testing_project/Documentation: dev_guide/internals/iproto/sql

Zen

	English	Russian	Actions
	0x0d
	Prepare an SQL statement (:ref:`box.prepare() <box-sql_box_prepare>`)
	IPROTO_EXECUTE
	Code: 0x0b.
	The body is a 3-item map:
	Use IPROTO_STMT_ID (0x43) and statement-id (MP_INT) if executing a prepared statement. Use IPROTO_SQL_TEXT (0x40) and statement-text (MP_STR) if executing an SQL string.
	IPROTO_SQL_BIND (0x41) corresponds to the array of parameter values to match ? placeholders or :name placeholders.
	IPROTO_OPTIONS (0x2b) corresponds to the array of options. It is usually empty.
	Example 1
	Suppose we prepare a statement with two ? placeholders, and execute with two parameters, thus:
	n = conn:prepare([[VALUES (?, ?);]]) conn:execute(n.stmt_id, {1,'a'})
	Then the body will look like this:
	The :ref:`Understanding binary protocol <box_protocol-illustration>` tutorial shows actual byte codes of the IPROTO_EXECUTE message.
	To call a prepared statement with named parameters from a connector pass the parameters within an array of maps. A client should wrap each element into a map, where the key holds a name of the parameter (with a colon) and the value holds an actual value. So, to bind foo and bar to 42 and 43, a client should send ``IPROTO_SQL_TEXT: <...>, IPROTO_SQL_BIND: [{"foo": 42}, {"bar": 43}]``.
	If a statement has both named and non-named parameters, wrap only named ones into a map. The rest of the parameters are positional and will be substituted in order.
	Example 2
	Let's ask for full metadata and then select the two rows from a table named t1 that has columns named DD and Д:
	conn.space._session_settings:update('sql_full_metadata', {{'=', 'value', true}}) conn:prepare([[SELECT dd, дд AS д FROM t1;]])
	In the iproto request, there would be no IPROTO_DATA and there would be two additional items:
	``34 00 = IPROTO_BIND_COUNT and MP_UINT = 0`` (there are no parameters to bind).
	``33 90 = IPROTO_BIND_METADATA and MP_ARRAY, size 0`` (there are no parameters to bind).
	Here is what the request body looks like:
	IPROTO_PREPARE
	Code: 0x0d.
	The body is a 1-item map:
	The IPROTO_PREPARE map item is the same as the first item of the :ref:`IPROTO_EXECUTE <box_protocol-execute>` body for an SQL string.
	Responses for SQL
	After the :ref:`header <box_protocol-header>`, for a response to an SQL statement, there will be a body that is slightly different from the body for non-SQL requests/responses.
	Responses to SELECT, VALUES, or PRAGMA
	If the SQL statement is SELECT or VALUES or PRAGMA, the response contains:
	Example