Window Iterators

Window iterators are a means of explicitly iterating over all of the records stored in a window. It is usually more convenient, and safer, to use the for loop mechanism if the goal is to iterate over the data once, but iterators provide extra flexibility.

Functions for Iterators

Each block of code has implicit variables for windows and window iterators. If an input window is named Stream1, there are variables Stream1_stream and Stream1_iterator.

Those variables can be used in conjunction with the following functions.

deleteIterator – Releases the resources associated with an iterator.
Syntax: deleteIterator(iterator)

Type: The argument must be an iterator expression. The function returns a null value.

Example: deleteIterator(input_iterator)

Note: Iterators are not implicitly deleted. If you don't delete them explicitly, all further updates to the stream may be blocked.
getIterator – Get an iterator for a window.
Syntax: getIterator(windowName)

Type: The argument must be a window expression. The function returns an iterator.

Example: getIterator(input_window)
getNext – Returns the next record in the iterator, or null if there are no more records.
Syntax: getNext(iterator)

Type: The first argument must be an iterator expression. The function returns a record, or "null" if there is no more data in the iterator.

Example: getNext(input_iterator)
resetIterator – Resets the iterator to the beginning.
Syntax: resetIterator(iterator)

Type: The argument must be an iterator expression. The function returns an iterator.

Example: resetIterator(input_iterator)
setRange – Sets a range of columns to search for. Subsequent getNext calls return only those records whose columns match the given values.
Syntax: setRange(iterator fieldName... expr...)

Type: The first argument must be an iterator expression; the next arguments must be the names of fields within the record; the final arguments must be expressions. The function returns an iterator.

Example: setRange(input_iterator,Currency,Rate,'EUR',9.888)
setSearch – Sets values of columns to search for. Subsequent getNext calls return only those records whose columns match the given values.
Syntax: setSearch( iterator number... expr...)

Type: The first argument must be an iterator expression; the next arguments must be column numbers (starting from 0) in the record; the final arguments must be expressions. The function returns an iterator.

Example: setSearch(input_iterator,0,2,'EUR',9.888)

Note: The setSearch function has been deprecated because it requires a specific layout of fields. It has been retained for backwards compatibility with existing projects. When developing new projects, use the setRange function instead.