of the session setting. P1 is the id of the
+ * setting in the session_settings array, P2 is the register
+ * holding a value.
+ */
+case OP_Set: {
+	int sid = pOp->p1;
+	pIn1 = &aMem[pOp->p2];
+	assert(sid >= 0 && sid < SESSION_SETTING_COUNT);
+	struct session_setting *setting = &session_settings[sid];
+	switch (setting->field_type) {
+	case FIELD_TYPE_BOOLEAN: {
+		if ((pIn1->flags & MEM_Bool) == 0)
+			goto invalid_type;
+		bool value = pIn1->u.b;
+		size_t size = mp_sizeof_bool(value);
+		char *mp_value = (char *) static_alloc(size);
+		mp_encode_bool(mp_value, value);
+		if (setting->set(sid, mp_value) != 0)
+			goto abort_due_to_error;
+		break;
+	}
+	case FIELD_TYPE_STRING: {
+		if ((pIn1->flags & MEM_Str) == 0)
+			goto invalid_type;
+		const char *str = pIn1->z;
+		uint32_t size = mp_sizeof_str(pIn1->n);
+		char *mp_value = (char *) static_alloc(size);
+		if (mp_value == NULL) {
+			diag_set(OutOfMemory, size, "static_alloc", "mp_value");
+			goto abort_due_to_error;
+		}
+		mp_encode_str(mp_value, str, pIn1->n);
+		if (setting->set(sid, mp_value) != 0)
+			goto abort_due_to_error;
+		break;
+	}
+	default:
+	invalid_type:
+		diag_set(ClientError, ER_SESSION_SETTING_INVALID_VALUE,
+			 session_setting_strs[sid],
+			 field_type_strs[setting->field_type]);
+		goto abort_due_to_error;
+	}
+	p->nChange++;
+	break;
+}
+
 /* Opcode: Noop * * * * *
  *
  * Do nothing.  This instruction is often useful as a jump
diff --git a/test/box/session_settings.result b/test/box/session_settings.result
index 6d7074e8c..7c9802af6 100644
--- a/test/box/session_settings.result
+++ b/test/box/session_settings.result
@@ -339,6 +339,39 @@ settings.sql_defer_foreign_keys
  | - false
  | ...
 
+box.execute([[set "sql_default_engine" = 'vinyl']])
+ | ---
+ | - row_count: 1
+ | ...
+s:get('sql_default_engine').value
+ | ---
+ | - vinyl
+ | ...
+box.execute([[set "sql_default_engine" = 'memtx']])
+ | ---
+ | - row_count: 1
+ | ...
+s:get('sql_default_engine').value
+ | ---
+ | - memtx
+ | ...
+box.execute([[set "sql_defer_foreign_keys" = true]])
+ | ---
+ | - row_count: 1
+ | ...
+s:get('sql_defer_foreign_keys').value
+ | ---
+ | - true
+ | ...
+box.execute([[set "sql_defer_foreign_keys" = ?]], {false})
+ | ---
+ | - row_count: 1
+ | ...
+s:get('sql_defer_foreign_keys').value
+ | ---
+ | - false
+ | ...
+
 settings.sql_default_engine:set(true)
  | ---
  | - null
@@ -361,3 +394,19 @@ box.session.settings.sql_default_engine:set(str)
  | ---
  | - error: Failed to allocate 20483 bytes in static_alloc for mp_value
  | ...
+
+box.execute([[set "sql_def_engine" = true]])
+ | ---
+ | - null
+ | - Session setting sql_def_engine doesn't exist
+ | ...
+box.execute([[set "sql_default_engine" = true]])
+ | ---
+ | - null
+ | - Session setting sql_default_engine expected a value of type string
+ | ...
+box.execute([[set "sql_defer_foreign_keys" = 'true']])
+ | ---
+ | - null
+ | - Session setting sql_defer_foreign_keys expected a value of type boolean
+ | ...
diff --git a/test/box/session_settings.test.lua b/test/box/session_settings.test.lua
index 23799874a..f2d7e03f5 100644
--- a/test/box/session_settings.test.lua
+++ b/test/box/session_settings.test.lua
@@ -132,9 +132,22 @@ s:get('sql_defer_foreign_keys').value
 s:update('sql_defer_foreign_keys', {{'=', 2, false}})
 settings.sql_defer_foreign_keys
 
+box.execute([[set "sql_default_engine" = 'vinyl']])
+s:get('sql_default_engine').value
+box.execute([[set "sql_default_engine" = 'memtx']])
+s:get('sql_default_engine').value
+box.execute([[set "sql_defer_foreign_keys" = true]])
+s:get('sql_defer_foreign_keys').value
+box.execute([[set "sql_defer_foreign_keys" = ?]], {false})
+s:get('sql_defer_foreign_keys').value
+
 settings.sql_default_engine:set(true)
 settings.sql_defer_foreign_keys:set(false, 1, 2, 3)
 settings.sql_parser_debug:set('string')
 
 str = string.rep('a', 20 * 1024)
 box.session.settings.sql_default_engine:set(str)
+
+box.execute([[set "sql_def_engine" = true]])
+box.execute([[set "sql_default_engine" = true]])
+box.execute([[set "sql_defer_foreign_keys" = 'true']])
-- 
2.21.1 (Apple Git-122.3)

Re: [Tarantool-patches] [PATCH 2/4] box: add binary search for _session_settings space

[Nikita Pettik]

On 17 Feb 15:12, Chris Sosnin wrote:
> As it is mentioned in implementation, it is important
> that _session_settings options are sorted by name, so
> there is no need in linear lookup and we can replace it
> with binary search.

Is there any sufficient performance benefit except for code complication?:)
I really doubt that this part should be optimized for such rare in
terms of usage place. What is more, there's only dozen entries, so
binary search doesn't really make any sence. Idk why Kirill assigned 2.4.1
milestone, IMHO there are way far more important things to elaborate on.
 
