mysql_stmt_attr_set

mysql_stmt_attr_set configures a prepared statement attribute on a Connector/C statement handle; supported attributes include cursor type, prefetch rows, and bulk-insert array size.

Syntax

my_bool mysql_stmt_attr_set(MYSQL_STMT * stmt,
                            enum enum_stmt_attr_type,
                            const void * attr);

Parameters

Parameter	Description
stmt	A statement handle, which was previously allocated by mysql_stmt_init().
enum_stmt_attr_type	The attribute that can be configured. See Attribute Types.
attr	The value to assign to the attribute

Description

Used to modify the behavior of a prepared statement. This function may be called multiple times to set several attributes. Returns zero on success, non-zero on failure.

Attribute Types

The enum_stmt_attr_type attribute can have one of the following values:

• STMT_ATTR_UPDATE_MAX_LENGTH If set to 1, mysql_stmt_store_result() will update the max_length value of MYSQL_FIELD structures.

my_bool update= 1;
rc= mysql_stmt_attr_set(stmt, STMT_ATTR_UPDATE_MAX_LENGTH, &update);

• STMT_ATTR_CURSOR_TYPE: cursor type when mysql_stmt_execute() is invoked. Possible values are CURSOR_TYPE_READ_ONLY or default value CURSOR_TYPE_NO_CURSOR.

unsigned long cursor_type= CURSOR_TYPE_READ_ONLY;
rc= mysql_stmt_attr_set(stmt, STMT_ATTR_CURSOR_TYPE, &cursor_type);

• STMT_ATTR_PREFETCH_ROWS: number of rows which will be prefetched. The default value is 1.

unsigned long rows=4;
rc= mysql_stmt_attr_set(stmt, STMT_ATTR_PREFETCH_ROWS, &rows);

• STMT_ATTR_PREBIND_PARAMS: number of parameter markers when using mariadb_stmt_execute_direct(). If the statement handle is reused it will be reset automatically to the state after mysql_stmt_init(). This option was added in Connector/C 3.0

unsigned int params= 5;
rc= mysql_stmt_attr_set(stmt, STMT_ATTR_PREBIND_PARAMS, ¶ms);

• STMT_ATTR_ARRAY_SIZE: number of array elements. This option was added in Connector/C 3.0 and requires MariaDB 10.2 or later

unsigned int array_size= 5;
rc= mysql_stmt_attr_set(stmt, STMT_ATTR_ARRAY_SIZE, &array_size);

• STMT_ATTR_ROW_SIZE: specifies size of a structure for row wise binding. This length must include space for all of the bound parameters and any padding of the structure or buffer to ensure that when the address of a bound parameter is incremented with the specified length, the result will point to the beginning of the same parameter in the next set of parameters. When using the sizeof operator in ANSI C, this behavior is guaranteed. If the value is zero column-wise binding will be used (default). This option was added in Connector/C 3.0 and requires MariaDB 10.2 or later

size_t row_size= sizeof(struct st_customer);
rc= mysql_stmt_attr_set(stmt, STMT_ATTR_ROW_SIZE, &array_size);

• If you use the MYSQL_STMT_ATTR_CURSOR_TYPE option with MYSQL_CURSOR_TYPE_READ_ONLY, a cursor is opened for the statement when you invoke mysql_stmt_execute(). If there is already an open cursor from a previous mysql_stmt_execute() call, it closes the cursor before opening a new one. mysql_stmt_reset() also closes any open cursor before preparing the statement for re-execution.

• If you open a cursor for a prepared statement, it is unnecessary to call mysql_stmt_store_result().

• mysql_stmt_free_result() closes any open cursor.

See Also

• mariadb_stmt_execute_direct()

• mysql_stmt_attr_get()