The UnNest operator unpacks incoming tuple with a multi value attribute (e.g. a list) to create multiple tuples each containg one value from that attribute.
attribute:The attribute that should be unpack.
useInnerMetadata: Boolean; optional; default is false. Requires the attribute to unpack to be a list of tuples, each with meta data. If set to true and if the meta data schema of the tuples to be unpacked matches the meta data schema of the outer tuple, the meta data from the unpacked tuple is set as meta data of the output of the unnest operator.