> Closes #4712
> ---
>  src/box/session_settings.c                    | 97 +++++++++++++++++--
>  ...1-access-settings-from-any-frontend.result | 37 ++++---
>  ...access-settings-from-any-frontend.test.lua | 28 ++++--
>  3 files changed, 133 insertions(+), 29 deletions(-)
> 
> diff --git a/src/box/session_settings.c b/src/box/session_settings.c
> index 93d1c8e22..874fc304a 100644
> --- a/src/box/session_settings.c
> +++ b/src/box/session_settings.c
> @@ -81,6 +81,8 @@ struct session_settings_iterator {
>  	bool is_eq;
>  	/** True if the iterator should include equal keys. */
>  	bool is_including;
> +	/** True if the iterator is pointing to an existing setting */
> +	bool is_set;
>  };
>  
>  static void
> @@ -92,6 +94,72 @@ session_settings_iterator_free(struct iterator *ptr)
>  	free(it);
>  }
>  
> +static int
> +session_settings_set_forward(int *sid, const char *key, bool is_eq,
> +			     bool is_including)
> +{
> +	int low = 0, high = SESSION_SETTING_COUNT - 1;
> +	if (key == NULL)
> +		return 0;
> +	while (low <= high) {
> +		int index = (high + low) / 2;
> +		const char *name = session_setting_strs[index];
> +		int cmp = strcmp(name, key);
> +		if (cmp == 0) {
> +			if (is_including) {
> +				*sid = index;
> +				return 0;
> +			}
> +			*sid = ++index;
> +			return index < SESSION_SETTING_COUNT ? 0 : -1;
> +		}
> +		if (cmp < 0)
> +			low = index + 1;
> +		else
> +			high = index - 1;
> +	}
> +	if (is_eq) {
> +		*sid = SESSION_SETTING_COUNT;
> +		return -1;
> +	}
> +	assert(low > high);
> +	*sid = low;
> +	return low < SESSION_SETTING_COUNT ? 0 : -1;
> +}
> +
> +static int
> +session_settings_set_reverse(int *sid, const char *key, bool is_eq,
> +			     bool is_including)
> +{
> +	int low = 0, high = SESSION_SETTING_COUNT - 1;
> +	if (key == NULL)
> +		return 0;
> +	while (low <= high) {
> +		int index = (high + low) / 2;
> +		const char *name = session_setting_strs[index];
> +		int cmp = strcmp(name, key);
> +		if (cmp == 0) {
> +			if (is_including) {
> +				*sid = index;
> +				return 0;
> +			}
> +			*sid = --index;
> +			return index >= 0 ? 0 : -1;
> +		}
> +		if (cmp < 0)
> +			low = index + 1;
> +		else
> +			high = index - 1;
> +	}
> +	if (is_eq) {
> +		*sid = SESSION_SETTING_COUNT;
> +		return -1;
> +	}
> +	assert(low > high);
> +	*sid = high;
> +	return high >= 0 ? 0 : -1;
> +}
> +
>  static int
>  session_settings_next(int *sid, const char *key, bool is_eq, bool is_including)
>  {
> @@ -145,9 +213,15 @@ session_settings_iterator_next(struct iterator *iterator, struct tuple **result)
>  	int sid = it->setting_id;
>  	const char *key = it->key;
>  	bool is_including = it->is_including, is_eq = it->is_eq;
> -	bool is_found = false;
> -	if (session_settings_next(&sid, key, is_eq, is_including) == 0)
> -		is_found = true;
> +	bool is_found;
> +	if (!it->is_set) {
> +		it->is_set = true;
> +		is_found = session_settings_set_forward(&sid, key, is_eq,
> +							is_including) == 0;
> +	} else {
> +		is_found = session_settings_next(&sid, key, is_eq,
> +						 is_including) == 0;
> +	}
>  	it->setting_id = sid + 1;
>  	if (!is_found) {
>  		*result = NULL;
> @@ -167,9 +241,15 @@ session_settings_iterator_prev(struct iterator *iterator, struct tuple **result)
>  	int sid = it->setting_id;
>  	const char *key = it->key;
>  	bool is_including = it->is_including, is_eq = it->is_eq;
> -	bool is_found = false;
> -	if (session_settings_prev(&sid, key, is_eq, is_including) == 0)
> -		is_found = true;
> +	bool is_found;
> +	if (!it->is_set) {
> +		it->is_set = true;
> +		is_found = session_settings_set_reverse(&sid, key, is_eq,
> +							is_including) == 0;
> +	} else {
> +		is_found = session_settings_prev(&sid, key, is_eq,
> +						 is_including) == 0;
> +	}
>  	it->setting_id = sid - 1;
>  	if (!is_found) {
>  		*result = NULL;
> @@ -221,6 +301,7 @@ session_settings_index_create_iterator(struct index *base,
>  	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->is_set = false;
>  	it->format = index->format;
>  	if (!iterator_type_is_reverse(type)) {
>  		it->base.next = session_settings_iterator_next;
> @@ -244,7 +325,7 @@ session_settings_index_get(struct index *base, const char *key,
>  	key = mp_decode_str(&key, &len);
>  	key = tt_cstr(key, len);
>  	int sid = 0;
> -	if (session_settings_next(&sid, key, true, true) != 0) {
> +	if (session_settings_set_forward(&sid, key, true, true) != 0) {
>  		*result = NULL;
>  		return 0;
>  	}
> @@ -345,7 +426,7 @@ session_settings_space_execute_update(struct space *space, struct txn *txn,
>  	}
>  	key = mp_decode_str(&key, &key_len);
>  	key = tt_cstr(key, key_len);
> -	if (session_settings_next(&sid, key, true, true) != 0) {
> +	if (session_settings_set_forward(&sid, key, true, true) != 0) {
>  		*result = NULL;
>  		return 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 ed340d053..bae77192e 100644
> --- a/test/box/gh-4511-access-settings-from-any-frontend.result
> +++ b/test/box/gh-4511-access-settings-from-any-frontend.result
> @@ -82,6 +82,12 @@ function check_sorting(ss, ts, key)
>      for _, it in pairs(iterators_list) do
>          local view_space = ss:select({key}, {iterator = it})
>          local test_space = ts:select({key}, {iterator = it})
> +        if #view_space ~= #test_space then
> +            return {
> +                err = 'bad sorting', type = it, exp = test_space,
> +                got = view_space
> +            }
> +        end
>          for key, value in pairs(view_space) do
>              if test_space[key].name ~= value.name then
>                  return {
> @@ -111,32 +117,37 @@ check_sorting(s, t, 'sql_d')
>  check_sorting(s, t, 'sql_v')
>   | ---
>   | ...
> -check_sorting(s, t, 'sql_defer_foreign_keys')
> +check_sorting(s, t, 'z')
>   | ---
>   | ...
> -
> -t:drop()
> +check_sorting(s, t, 'sql_parser_debuf')
> + | ---
> + | ...
> +check_sorting(s, t, 'sql_parser_debuh')
>   | ---
>   | ...
>  
> --- Check get() method of session_settings space.
> -s:get({'sql_defer_foreign_keys'})
> +name = nil
>   | ---
> - | - ['sql_defer_foreign_keys', false]
>   | ...
> -s:get({'sql_recursive_triggers'})
> +err = nil
>   | ---
> - | - ['sql_recursive_triggers', true]
>   | ...
> -s:get({'sql_reverse_unordered_selects'})
> +for _, tuple in t:pairs() do                    \
> +    name = tuple.name                           \
> +    err = check_sorting(s, t, name)             \
> +    if err then                                 \
> +        break                                   \
> +    end                                         \
> +end
>   | ---
> - | - ['sql_reverse_unordered_selects', false]
>   | ...
> -s:get({'sql_default_engine'})
> +err and {err, name}
>   | ---
> - | - ['sql_default_engine', 'memtx']
> + | - null
>   | ...
> -s:get({'abcd'})
> +
> +t:drop()
>   | ---
>   | ...
>  
> 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 366874998..b243be15e 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
> @@ -36,6 +36,12 @@ function check_sorting(ss, ts, key)
>      for _, it in pairs(iterators_list) do
>          local view_space = ss:select({key}, {iterator = it})
>          local test_space = ts:select({key}, {iterator = it})
> +        if #view_space ~= #test_space then
> +            return {
> +                err = 'bad sorting', type = it, exp = test_space,
> +                got = view_space
> +            }
> +        end
>          for key, value in pairs(view_space) do
>              if test_space[key].name ~= value.name then
>                  return {
> @@ -52,17 +58,23 @@ 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')
> +check_sorting(s, t, 'z')
> +check_sorting(s, t, 'sql_parser_debuf')
> +check_sorting(s, t, 'sql_parser_debuh')
> +
> +name = nil
> +err = nil
> +for _, tuple in t:pairs() do                    \
> +    name = tuple.name                           \
> +    err = check_sorting(s, t, name)             \
> +    if err then                                 \
> +        break                                   \
> +    end                                         \
> +end
> +err and {err, name}
>  
>  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
> -- 
> 2.21.1 (Apple Git-122.3)
> 

Re: [Tarantool-patches] [PATCH 3/4] box: provide a user friendly frontend for accessing session settings

[Nikita Pettik]

On 17 Feb 15:12, Chris Sosnin wrote:
> - space_object:update() is hard to use for configuring session settings,
> so we provide box.session.setting table, which can be used in a much more
> native way.
> 
> - Prior to this patch sql settings were not accessible before box.cfg()
> call, even though these flags can be set right after session creation.
> 
> Part of #4711
> ---

tarantool> box.session.settings.sql_vdbe_debug
---
- false
...

tarantool> box.session.settings.sql_vdbe_debug = true
---
...

tarantool> box.session.settings.sql_vdbe_debug
---
- true
...

tarantool> box.execute("select 1")
---
- metadata:
  - name: '1'
    type: integer
  rows:
  - [1]
...

Looks inconsistent. Can we use instead of :set() method simple
table value assignment? Otherwise accessing row table values
should be disallowed. Same concerns :get() method. Why ever
anyone should bother with :get() when one can access table value
via simple indexing?

Re: [Tarantool-patches] [PATCH 4/4] sql: provide a user friendly frontend for accessing session settings

[Nikita Pettik]

On 17 Feb 15:12, Chris Sosnin wrote:
> Currently if a user wants to change session setting with sql, he has
> to execute non-obvious query, thus, we introduce a more native way to
> do this.

It is not about non-obvious queries, but it is all about documentation:
the better feature is described, the clearer its usage turns out to be
for user.
 
> Closes #4711
> 
> @TarantoolBot document
> Title: API for accessing _session_settings space.
> There are two ways of updating values of session settings:
> via Lua and SQL.
> 
> SQL:
> Instead of typing long UPDATE query one can use the SET statement:
> `box.execute([[SET "<setting_name>" = <new_value>]])`.
> Note, that this query is case sensitive so the name must be quoted.
> 
> Example:
> ```
> tarantool> box.execute([[set "sql_default_engine" = 'memtx']])
> ---
> - row_count: 1
> ...
> 
> tarantool> box.execute([[set "sql_defer_foreign_keys" = true]])

Why didn't you consider show/get command to retrieve setting value?
Otherwise, you simplify way to set session local options, but doesn't
provide the same way to extract current values.

> diff --git a/src/box/sql/sqlInt.h b/src/box/sql/sqlInt.h
> index d1fcf4761..3ffae5970 100644
> --- a/src/box/sql/sqlInt.h
> +++ b/src/box/sql/sqlInt.h
> @@ -4510,4 +4510,15 @@ int
>  sql_fieldno_by_name(struct Parse *parse_context, struct Expr *field_name,
>  		    uint32_t *fieldno);
>  
> diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
> index 620d74e66..c81486fa6 100644
> --- a/src/box/sql/vdbe.c
> +++ b/src/box/sql/vdbe.c
> @@ -55,6 +55,7 @@
>  #include "box/schema.h"
>  #include "box/space.h"
>  #include "box/sequence.h"
> +#include "box/session_settings.h"
>  
>  /*
>   * Invoke this macro on memory cells just prior to changing the
> @@ -5248,6 +5249,55 @@ case OP_IncMaxid: {
>  	break;
>  }
>  
> +/* Opcode: Set P1 P2 * * *
> + *
> + * Set the new value of the session setting. P1 is the id of the
> + * setting in the session_settings array, P2 is the register
> + * holding a value.
> + */
> +case OP_Set: {

Please, use more specific opcode name. Like OP_SettingSet.

Re: [Tarantool-patches] [PATCH 3/4] box: provide a user friendly frontend for accessing session settings

[Vladislav Shpilevoy]

On 16/03/2020 17:08, Nikita Pettik wrote:
> On 17 Feb 15:12, Chris Sosnin wrote:
>> - space_object:update() is hard to use for configuring session settings,
>> so we provide box.session.setting table, which can be used in a much more
>> native way.
>>
>> - Prior to this patch sql settings were not accessible before box.cfg()
>> call, even though these flags can be set right after session creation.
>>
>> Part of #4711
>> ---
> 
> tarantool> box.session.settings.sql_vdbe_debug
> ---
> - false
> ...
> 
> tarantool> box.session.settings.sql_vdbe_debug = true
> ---
> ...
> 
> tarantool> box.session.settings.sql_vdbe_debug
> ---
> - true
> ...

