The mi_collection_fetch() function

Syntax

mi_integer mi_collection_fetch(conn, coll_desc, action, jump, value_buf,
   value_len)
   MI_CONNECTION *conn;
   MI_COLL_DESC *coll_desc;
   MI_CURSOR_ACTION action;
   mi_integer jump;
   MI_DATUM *value_buf;
   mi_integer *value_len;

conn

A pointer to a connection descriptor established by a previous call to mi_open(), mi_server_connect(), or mi_server_reconnect().

coll_desc

A pointer to the collection descriptor for the collection from which to fetch.

action

This value determines the orientation of the fetch. When a collection opens, elements are available in a cursor. The current cursor position is before the first element. Possible action values are:

MI_CURSOR_NEXT

Fetches the next element after the current cursor position.

MI_CURSOR_PRIOR

Fetches the element before the current cursor position.

MI_CURSOR_FIRST

Fetches the first element.

MI_CURSOR_LAST

Fetches the last element.

MI_CURSOR_ABSOLUTE

Moves jump elements from the beginning of the cursor and fetches the element at the new cursor position.

MI_CURSOR_RELATIVE

Moves jump elements from the current position and fetches the element at this new cursor position.

MI_CURSOR_CURRENT

Fetches the element at the current cursor position.

jump

is the absolute or relative offset of the fetch for list collections only. If action is not MI_CURSOR_ABSOLUTE or MI_CURSOR_RELATIVE when jump is specified, the function raises an exception and returns MI_NULL_VALUE.

For absolute positioning, a jump value of 1 is the first element.

value_buf

A pointer to the MI_DATUM structure that contains the collection element. The mi_collection_fetch() function allocates the MI_DATUM structure. You do not need to supply the buffer to hold the returned value.

value_len

A pointer to the length of the fetched collection element in the value_buf argument.

Usage

The mi_collection_fetch() function fetches the element that action specifies from the open collection that coll_desc references. This function retrieves the specified element from the collection cursor associated with coll_desc and puts this element into the MI_DATUM structure that value_buf references.

For descriptions of collections and of MI_DATUM values, see the Informix® DataBlade® API Programmer's Guide.

If you need to save the data for later use, you must create your own copy of the data that value_buf references. For example, if the collection element is a character string, the data in value_buf is a pointer to an mi_lvarchar structure. To save the data in the mi_lvarchar structure, you can copy it with the mi_var_copy() function.

Return values

MI_NULL_VALUE

The returned data is NULL.

MI_END_OF_DATA

No more data remains to be fetched or the jump position is past the last element.

MI_ERROR

The connection handle is invalid.

MI_ROW_VALUE

The fetched element is a row.

MI_COLLECTION_VALUE

The fetched element is a collection.

MI_NORMAL_VALUE

Execution of the function was successful.

The mi_collection_fetch() function raises an exception for a bad argument, such as a null connection.