Query Operators

FuncADL is inspired by functional languages and C#’s LINQ. If you would like to learn more about LINQ, you can refer to the following resources:

See Wikipedia

FuncADL Query Operators

In order to use FuncADL it is helpful to understand the query operators that are available.

SelectMany

Given that the current stream’s object type is an array or other iterable, this both transforms and flattens it by returning the contained items one by one.

Arguments:
    func:   The function that should be applied to each of this stream's objects, returning a transformed object. Each item of the iterable is now the stream of objects.

Returns:
    A new ObjectStream of the type of the elements.

Notes:
    - The function can be a `lambda`, the name of a one-line function, a string that
        contains a lambda definition, or a python `ast` of type `ast.Lambda`.

Select

Apply a transformation function to each object in the stream, yielding a new type of object. There is a one-to-one correspondence between the input objects and output objects.

Arguments:
    f: selection function (lambda)

Returns:
    A new ObjectStream of the transformed elements.

Notes:
    - The function can be a `lambda`, the name of a one-line function, a string that
    contains a lambda definition, or a python `ast` of type `ast.Lambda`.

Where

Filter the object stream, allowing only items for which filter evaluates as true through.

Arguments:
    filter: A filter lambda that returns True/False.

Returns:
    A new ObjectStream that contains only elements that pass the filter function

Notes:
    - The function can be a `lambda`, the name of a one-line function, a string that
    contains a lambda definition, or a python `ast` of type `ast.Lambda`.

Advanced Query Operators

MetaData

Add metadata to the current object stream. The metadata is an arbitrary set of string key-value pairs. The backend must be able to properly interpret the metadata.

Returns:
    ObjectStream: A new stream, of the same type and contents, but with metadata added.

QMetaData

Add query metadata to the current object stream.

• Metadata is never transmitted to any back end

• Metadata is per-query, not per sample.

Warnings are issued if metadata is overwriting metadata.

Args:
    metadata (Dict[str, Any]): Metadata to be used later

Returns:
    ObjectStream[T]: The object stream, with metadata attached