Yeah, we can ban this. To avoid confusion.

> 
> tarantool> box.execute("select 1")
> ---
> - metadata:
>   - name: '1'
>     type: integer
>   rows:
>   - [1]
> ...
> 
> Looks inconsistent. Can we use instead of :set() method simple
> table value assignment? Otherwise accessing row table values

Assignment would require not to store settings in box.session.settings,
to be able to redefine __newindex metamethod. If we don't store them, we
kill autocompletion, which was asked explicitly by somebody.

But I am on your side here - I don't think autocompletion worth this
complication. Who wants to look at existing settings can just print
box.sessions.settings table.

> should be disallowed. Same concerns :get() method. Why ever
> anyone should bother with :get() when one can access table value
> via simple indexing?

Hm. But there is no :get() method. We didn't implement getting, because
no one asked for this. And indeed, usually you just set settings, without
checking if set really worked. I was thinking we could introduce get if
someone asks for that. But up to you. Can be added now as well.

Re: [Tarantool-patches] [PATCH 2/4] box: add binary search for _session_settings space

[Vladislav Shpilevoy]

Hi! Thanks for your comments!

On 16/03/2020 15:16, Nikita Pettik wrote:
> On 17 Feb 15:12, Chris Sosnin wrote:
>> As it is mentioned in implementation, it is important
>> that _session_settings options are sorted by name, so
>> there is no need in linear lookup and we can replace it
>> with binary search.
> 
> Is there any sufficient performance benefit except for code complication?:)
> I really doubt that this part should be optimized for such rare in
> terms of usage place.

We didn't measure perf increase, but for such a simple change it
did not seem necessary.

Talking of rareness of settings change - this is arguable. Firstly,
every new session will change settings, if a user's project uses some
of them permanently. Secondly, some settings, such as default engine,
or constraints related, or similar can be changed on per-request basis,
in case user wants to make some requests not checking FK, and others
should check them, inside one session, for instance. Similar necessity
can arise for other settings. I think we can actually measure how faster
lookup became for that case.

> What is more, there's only dozen entries, so
> binary search doesn't really make any sence. Idk why Kirill assigned 2.4.1

It is only dozen for now. This will change. We already have read-only
session coming.

> milestone, IMHO there are way far more important things to elaborate on.

Honestly, I was thinking there is not much to elaborate. This is
trivial bsearch.

Re: [Tarantool-patches] [PATCH 4/4] sql: provide a user friendly frontend for accessing session settings

[Vladislav Shpilevoy]

On 16/03/2020 18:02, Nikita Pettik wrote:
> On 17 Feb 15:12, Chris Sosnin wrote:
>> Currently if a user wants to change session setting with sql, he has
>> to execute non-obvious query, thus, we introduce a more native way to
>> do this.
> 
> It is not about non-obvious queries, but it is all about documentation:
> the better feature is described, the clearer its usage turns out to be
> for user.

However, on github you voted for this issue, and even agreed that at
least for SQL we need a simpler way to update settings. What changed?

In my opinion, none of system spaces should ever be allowed to be used
by users directly. Especially in such intricate and long way.

>> diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
>> index 620d74e66..c81486fa6 100644
>> --- a/src/box/sql/vdbe.c
>> +++ b/src/box/sql/vdbe.c
>> @@ -5248,6 +5249,55 @@ case OP_IncMaxid: {
>>  	break;
>>  }
>>  
>> +/* Opcode: Set P1 P2 * * *
>> + *
>> + * Set the new value of the session setting. P1 is the id of the
>> + * setting in the session_settings array, P2 is the register
>> + * holding a value.
>> + */
>> +case OP_Set: {
> 
> Please, use more specific opcode name. Like OP_SettingSet.

Should not we then change the grammar? Because it requires just SET to
change a session setting. Not SET SETTING.

Re: [Tarantool-patches] [PATCH 3/4] box: provide a user friendly frontend for accessing session settings

[Nikita Pettik]

On 16 Mar 23:53, Vladislav Shpilevoy wrote:
> On 16/03/2020 17:08, Nikita Pettik wrote:
> > On 17 Feb 15:12, Chris Sosnin wrote:
> >> - space_object:update() is hard to use for configuring session settings,
> >> so we provide box.session.setting table, which can be used in a much more
> >> native way.
> >>
> >> - Prior to this patch sql settings were not accessible before box.cfg()
> >> call, even though these flags can be set right after session creation.
> >>
> >> Part of #4711
> >> ---
> > 
> > tarantool> box.session.settings.sql_vdbe_debug
> > ---
> > - false
> > ...
> > 
> > tarantool> box.session.settings.sql_vdbe_debug = true
> > ---
> > ...
> > 
> > tarantool> box.session.settings.sql_vdbe_debug
> > ---
> > - true
> > ...
> 
> Yeah, we can ban this. To avoid confusion.
> 
> > 
> > tarantool> box.execute("select 1")
> > ---
> > - metadata:
> >   - name: '1'
> >     type: integer
> >   rows:
> >   - [1]
> > ...
> > 
> > Looks inconsistent. Can we use instead of :set() method simple
> > table value assignment? Otherwise accessing row table values
> 
> Assignment would require not to store settings in box.session.settings,
> to be able to redefine __newindex metamethod. If we don't store them, we
> kill autocompletion, which was asked explicitly by somebody.
> 
> But I am on your side here - I don't think autocompletion worth this
> complication. Who wants to look at existing settings can just print
> box.sessions.settings table.
> 
> > should be disallowed. Same concerns :get() method. Why ever
> > anyone should bother with :get() when one can access table value
> > via simple indexing?
> 
> Hm. But there is no :get() method. We didn't implement getting, because
> no one asked for this.

As far as I remember no one either asked for :set() method (except for me) :)

> And indeed, usually you just set settings, without
> checking if set really worked. I was thinking we could introduce get if
> someone asks for that. But up to you. Can be added now as well.

I do not insist since do not consider this to be prio1 task (as well
as any other issue connected with settings machinery).

Re: [Tarantool-patches] [PATCH 3/4] box: provide a user friendly frontend for accessing session settings

[Chris Sosnin]

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> On 17 Mar 2020, at 17:27, Nikita Pettik <korablev@tarantool.org> wrote:
> 
> On 16 Mar 23:53, Vladislav Shpilevoy wrote:
>> On 16/03/2020 17:08, Nikita Pettik wrote:
>>> On 17 Feb 15:12, Chris Sosnin wrote:
>>>> - space_object:update() is hard to use for configuring session settings,
>>>> so we provide box.session.setting table, which can be used in a much more
>>>> native way.
>>>> 
>>>> - Prior to this patch sql settings were not accessible before box.cfg()
>>>> call, even though these flags can be set right after session creation.
>>>> 
>>>> Part of #4711
>>>> ---
>>> 
>>> tarantool> box.session.settings.sql_vdbe_debug
>>> ---
>>> - false
>>> ...
>>> 
>>> tarantool> box.session.settings.sql_vdbe_debug = true
>>> ---
>>> ...
>>> 
>>> tarantool> box.session.settings.sql_vdbe_debug
>>> ---
>>> - true
>>> ...
>> 
>> Yeah, we can ban this. To avoid confusion.
>> 
>>> 
>>> tarantool> box.execute("select 1")
>>> ---
>>> - metadata:
>>>  - name: '1'
>>>    type: integer
>>>  rows:
>>>  - [1]
>>> ...
>>> 
>>> Looks inconsistent. Can we use instead of :set() method simple
>>> table value assignment? Otherwise accessing row table values
>> 
>> Assignment would require not to store settings in box.session.settings,
>> to be able to redefine __newindex metamethod. If we don't store them, we
>> kill autocompletion, which was asked explicitly by somebody.
>> 
>> But I am on your side here - I don't think autocompletion worth this
>> complication. Who wants to look at existing settings can just print
>> box.sessions.settings table.
>> 
>>> should be disallowed. Same concerns :get() method. Why ever
>>> anyone should bother with :get() when one can access table value
>>> via simple indexing?
>> 
>> Hm. But there is no :get() method. We didn't implement getting, because
>> no one asked for this.
> 
> As far as I remember no one either asked for :set() method (except for me) :)

This method is a workaround to allow console autocompletion, Lua doesn’t allow you to overload
indexing for the keys already present in the table. But here I agree that this implementation is rather
misleading. I will rework the patch to allow settings.<name> = <value> syntax.

> 
>> And indeed, usually you just set settings, without
>> checking if set really worked. I was thinking we could introduce get if
>> someone asks for that. But up to you. Can be added now as well.
> 
> I do not insist since do not consider this to be prio1 task (as well
> as any other issue connected with settings machinery).


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Re: [Tarantool-patches] [PATCH 2/4] box: add binary search for _session_settings space

[Nikita Pettik]

On 16 Mar 23:53, Vladislav Shpilevoy wrote:
> Hi! Thanks for your comments!
> 
> On 16/03/2020 15:16, Nikita Pettik wrote:
> > On 17 Feb 15:12, Chris Sosnin wrote:
> >> As it is mentioned in implementation, it is important
> >> that _session_settings options are sorted by name, so
> >> there is no need in linear lookup and we can replace it
> >> with binary search.
> > 
> > Is there any sufficient performance benefit except for code complication?:)
> > I really doubt that this part should be optimized for such rare in
> > terms of usage place.
> 
> We didn't measure perf increase, but for such a simple change it
> did not seem necessary.

