13.47 PIPELINED Clause

Instructs the database to return the results of a table function iteratively.

Use only with a table function, to specify that it is pipelined. A pipelined table function returns a row to its invoker immediately after processing that row and continues to process rows. To return a row (but not control) to the invoker, the function uses the "PIPE ROW Statement".

A table function returns a collection type (a nested table or varray). You query table functions by using the TABLE keyword before the function name in the FROM clause of the query. For example:

SELECT * FROM TABLE(function_name(...))

the database then returns rows as they are produced by the function.






PIPELINED can appear only once in the function.

  • If you specify the keyword PIPELINED alone (PIPELINED IS ...), then the PL/SQL function body must use the PIPE keyword. This keyword instructs the database to return single elements of the collection out of the function, instead of returning the whole collection as a single value.

  • You can specify the PIPELINED USING implementation_type clause to predefine an interface containing the start, fetch, and close operations. The implementation type must implement the ODCITable interface and must exist at the time the table function is created. This clause is useful for table functions implemented in external languages such as C++ and Java.

    If the return type of the function is ANYDATASET, then you must also define a describe method (ODCITableDescribe) as part of the implementation type of the function.

Restriction on PIPELINED

You cannot specify PIPELINED for a nested function.


You cannot run a pipelined table function over a database link. The reason is that the return type of a pipelined table function is a SQL user-defined type, which can be used only in a single database (as explained in Oracle Database Object-Relational Developer's Guide). Although the return type of a pipelined table function might appear to be a PL/SQL type, the database actually converts that PL/SQL type to a corresponding SQL user-defined type.