Table(cast(xyz as abc) ?

Question

In the function below can any one put some light on "TABLE(CAST( v_id_tab AS fe_id_tab)) pid" & pid.COLUMN_VALUE
FUNCTION get_advisees_list
i_agent_rel_id IN fe_relation.relation_id%TYPE,
i_get_clients IN SMALLINT,
i_get_prospects IN SMALLINT,
i_branch_code     IN fm_plan.branch_code_id%TYPE,      
i_rep_code          IN fm_plan.rep_code_id%TYPE
RETURN SYS_REFCURSOR
IS
v_rc SYS_REFCURSOR;
v_id_tab fe_id_tab;
BEGIN
/** get all advisees id up front **/
v_id_tab := advisees_ids(i_agent_rel_id);
OPEN v_rc FOR
SELECT /*+ CARDINALITY(pid 50) INDEX (per person_pk) */
per.person_id,
1 is_client,
0 is_prospect,
per.username,
per.broker_tag,
per.first_nm,
per.last_nm
FROM TABLE(CAST( v_id_tab AS fe_id_tab)) pid
JOIN FE_PERSON per
ON per.person_id = pid.COLUMN_VALUE
AND per.is_active = 1
JOIN FE_RELATION clnt_rel
ON clnt_rel.abs_relation_cd = Fec.rel_client_cd
AND clnt_rel.entity_2_id = per.person_id
AND clnt_rel.is_active = 1
WHERE i_get_clients = 1
UNION
SELECT /*+ CARDINALITY(pid 50) INDEX ( per person_pk) */
per.person_id,
0 is_client,
1 is_prospect,
per.username,
per.broker_tag,
per.first_nm,
per.last_nm
FROM TABLE(CAST( v_id_tab AS fe_id_tab)) pid
JOIN FE_PERSON per
ON per.person_id = pid.column_value
JOIN FE_RELATION clnt_rel
ON clnt_rel.abs_relation_cd = Fec.rel_prospect_cd
AND clnt_rel.entity_2_id = per.person_id
AND clnt_rel.is_active = 1
WHERE i_get_prospects = 1
ORDER BY 7,6;
RETURN v_rc;
END get_advisees_list;

Answer 1

You mean what does it do?
The local variable v_id_tab is a collection type (similar to an array) of type fe_id_tab (created via the CREATE TYPE syntax and visible via USER_COLL_TYPES).
The TABLE (CAST ()) syntax allows this collection to be queried in SQL as if it were a relational table.
The COLUMN_VALUE syntax is used as a default column name for the collection type when the collection is of type scalar (NUMBER / DATE / VARCHAR2 etc.) rather than of object type.
Also the /*+ CARDINALITY */ hint is suggesting to the optimizer that the collection should be expected to contain 50 rows.