I mean there can be no even performance benefit at all since
binary search on small data sets can be slower than sequential
access (there's linear search mode even in bps tree, but it is
compile time option).
 
> Talking of rareness of settings change - this is arguable. Firstly,
> every new session will change settings, if a user's project uses some
> of them permanently. Secondly, some settings, such as default engine,
> or constraints related, or similar can be changed on per-request basis,
> in case user wants to make some requests not checking FK, and others
> should check them, inside one session, for instance. Similar necessity
> can arise for other settings. I think we can actually measure how faster
> lookup became for that case.
> 
> > What is more, there's only dozen entries, so
> > binary search doesn't really make any sence. Idk why Kirill assigned 2.4.1
> 
> It is only dozen for now. This will change. We already have read-only
> session coming.
> 
> > milestone, IMHO there are way far more important things to elaborate on.
> 
> Honestly, I was thinking there is not much to elaborate. This is
> trivial bsearch.

I mean work on more improtant features or/and severe bugs. Nevermind,
it is already done anyway. Personally I would reject this patch if
there's no any performance increase (otherwise, it simply complicates
code).

Re: [Tarantool-patches] [PATCH 4/4] sql: provide a user friendly frontend for accessing session settings

[Chris Sosnin]

> On 16 Mar 2020, at 20:02, Nikita Pettik <korablev@tarantool.org> wrote:
> 
> On 17 Feb 15:12, Chris Sosnin wrote:
>> Currently if a user wants to change session setting with sql, he has
>> to execute non-obvious query, thus, we introduce a more native way to
>> do this.
> 
> It is not about non-obvious queries, but it is all about documentation:
> the better feature is described, the clearer its usage turns out to be
> for user.

Should I change the commit message? I though this patchset is about simplifying
the way session settings are updated?

> 
>> Closes #4711
>> 
>> @TarantoolBot document
>> Title: API for accessing _session_settings space.
>> There are two ways of updating values of session settings:
>> via Lua and SQL.
>> 
>> SQL:
>> Instead of typing long UPDATE query one can use the SET statement:
>> `box.execute([[SET "<setting_name>" = <new_value>]])`.
>> Note, that this query is case sensitive so the name must be quoted.
>> 
>> Example:
>> ```
>> tarantool> box.execute([[set "sql_default_engine" = 'memtx']])
>> ---
>> - row_count: 1
>> ...
>> 
>> tarantool> box.execute([[set "sql_defer_foreign_keys" = true]])
> 
> Why didn't you consider show/get command to retrieve setting value?
> Otherwise, you simplify way to set session local options, but doesn't
> provide the same way to extract current values.

SELECT * FROM “_session_settings” is simple enough, isn’t it?

> 
>> diff --git a/src/box/sql/sqlInt.h b/src/box/sql/sqlInt.h
>> index d1fcf4761..3ffae5970 100644
>> --- a/src/box/sql/sqlInt.h
>> +++ b/src/box/sql/sqlInt.h
>> @@ -4510,4 +4510,15 @@ int
>> sql_fieldno_by_name(struct Parse *parse_context, struct Expr *field_name,
>> 		    uint32_t *fieldno);
>> 
>> diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
>> index 620d74e66..c81486fa6 100644
>> --- a/src/box/sql/vdbe.c
>> +++ b/src/box/sql/vdbe.c
>> @@ -55,6 +55,7 @@
>> #include "box/schema.h"
>> #include "box/space.h"
>> #include "box/sequence.h"
>> +#include "box/session_settings.h"
>> 
>> /*
>>  * Invoke this macro on memory cells just prior to changing the
>> @@ -5248,6 +5249,55 @@ case OP_IncMaxid: {
>> 	break;
>> }
>> 
>> +/* Opcode: Set P1 P2 * * *
>> + *
>> + * Set the new value of the session setting. P1 is the id of the
>> + * setting in the session_settings array, P2 is the register
>> + * holding a value.
>> + */
>> +case OP_Set: {
> 
> Please, use more specific opcode name. Like OP_SettingSet.

Didn’t we accept ’set’ syntax?

> 

Re: [Tarantool-patches] [PATCH 4/4] sql: provide a user friendly frontend for accessing session settings

[Nikita Pettik]

On 17 Mar 20:26, Chris Sosnin wrote:
> 
> 
> > On 16 Mar 2020, at 20:02, Nikita Pettik <korablev@tarantool.org> wrote:
> > 
> > On 17 Feb 15:12, Chris Sosnin wrote:
> >> Currently if a user wants to change session setting with sql, he has
> >> to execute non-obvious query, thus, we introduce a more native way to
> >> do this.
> > 
> > It is not about non-obvious queries, but it is all about documentation:
> > the better feature is described, the clearer its usage turns out to be
> > for user.
> 
> Should I change the commit message? I though this patchset is about simplifying
> the way session settings are updated?

I would say:

Currently if a user wants to change session settings via SQL, one has
to execute UPDATE query like:
[[UPDATE "_session_settings" SET "value" = true WHERE "name" = 'name']]
However, direct access to system spaces isn't considered to be good practice.
To avoid that and a bit simplify user's life, we introduce SQL shortcut command
SET with following syntax: SET <setting_name> = <value>. <setting_name> is
supposed to be name of setting (note that it is uppercased as any other
non-quoted indentifiers in SQL) and <value> - value of corresponding setting to
be set; <value> should be either literal or binding marker. Also it is worth
noting that SET doesn't provide any implicit casts, so <value> must be of the
type corresponding to the setting being updated. 

Example:
...

^ It is up to you.
 
> > 
> >> Closes #4711
> >> 
> >> @TarantoolBot document
> >> Title: API for accessing _session_settings space.
> >> There are two ways of updating values of session settings:
> >> via Lua and SQL.
> >> 
> >> SQL:
> >> Instead of typing long UPDATE query one can use the SET statement:
> >> `box.execute([[SET "<setting_name>" = <new_value>]])`.
> >> Note, that this query is case sensitive so the name must be quoted.
> >> 
> >> Example:
> >> ```
> >> tarantool> box.execute([[set "sql_default_engine" = 'memtx']])
> >> ---
> >> - row_count: 1
> >> ...
> >> 
> >> tarantool> box.execute([[set "sql_defer_foreign_keys" = true]])
> > 
> > Why didn't you consider show/get command to retrieve setting value?
> > Otherwise, you simplify way to set session local options, but doesn't
> > provide the same way to extract current values.
> 
> SELECT * FROM “_session_settings” is simple enough, isn’t it?

In this case you'll get list of all settings. To get specific one
we should use this query:

SELECT value FROM "_session_settings" WHERE "name" = 'xxx'

I do not insist on implementing GET/SHOW SQL syntax now tho.

> >> diff --git a/src/box/sql/sqlInt.h b/src/box/sql/sqlInt.h
> >> index d1fcf4761..3ffae5970 100644
> >> --- a/src/box/sql/sqlInt.h
> >> +++ b/src/box/sql/sqlInt.h
> >> @@ -4510,4 +4510,15 @@ int
> >> sql_fieldno_by_name(struct Parse *parse_context, struct Expr *field_name,
> >> 		    uint32_t *fieldno);
> >> 
> >> diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
> >> index 620d74e66..c81486fa6 100644
> >> --- a/src/box/sql/vdbe.c
> >> +++ b/src/box/sql/vdbe.c
> >> @@ -55,6 +55,7 @@
> >> #include "box/schema.h"
> >> #include "box/space.h"
> >> #include "box/sequence.h"
> >> +#include "box/session_settings.h"
> >> 
> >> /*
> >>  * Invoke this macro on memory cells just prior to changing the
> >> @@ -5248,6 +5249,55 @@ case OP_IncMaxid: {
> >> 	break;
> >> }
> >> 
> >> +/* Opcode: Set P1 P2 * * *
> >> + *
> >> + * Set the new value of the session setting. P1 is the id of the
> >> + * setting in the session_settings array, P2 is the register
> >> + * holding a value.
> >> + */
> >> +case OP_Set: {
> > 
> > Please, use more specific opcode name. Like OP_SettingSet.
> 
> Didn’t we accept ’set’ syntax?

SET is okay, but I don't mind SET SETTING as well. OP_Set is too general
name - SET keyword is also part of UPDATE syntax, so it may confuse other
developers. Except for this nit patch LGTM.

Re: [Tarantool-patches] [PATCH 4/4] sql: provide a user friendly frontend for accessing session settings

[Chris Sosnin]

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Thank you for your answers!

