org.apache.beam.sdk.transforms

Annotation Type DoFn.GetSize

@Documented
 @Retention(value=RUNTIME)
 @Target(value=METHOD)
 @Experimental(value=SPLITTABLE_DO_FN)
public static @interface DoFn.GetSize

Annotation for the method that returns the corresponding size for an element and restriction pair.

Signature: double getSize(InputT element, RestrictionT restriction);

Returns a double representing the size of the element and restriction.

A representation for the amount of known work represented as a size. Size representations should preferably represent a linear space and be comparable within the same partition (see DoFn.GetPartition for details on partition identifiers}).

Splittable DoFns should only provide this method if the default implementation within the RestrictionTracker is an inaccurate representation of known work.

It is up to each splittable to convert between their natural representation of outstanding work and this representation. For example:

• Block based file source (e.g. Avro): From the end of the current block, the remaining number of bytes to the end of the restriction.
• Pull based queue based source (e.g. Pubsub): The local/global size available in number of messages or number of message bytes that have not been processed.
• Key range based source (e.g. Shuffle, Bigtable, ...): Scale the start key to be one and end key to be zero and interpolate the position of the next splittable key as the size. If information about the probability density function or cumulative distribution function is available, size interpolation can be improved. Alternatively, if the number of encoded bytes for the keys and values is known for the key range, the number of remaining bytes can be used.