Cherry pick a set of messages from a batch by their index. Indexes larger than the number of messages are simply ignored.
The selected parts are added to the new message batch in the same order as the selection array. E.g. with 'parts' set to [ 2, 0, 1 ] and the message parts [ '0', '1', '2', '3' ], the output will be [ '2', '0', '1' ].
If none of the selected parts exist in the input batch (resulting in an empty output message) the batch is dropped entirely.
Message indexes can be negative, and if so the part will be selected from the end counting backwards starting from -1. E.g. if index = -1 then the selected part will be the last part of the message, if index = -2 then the part before the last element with be selected, and so on.
The functionality of this processor depends on being applied across messages that are batched. You can find out more about batching in this doc.
array An optional array of message indexes of a batch that the processor should apply to.
If left empty all messages are processed. This field is only applicable when
batching messages at the input level.
Indexes can be negative, and if so the part will be selected from the end counting backwards starting from -1.