> On 17 Mar 2020, at 23:12, Nikita Pettik <korablev@tarantool.org> wrote:
> 
> On 17 Mar 20:26, Chris Sosnin wrote:
>> 
>> 
>>> On 16 Mar 2020, at 20:02, Nikita Pettik <korablev@tarantool.org> wrote:
>>> 
>>> On 17 Feb 15:12, Chris Sosnin wrote:
>>>> Currently if a user wants to change session setting with sql, he has
>>>> to execute non-obvious query, thus, we introduce a more native way to
>>>> do this.
>>> 
>>> It is not about non-obvious queries, but it is all about documentation:
>>> the better feature is described, the clearer its usage turns out to be
>>> for user.
>> 
>> Should I change the commit message? I though this patchset is about simplifying
>> the way session settings are updated?
> 
> I would say:
> 
> Currently if a user wants to change session settings via SQL, one has
> to execute UPDATE query like:
> [[UPDATE "_session_settings" SET "value" = true WHERE "name" = 'name']]
> However, direct access to system spaces isn't considered to be good practice.
> To avoid that and a bit simplify user's life, we introduce SQL shortcut command
> SET with following syntax: SET <setting_name> = <value>. <setting_name> is
> supposed to be name of setting (note that it is uppercased as any other
> non-quoted indentifiers in SQL) and <value> - value of corresponding setting to
> be set; <value> should be either literal or binding marker. Also it is worth
> noting that SET doesn't provide any implicit casts, so <value> must be of the
> type corresponding to the setting being updated. 
> 
> Example:
> ...
> 
> ^ It is up to you.
> 
>>> 
>>>> Closes #4711
>>>> 
>>>> @TarantoolBot document
>>>> Title: API for accessing _session_settings space.
>>>> There are two ways of updating values of session settings:
>>>> via Lua and SQL.
>>>> 
>>>> SQL:
>>>> Instead of typing long UPDATE query one can use the SET statement:
>>>> `box.execute([[SET "<setting_name>" = <new_value>]])`.
>>>> Note, that this query is case sensitive so the name must be quoted.
>>>> 
>>>> Example:
>>>> ```
>>>> tarantool> box.execute([[set "sql_default_engine" = 'memtx']])
>>>> ---
>>>> - row_count: 1
>>>> ...
>>>> 
>>>> tarantool> box.execute([[set "sql_defer_foreign_keys" = true]])
>>> 
>>> Why didn't you consider show/get command to retrieve setting value?
>>> Otherwise, you simplify way to set session local options, but doesn't
>>> provide the same way to extract current values.
>> 
>> SELECT * FROM “_session_settings” is simple enough, isn’t it?
> 
> In this case you'll get list of all settings. To get specific one
> we should use this query:
> 
> SELECT value FROM "_session_settings" WHERE "name" = 'xxx'
> 
> I do not insist on implementing GET/SHOW SQL syntax now tho.
> 
>>>> diff --git a/src/box/sql/sqlInt.h b/src/box/sql/sqlInt.h
>>>> index d1fcf4761..3ffae5970 100644
>>>> --- a/src/box/sql/sqlInt.h
>>>> +++ b/src/box/sql/sqlInt.h
>>>> @@ -4510,4 +4510,15 @@ int
>>>> sql_fieldno_by_name(struct Parse *parse_context, struct Expr *field_name,
>>>> 		    uint32_t *fieldno);
>>>> 
>>>> diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
>>>> index 620d74e66..c81486fa6 100644
>>>> --- a/src/box/sql/vdbe.c
>>>> +++ b/src/box/sql/vdbe.c
>>>> @@ -55,6 +55,7 @@
>>>> #include "box/schema.h"
>>>> #include "box/space.h"
>>>> #include "box/sequence.h"
>>>> +#include "box/session_settings.h"
>>>> 
>>>> /*
>>>> * Invoke this macro on memory cells just prior to changing the
>>>> @@ -5248,6 +5249,55 @@ case OP_IncMaxid: {
>>>> 	break;
>>>> }
>>>> 
>>>> +/* Opcode: Set P1 P2 * * *
>>>> + *
>>>> + * Set the new value of the session setting. P1 is the id of the
>>>> + * setting in the session_settings array, P2 is the register
>>>> + * holding a value.
>>>> + */
>>>> +case OP_Set: {
>>> 
>>> Please, use more specific opcode name. Like OP_SettingSet.
>> 
>> Didn’t we accept ’set’ syntax?
> 
> SET is okay, but I don't mind SET SETTING as well. OP_Set is too general
> name - SET keyword is also part of UPDATE syntax, so it may confuse other
> developers. Except for this nit patch LGTM.

I don’t mind this changes, I will work on them tomorrow.


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Re: [Tarantool-patches] [PATCH 4/4] sql: provide a user friendly frontend for accessing session settings

[Chris Sosnin]

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> On 17 Mar 2020, at 23:12, Nikita Pettik <korablev@tarantool.org> wrote:
> 
> On 17 Mar 20:26, Chris Sosnin wrote:
>> 
>> 
>>> On 16 Mar 2020, at 20:02, Nikita Pettik <korablev@tarantool.org> wrote:
>>> 
>>> On 17 Feb 15:12, Chris Sosnin wrote:
>>>> Currently if a user wants to change session setting with sql, he has
>>>> to execute non-obvious query, thus, we introduce a more native way to
>>>> do this.
>>> 
>>> It is not about non-obvious queries, but it is all about documentation:
>>> the better feature is described, the clearer its usage turns out to be
>>> for user.
>> 
>> Should I change the commit message? I though this patchset is about simplifying
>> the way session settings are updated?
> 
> I would say:
> 
> Currently if a user wants to change session settings via SQL, one has
> to execute UPDATE query like:
> [[UPDATE "_session_settings" SET "value" = true WHERE "name" = 'name']]
> However, direct access to system spaces isn't considered to be good practice.
> To avoid that and a bit simplify user's life, we introduce SQL shortcut command
> SET with following syntax: SET <setting_name> = <value>. <setting_name> is
> supposed to be name of setting (note that it is uppercased as any other
> non-quoted indentifiers in SQL) and <value> - value of corresponding setting to
> be set; <value> should be either literal or binding marker. Also it is worth
> noting that SET doesn't provide any implicit casts, so <value> must be of the
> type corresponding to the setting being updated. 
> 
> Example:
> ...
> 
> ^ It is up to you.

I took the beginning as long as the rest is described in the doc request (except for
implicit casts note, thanks for pointing that out, fixed):

Currently if a user wants to change session setting with SQL, one has
to execute UPDATE query like:
[[UPDATE "_session_settings" SET "value" = true WHERE "name" = 'name']]
However, direct access to system spaces isn't considered to be a good practice.
To avoid that and a bit simplify user's life, we introduce SQL shortcut command
SETTING SET.

> 
>>> 
>>>> Closes #4711
>>>> 
>>>> @TarantoolBot document
>>>> Title: API for accessing _session_settings space.
>>>> There are two ways of updating values of session settings:
>>>> via Lua and SQL.
>>>> 
>>>> SQL:
>>>> Instead of typing long UPDATE query one can use the SET statement:
>>>> `box.execute([[SET "<setting_name>" = <new_value>]])`.
>>>> Note, that this query is case sensitive so the name must be quoted.
>>>> 
>>>> Example:
>>>> ```
>>>> tarantool> box.execute([[set "sql_default_engine" = 'memtx']])
>>>> ---
>>>> - row_count: 1
>>>> ...
>>>> 
>>>> tarantool> box.execute([[set "sql_defer_foreign_keys" = true]])
>>> 
>>> Why didn't you consider show/get command to retrieve setting value?
>>> Otherwise, you simplify way to set session local options, but doesn't
>>> provide the same way to extract current values.
>> 
>> SELECT * FROM “_session_settings” is simple enough, isn’t it?
> 
> In this case you'll get list of all settings. To get specific one
> we should use this query:
> 
> SELECT value FROM "_session_settings" WHERE "name" = 'xxx'
> 
> I do not insist on implementing GET/SHOW SQL syntax now tho.
> 
>>>> diff --git a/src/box/sql/sqlInt.h b/src/box/sql/sqlInt.h
>>>> index d1fcf4761..3ffae5970 100644
>>>> --- a/src/box/sql/sqlInt.h
>>>> +++ b/src/box/sql/sqlInt.h
>>>> @@ -4510,4 +4510,15 @@ int
>>>> sql_fieldno_by_name(struct Parse *parse_context, struct Expr *field_name,
>>>> 		    uint32_t *fieldno);
>>>> 
>>>> diff --git a/src/box/sql/vdbe.c b/src/box/sql/vdbe.c
>>>> index 620d74e66..c81486fa6 100644
>>>> --- a/src/box/sql/vdbe.c
>>>> +++ b/src/box/sql/vdbe.c
>>>> @@ -55,6 +55,7 @@
>>>> #include "box/schema.h"
>>>> #include "box/space.h"
>>>> #include "box/sequence.h"
>>>> +#include "box/session_settings.h"
>>>> 
>>>> /*
>>>> * Invoke this macro on memory cells just prior to changing the
>>>> @@ -5248,6 +5249,55 @@ case OP_IncMaxid: {
>>>> 	break;
>>>> }
>>>> 
>>>> +/* Opcode: Set P1 P2 * * *
>>>> + *
>>>> + * Set the new value of the session setting. P1 is the id of the
>>>> + * setting in the session_settings array, P2 is the register
>>>> + * holding a value.
>>>> + */
>>>> +case OP_Set: {
>>> 
>>> Please, use more specific opcode name. Like OP_SettingSet.
>> 
>> Didn’t we accept ’set’ syntax?
> 
> SET is okay, but I don't mind SET SETTING as well. OP_Set is too general
> name - SET keyword is also part of UPDATE syntax, so it may confuse other
> developers. Except for this nit patch LGTM.


Here are the fixes:

-               sqlVdbeAddOp2(vdbe, OP_Set, index, target);
+              sqlVdbeAddOp2(vdbe, OP_SetSetting, index, target);

-///////////////////////////// The SET command ////////////////////////////////
-cmd ::= SET nm(X) EQ expr(Y).  {
+///////////////////////////// The SETTING SET command ////////////////////////
+cmd ::= SETTING SET nm(X) EQ expr(Y).  {

-/* Opcode: Set P1 P2 * * *
+/* Opcode: SetSetting P1 P2 * * *

-case OP_Set: {
+case OP_SetSetting: {

And of course I had to change the grammar and tests.

Changes are on the branch with the second version of Lua patch:
https://github.com/tarantool/tarantool/tree/ksosnin/gh-4712-session-settings-v2

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Re: [Tarantool-patches] [PATCH 2/4] box: add binary search for _session_settings space

[Kirill Yukhin]

Hello,

On 03 Apr 14:00, Nikita Pettik wrote:
> On 30 Mar 12:13, Chris Sosnin wrote:
> > As it is mentioned in implementation, it is important
> > that _session_settings options are sorted by name, so
> > there is no need in linear lookup and we can replace it
> > with binary search.
> > 
> > Closes #4712
> > ---
> 
> Still I see no need for this patch. It is unclear which improvements
> it introduces except for code complication.

I agree, let's drop it.

--
Regards, Kirill Yukhin

Re: [Tarantool-patches] [PATCH 2/4] box: add binary search for _session_settings space

[Nikita Pettik]

On 30 Mar 12:13, Chris Sosnin wrote:
> As it is mentioned in implementation, it is important
> that _session_settings options are sorted by name, so
> there is no need in linear lookup and we can replace it
> with binary search.
> 
> Closes #4712
> ---

Still I see no need for this patch. It is unclear which improvements
it introduces except for code complication.
 
> diff --git a/src/box/session_settings.c b/src/box/session_settings.c
> index 2ecf71f2d..5e4a50427 100644
> --- a/src/box/session_settings.c
> +++ b/src/box/session_settings.c
> @@ -81,6 +81,8 @@ struct session_settings_iterator {
>  	bool is_eq;
>  	/** True if the iterator should include equal keys. */
>  	bool is_including;
> +	/** True if the iterator is pointing to an existing setting */
> +	bool is_set;
>  };
>  
>  static void
> @@ -92,6 +94,72 @@ session_settings_iterator_free(struct iterator *ptr)
>  	free(it);
>  }
>  
> +static int
> +session_settings_set_forward(int *sid, const char *key, bool is_eq,
> +			     bool is_including)
> +{
> +	int low = 0, high = SESSION_SETTING_COUNT - 1;
> +	if (key == NULL)
> +		return 0;
> +	while (low <= high) {
> +		int index = (high + low) / 2;
> +		const char *name = session_setting_strs[index];
> +		int cmp = strcmp(name, key);
> +		if (cmp == 0) {
> +			if (is_including) {
> +				*sid = index;
> +				return 0;
> +			}
> +			*sid = ++index;
> +			return index < SESSION_SETTING_COUNT ? 0 : -1;
> +		}
> +		if (cmp < 0)
> +			low = index + 1;
> +		else
> +			high = index - 1;
> +	}
> +	if (is_eq) {
> +		*sid = SESSION_SETTING_COUNT;
> +		return -1;
> +	}
> +	assert(low > high);
> +	*sid = low;
> +	return low < SESSION_SETTING_COUNT ? 0 : -1;
> +}
> +
> +static int
> +session_settings_set_reverse(int *sid, const char *key, bool is_eq,
> +			     bool is_including)
> +{
> +	int low = 0, high = SESSION_SETTING_COUNT - 1;
> +	if (key == NULL)
> +		return 0;
> +	while (low <= high) {
> +		int index = (high + low) / 2;
> +		const char *name = session_setting_strs[index];
> +		int cmp = strcmp(name, key);
> +		if (cmp == 0) {
> +			if (is_including) {
> +				*sid = index;
> +				return 0;
> +			}
> +			*sid = --index;
> +			return index >= 0 ? 0 : -1;
> +		}
> +		if (cmp < 0)
> +			low = index + 1;
> +		else
> +			high = index - 1;
> +	}
> +	if (is_eq) {
> +		*sid = SESSION_SETTING_COUNT;
> +		return -1;
> +	}
> +	assert(low > high);
> +	*sid = high;
> +	return high >= 0 ? 0 : -1;
> +}
> +
>  static int
>  session_settings_next(int *sid, const char *key, bool is_eq, bool is_including)
>  {
> @@ -145,9 +213,15 @@ session_settings_iterator_next(struct iterator *iterator, struct tuple **result)
>  	int sid = it->setting_id;
>  	const char *key = it->key;
>  	bool is_including = it->is_including, is_eq = it->is_eq;
> -	bool is_found = false;
> -	if (session_settings_next(&sid, key, is_eq, is_including) == 0)
> -		is_found = true;
> +	bool is_found;
> +	if (!it->is_set) {
> +		it->is_set = true;
> +		is_found = session_settings_set_forward(&sid, key, is_eq,
> +							is_including) == 0;
> +	} else {
> +		is_found = session_settings_next(&sid, key, is_eq,
> +						 is_including) == 0;
> +	}
>  	it->setting_id = sid + 1;
>  	if (!is_found) {
>  		*result = NULL;
> @@ -167,9 +241,15 @@ session_settings_iterator_prev(struct iterator *iterator, struct tuple **result)
>  	int sid = it->setting_id;
>  	const char *key = it->key;
>  	bool is_including = it->is_including, is_eq = it->is_eq;
> -	bool is_found = false;
> -	if (session_settings_prev(&sid, key, is_eq, is_including) == 0)
> -		is_found = true;
> +	bool is_found;
> +	if (!it->is_set) {
> +		it->is_set = true;
> +		is_found = session_settings_set_reverse(&sid, key, is_eq,
> +							is_including) == 0;
> +	} else {
> +		is_found = session_settings_prev(&sid, key, is_eq,
> +						 is_including) == 0;
> +	}
>  	it->setting_id = sid - 1;
>  	if (!is_found) {
>  		*result = NULL;
> @@ -221,6 +301,7 @@ session_settings_index_create_iterator(struct index *base,
>  	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->is_set = false;
>  	it->format = index->format;
>  	if (!iterator_type_is_reverse(type)) {
>  		it->base.next = session_settings_iterator_next;
> @@ -244,7 +325,7 @@ session_settings_index_get(struct index *base, const char *key,
>  	key = mp_decode_str(&key, &len);
>  	key = tt_cstr(key, len);
>  	int sid = 0;
> -	if (session_settings_next(&sid, key, true, true) != 0) {
> +	if (session_settings_set_forward(&sid, key, true, true) != 0) {
>  		*result = NULL;
>  		return 0;
>  	}
> @@ -345,7 +426,7 @@ session_settings_space_execute_update(struct space *space, struct txn *txn,
>  	}
>  	key = mp_decode_str(&key, &key_len);
>  	key = tt_cstr(key, key_len);
> -	if (session_settings_next(&sid, key, true, true) != 0) {
> +	if (session_settings_set_forward(&sid, key, true, true) != 0) {
>  		*result = NULL;
>  		return 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 ed340d053..bae77192e 100644
> --- a/test/box/gh-4511-access-settings-from-any-frontend.result
> +++ b/test/box/gh-4511-access-settings-from-any-frontend.result
> @@ -82,6 +82,12 @@ function check_sorting(ss, ts, key)
>      for _, it in pairs(iterators_list) do
>          local view_space = ss:select({key}, {iterator = it})
>          local test_space = ts:select({key}, {iterator = it})
> +        if #view_space ~= #test_space then
> +            return {
> +                err = 'bad sorting', type = it, exp = test_space,
> +                got = view_space
> +            }
> +        end
>          for key, value in pairs(view_space) do
>              if test_space[key].name ~= value.name then
>                  return {
> @@ -111,32 +117,37 @@ check_sorting(s, t, 'sql_d')
>  check_sorting(s, t, 'sql_v')
>   | ---
>   | ...
> -check_sorting(s, t, 'sql_defer_foreign_keys')
> +check_sorting(s, t, 'z')
>   | ---
>   | ...
> -
> -t:drop()
> +check_sorting(s, t, 'sql_parser_debuf')
> + | ---
> + | ...
> +check_sorting(s, t, 'sql_parser_debuh')
>   | ---
>   | ...
>  
> --- Check get() method of session_settings space.
> -s:get({'sql_defer_foreign_keys'})
> +name = nil
>   | ---
> - | - ['sql_defer_foreign_keys', false]
>   | ...
> -s:get({'sql_recursive_triggers'})
> +err = nil
>   | ---
> - | - ['sql_recursive_triggers', true]
>   | ...
> -s:get({'sql_reverse_unordered_selects'})
> +for _, tuple in t:pairs() do                    \
> +    name = tuple.name                           \
> +    err = check_sorting(s, t, name)             \
> +    if err then                                 \
> +        break                                   \
> +    end                                         \
> +end
>   | ---
> - | - ['sql_reverse_unordered_selects', false]
>   | ...
> -s:get({'sql_default_engine'})
> +err and {err, name}
>   | ---
> - | - ['sql_default_engine', 'memtx']
> + | - null
>   | ...
> -s:get({'abcd'})
> +
> +t:drop()
>   | ---
>   | ...
>  
> 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 366874998..b243be15e 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
> @@ -36,6 +36,12 @@ function check_sorting(ss, ts, key)
>      for _, it in pairs(iterators_list) do
>          local view_space = ss:select({key}, {iterator = it})
>          local test_space = ts:select({key}, {iterator = it})
> +        if #view_space ~= #test_space then
> +            return {
> +                err = 'bad sorting', type = it, exp = test_space,
> +                got = view_space
> +            }
> +        end
>          for key, value in pairs(view_space) do
>              if test_space[key].name ~= value.name then
>                  return {
> @@ -52,17 +58,23 @@ 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')
> +check_sorting(s, t, 'z')
> +check_sorting(s, t, 'sql_parser_debuf')
> +check_sorting(s, t, 'sql_parser_debuh')
> +
> +name = nil
> +err = nil
> +for _, tuple in t:pairs() do                    \
> +    name = tuple.name                           \
> +    err = check_sorting(s, t, name)             \
> +    if err then                                 \
> +        break                                   \
> +    end                                         \
> +end
> +err and {err, name}
>  
>  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
> -- 
> 2.21.1 (Apple Git-122.3)
> 

[Tarantool-patches] [PATCH 2/4] box: add binary search for _session_settings space

[Chris Sosnin]

As it is mentioned in implementation, it is important
that _session_settings options are sorted by name, so
there is no need in linear lookup and we can replace it
with binary search.

Closes #4712
---
 src/box/session_settings.c                    | 97 +++++++++++++++++--
 ...1-access-settings-from-any-frontend.result | 37 ++++---
 ...access-settings-from-any-frontend.test.lua | 28 ++++--
 3 files changed, 133 insertions(+), 29 deletions(-)

diff --git a/src/box/session_settings.c b/src/box/session_settings.c
index 2ecf71f2d..5e4a50427 100644
--- a/src/box/session_settings.c
+++ b/src/box/session_settings.c
@@ -81,6 +81,8 @@ struct session_settings_iterator {
 	bool is_eq;
 	/** True if the iterator should include equal keys. */
 	bool is_including;
+	/** True if the iterator is pointing to an existing setting */
+	bool is_set;
 };
 
 static void
@@ -92,6 +94,72 @@ session_settings_iterator_free(struct iterator *ptr)
 	free(it);
 }
 
+static int
+session_settings_set_forward(int *sid, const char *key, bool is_eq,
+			     bool is_including)
+{
+	int low = 0, high = SESSION_SETTING_COUNT - 1;
+	if (key == NULL)
+		return 0;
+	while (low <= high) {
+		int index = (high + low) / 2;
+		const char *name = session_setting_strs[index];
+		int cmp = strcmp(name, key);
+		if (cmp == 0) {
+			if (is_including) {
+				*sid = index;
+				return 0;
+			}
+			*sid = ++index;
+			return index < SESSION_SETTING_COUNT ? 0 : -1;
+		}
+		if (cmp < 0)
+			low = index + 1;
+		else
+			high = index - 1;
+	}
+	if (is_eq) {
+		*sid = SESSION_SETTING_COUNT;
+		return -1;
+	}
+	assert(low > high);
+	*sid = low;
+	return low < SESSION_SETTING_COUNT ? 0 : -1;
+}
+
+static int
+session_settings_set_reverse(int *sid, const char *key, bool is_eq,
+			     bool is_including)
+{
+	int low = 0, high = SESSION_SETTING_COUNT - 1;
+	if (key == NULL)
+		return 0;
+	while (low <= high) {
+		int index = (high + low) / 2;
+		const char *name = session_setting_strs[index];
+		int cmp = strcmp(name, key);
+		if (cmp == 0) {
+			if (is_including) {
+				*sid = index;
+				return 0;
+			}
+			*sid = --index;
+			return index >= 0 ? 0 : -1;
+		}
+		if (cmp < 0)
+			low = index + 1;
+		else
+			high = index - 1;
+	}
+	if (is_eq) {
+		*sid = SESSION_SETTING_COUNT;
+		return -1;
+	}
+	assert(low > high);
+	*sid = high;
+	return high >= 0 ? 0 : -1;
+}
+
 static int
 session_settings_next(int *sid, const char *key, bool is_eq, bool is_including)
 {
@@ -145,9 +213,15 @@ session_settings_iterator_next(struct iterator *iterator, struct tuple **result)
 	int sid = it->setting_id;
 	const char *key = it->key;
 	bool is_including = it->is_including, is_eq = it->is_eq;
-	bool is_found = false;
-	if (session_settings_next(&sid, key, is_eq, is_including) == 0)
-		is_found = true;
+	bool is_found;
+	if (!it->is_set) {
+		it->is_set = true;
+		is_found = session_settings_set_forward(&sid, key, is_eq,
+							is_including) == 0;
+	} else {
+		is_found = session_settings_next(&sid, key, is_eq,
+						 is_including) == 0;
+	}
 	it->setting_id = sid + 1;
 	if (!is_found) {
 		*result = NULL;
@@ -167,9 +241,15 @@ session_settings_iterator_prev(struct iterator *iterator, struct tuple **result)
 	int sid = it->setting_id;
 	const char *key = it->key;
 	bool is_including = it->is_including, is_eq = it->is_eq;
-	bool is_found = false;
-	if (session_settings_prev(&sid, key, is_eq, is_including) == 0)
-		is_found = true;
+	bool is_found;
+	if (!it->is_set) {
+		it->is_set = true;
+		is_found = session_settings_set_reverse(&sid, key, is_eq,
+							is_including) == 0;
+	} else {
+		is_found = session_settings_prev(&sid, key, is_eq,
+						 is_including) == 0;
+	}
 	it->setting_id = sid - 1;
 	if (!is_found) {
 		*result = NULL;
@@ -221,6 +301,7 @@ session_settings_index_create_iterator(struct index *base,
 	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->is_set = false;
 	it->format = index->format;
 	if (!iterator_type_is_reverse(type)) {
 		it->base.next = session_settings_iterator_next;
@@ -244,7 +325,7 @@ session_settings_index_get(struct index *base, const char *key,
 	key = mp_decode_str(&key, &len);
 	key = tt_cstr(key, len);
 	int sid = 0;
-	if (session_settings_next(&sid, key, true, true) != 0) {
+	if (session_settings_set_forward(&sid, key, true, true) != 0) {
 		*result = NULL;
 		return 0;
 	}
@@ -345,7 +426,7 @@ session_settings_space_execute_update(struct space *space, struct txn *txn,
 	}
 	key = mp_decode_str(&key, &key_len);
 	key = tt_cstr(key, key_len);
-	if (session_settings_next(&sid, key, true, true) != 0) {
+	if (session_settings_set_forward(&sid, key, true, true) != 0) {
 		*result = NULL;
 		return 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 ed340d053..bae77192e 100644
--- a/test/box/gh-4511-access-settings-from-any-frontend.result
+++ b/test/box/gh-4511-access-settings-from-any-frontend.result
@@ -82,6 +82,12 @@ function check_sorting(ss, ts, key)
     for _, it in pairs(iterators_list) do
         local view_space = ss:select({key}, {iterator = it})
         local test_space = ts:select({key}, {iterator = it})
+        if #view_space ~= #test_space then
+            return {
+                err = 'bad sorting', type = it, exp = test_space,
+                got = view_space
+            }
+        end
         for key, value in pairs(view_space) do
             if test_space[key].name ~= value.name then
                 return {
@@ -111,32 +117,37 @@ check_sorting(s, t, 'sql_d')
 check_sorting(s, t, 'sql_v')
  | ---
  | ...
-check_sorting(s, t, 'sql_defer_foreign_keys')
+check_sorting(s, t, 'z')
  | ---
  | ...
-
-t:drop()
+check_sorting(s, t, 'sql_parser_debuf')
+ | ---
+ | ...
+check_sorting(s, t, 'sql_parser_debuh')
  | ---
  | ...
 
--- Check get() method of session_settings space.
-s:get({'sql_defer_foreign_keys'})
+name = nil
  | ---
- | - ['sql_defer_foreign_keys', false]
  | ...
-s:get({'sql_recursive_triggers'})
+err = nil
  | ---
- | - ['sql_recursive_triggers', true]
  | ...
-s:get({'sql_reverse_unordered_selects'})
+for _, tuple in t:pairs() do                    \
+    name = tuple.name                           \
+    err = check_sorting(s, t, name)             \
+    if err then                                 \
+        break                                   \
+    end                                         \
+end
  | ---
- | - ['sql_reverse_unordered_selects', false]
  | ...
-s:get({'sql_default_engine'})
+err and {err, name}
  | ---
- | - ['sql_default_engine', 'memtx']
+ | - null
  | ...
-s:get({'abcd'})
+
+t:drop()
  | ---
  | ...
 
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 366874998..b243be15e 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
@@ -36,6 +36,12 @@ function check_sorting(ss, ts, key)
     for _, it in pairs(iterators_list) do
         local view_space = ss:select({key}, {iterator = it})
         local test_space = ts:select({key}, {iterator = it})
+        if #view_space ~= #test_space then
+            return {
+                err = 'bad sorting', type = it, exp = test_space,
+                got = view_space
+            }
+        end
         for key, value in pairs(view_space) do
             if test_space[key].name ~= value.name then
                 return {
@@ -52,17 +58,23 @@ 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')
+check_sorting(s, t, 'z')
+check_sorting(s, t, 'sql_parser_debuf')
+check_sorting(s, t, 'sql_parser_debuh')
+
+name = nil
+err = nil
+for _, tuple in t:pairs() do                    \
+    name = tuple.name                           \
+    err = check_sorting(s, t, name)             \
+    if err then                                 \
+        break                                   \
+    end                                         \
+end
+err and {err, name}
 
 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
-- 
2.21.1 (Apple Git-122.3)

Re: [Tarantool-patches] [PATCH 2/4] box: add binary search for _session_settings space

[Vladislav Shpilevoy]

Thanks for the patch!

Here is one another review fix.

================================================================================

commit 0a597ec7e4956a23d5e80420ca1d98fccab8d117
Author: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
Date:   Thu Feb 6 22:07:50 2020 +0100

    Review fix

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 f072bafae..bae77192e 100644
--- a/test/box/gh-4511-access-settings-from-any-frontend.result
+++ b/test/box/gh-4511-access-settings-from-any-frontend.result
@@ -86,7 +86,7 @@ function check_sorting(ss, ts, key)
             return {
                 err = 'bad sorting', type = it, exp = test_space,
                 got = view_space
-        }
+            }
         end
         for key, value in pairs(view_space) do
             if test_space[key].name ~= value.name then
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 40a58ad04..b243be15e 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
@@ -40,7 +40,7 @@ function check_sorting(ss, ts, key)
             return {
                 err = 'bad sorting', type = it, exp = test_space,
                 got = view_space
-        }
+            }
         end
         for key, value in pairs(view_space) do
             if test_space[key].name ~= value.name then

[Tarantool-patches] [PATCH 2/4] box: add binary search for _session_settings space

[Chris Sosnin]

I agree with your changes, but I send new version of this patch, just in case.
================================================================================

As it is mentioned in implementation, it is important
that _session_settings options are sorted by name, so
there is no need in linear lookup and we can replace it
with binary search.

Closes #4712
---
issue: https://github.com/tarantool/tarantool/issues/4711
branch: https://github.com/tarantool/tarantool/tree/ksosnin/gh-4712-search-settings

 src/box/session_settings.c                    | 97 +++++++++++++++++--
 ...1-access-settings-from-any-frontend.result | 37 ++++---
 ...access-settings-from-any-frontend.test.lua | 28 ++++--
 3 files changed, 133 insertions(+), 29 deletions(-)

diff --git a/src/box/session_settings.c b/src/box/session_settings.c
index 93d1c8e22..874fc304a 100644
--- a/src/box/session_settings.c
+++ b/src/box/session_settings.c
@@ -81,6 +81,8 @@ struct session_settings_iterator {
 	bool is_eq;
 	/** True if the iterator should include equal keys. */
 	bool is_including;
+	/** True if the iterator is pointing to an existing setting */
+	bool is_set;
 };
 
 static void
@@ -92,6 +94,72 @@ session_settings_iterator_free(struct iterator *ptr)
 	free(it);
 }
 
+static int
+session_settings_set_forward(int *sid, const char *key, bool is_eq,
+			     bool is_including)
+{
+	int low = 0, high = SESSION_SETTING_COUNT - 1;
+	if (key == NULL)
+		return 0;
+	while (low <= high) {
+		int index = (high + low) / 2;
+		const char *name = session_setting_strs[index];
+		int cmp = strcmp(name, key);
+		if (cmp == 0) {
+			if (is_including) {
+				*sid = index;
+				return 0;
+			}
+			*sid = ++index;
+			return index < SESSION_SETTING_COUNT ? 0 : -1;
+		}
+		if (cmp < 0)
+			low = index + 1;
+		else
+			high = index - 1;
+	}
+	if (is_eq) {
+		*sid = SESSION_SETTING_COUNT;
+		return -1;
+	}
+	assert(low > high);
+	*sid = low;
+	return low < SESSION_SETTING_COUNT ? 0 : -1;
+}
+
+static int
+session_settings_set_reverse(int *sid, const char *key, bool is_eq,
+			     bool is_including)
+{
+	int low = 0, high = SESSION_SETTING_COUNT - 1;
+	if (key == NULL)
+		return 0;
+	while (low <= high) {
+		int index = (high + low) / 2;
+		const char *name = session_setting_strs[index];
+		int cmp = strcmp(name, key);
+		if (cmp == 0) {
+			if (is_including) {
+				*sid = index;
+				return 0;
+			}
+			*sid = --index;
+			return index >= 0 ? 0 : -1;
+		}
+		if (cmp < 0)
+			low = index + 1;
+		else
+			high = index - 1;
+	}
+	if (is_eq) {
+		*sid = SESSION_SETTING_COUNT;
+		return -1;
+	}
+	assert(low > high);
+	*sid = high;
+	return high >= 0 ? 0 : -1;
+}
+
 static int
 session_settings_next(int *sid, const char *key, bool is_eq, bool is_including)
 {
@@ -145,9 +213,15 @@ session_settings_iterator_next(struct iterator *iterator, struct tuple **result)
 	int sid = it->setting_id;
 	const char *key = it->key;
 	bool is_including = it->is_including, is_eq = it->is_eq;
-	bool is_found = false;
-	if (session_settings_next(&sid, key, is_eq, is_including) == 0)
-		is_found = true;
+	bool is_found;
+	if (!it->is_set) {
+		it->is_set = true;
+		is_found = session_settings_set_forward(&sid, key, is_eq,
+							is_including) == 0;
+	} else {
+		is_found = session_settings_next(&sid, key, is_eq,
+						 is_including) == 0;
+	}
 	it->setting_id = sid + 1;
 	if (!is_found) {
 		*result = NULL;
@@ -167,9 +241,15 @@ session_settings_iterator_prev(struct iterator *iterator, struct tuple **result)
 	int sid = it->setting_id;
 	const char *key = it->key;
 	bool is_including = it->is_including, is_eq = it->is_eq;
-	bool is_found = false;
-	if (session_settings_prev(&sid, key, is_eq, is_including) == 0)
-		is_found = true;
+	bool is_found;
+	if (!it->is_set) {
+		it->is_set = true;
+		is_found = session_settings_set_reverse(&sid, key, is_eq,
+							is_including) == 0;
+	} else {
+		is_found = session_settings_prev(&sid, key, is_eq,
+						 is_including) == 0;
+	}
 	it->setting_id = sid - 1;
 	if (!is_found) {
 		*result = NULL;
@@ -221,6 +301,7 @@ session_settings_index_create_iterator(struct index *base,
 	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->is_set = false;
 	it->format = index->format;
 	if (!iterator_type_is_reverse(type)) {
 		it->base.next = session_settings_iterator_next;
@@ -244,7 +325,7 @@ session_settings_index_get(struct index *base, const char *key,
 	key = mp_decode_str(&key, &len);
 	key = tt_cstr(key, len);
 	int sid = 0;
-	if (session_settings_next(&sid, key, true, true) != 0) {
+	if (session_settings_set_forward(&sid, key, true, true) != 0) {
 		*result = NULL;
 		return 0;
 	}
@@ -345,7 +426,7 @@ session_settings_space_execute_update(struct space *space, struct txn *txn,
 	}
 	key = mp_decode_str(&key, &key_len);
 	key = tt_cstr(key, key_len);
-	if (session_settings_next(&sid, key, true, true) != 0) {
+	if (session_settings_set_forward(&sid, key, true, true) != 0) {
 		*result = NULL;
 		return 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 ed340d053..f072bafae 100644
--- a/test/box/gh-4511-access-settings-from-any-frontend.result
+++ b/test/box/gh-4511-access-settings-from-any-frontend.result
@@ -82,6 +82,12 @@ function check_sorting(ss, ts, key)
     for _, it in pairs(iterators_list) do
         local view_space = ss:select({key}, {iterator = it})
         local test_space = ts:select({key}, {iterator = it})
+        if #view_space ~= #test_space then
+            return {
+                err = 'bad sorting', type = it, exp = test_space,
+                got = view_space
+        }
+        end
         for key, value in pairs(view_space) do
             if test_space[key].name ~= value.name then
                 return {
@@ -111,32 +117,37 @@ check_sorting(s, t, 'sql_d')
 check_sorting(s, t, 'sql_v')
  | ---
  | ...
-check_sorting(s, t, 'sql_defer_foreign_keys')
+check_sorting(s, t, 'z')
  | ---
  | ...
-
-t:drop()
+check_sorting(s, t, 'sql_parser_debuf')
+ | ---
+ | ...
+check_sorting(s, t, 'sql_parser_debuh')
  | ---
  | ...
 
--- Check get() method of session_settings space.
-s:get({'sql_defer_foreign_keys'})
+name = nil
  | ---
- | - ['sql_defer_foreign_keys', false]
  | ...
-s:get({'sql_recursive_triggers'})
+err = nil
  | ---
- | - ['sql_recursive_triggers', true]
  | ...
-s:get({'sql_reverse_unordered_selects'})
+for _, tuple in t:pairs() do                    \
+    name = tuple.name                           \
+    err = check_sorting(s, t, name)             \
+    if err then                                 \
+        break                                   \
+    end                                         \
+end
  | ---
- | - ['sql_reverse_unordered_selects', false]
  | ...
-s:get({'sql_default_engine'})
+err and {err, name}
  | ---
- | - ['sql_default_engine', 'memtx']
+ | - null
  | ...
-s:get({'abcd'})
+
+t:drop()
  | ---
  | ...
 
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 366874998..40a58ad04 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
@@ -36,6 +36,12 @@ function check_sorting(ss, ts, key)
     for _, it in pairs(iterators_list) do
         local view_space = ss:select({key}, {iterator = it})
         local test_space = ts:select({key}, {iterator = it})
+        if #view_space ~= #test_space then
+            return {
+                err = 'bad sorting', type = it, exp = test_space,
+                got = view_space
+        }
+        end
         for key, value in pairs(view_space) do
             if test_space[key].name ~= value.name then
                 return {
@@ -52,17 +58,23 @@ 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')
+check_sorting(s, t, 'z')
+check_sorting(s, t, 'sql_parser_debuf')
+check_sorting(s, t, 'sql_parser_debuh')
+
+name = nil
+err = nil
+for _, tuple in t:pairs() do                    \
+    name = tuple.name                           \
+    err = check_sorting(s, t, name)             \
+    if err then                                 \
+        break                                   \
+    end                                         \
+end
+err and {err, name}
 
 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
-- 
2.21.1 (Apple Git-122.3)