From the node help
Sequence rules can be used on message sequences, such as those generated by the Split node
(@dceejay please correct me if I'm wrong),
- Sequence Rules are based on msg.parts.count and msg.parts.index - if either of them are missing from the msg, those rules will not do anything.
Property option plays no part in the Sequence rules. You can leave that option blank and while it will produce a warning that the node is not properly configured, it will still work
- HEAD - will return the first thru Nth msgs where N is the value in the head option.
- INDEX BETWEEN will return the msgs in the sequence
based on msg.index - remember the first msg is index 0, the second msg is index 1, etc), between the two values specified
- TAIL - will return the Nth last msgs in the sequence where N is the value in the tail option. If you set 'Tail' to 1, it will return the lsat msg in the sequence. If you set it to 3, it will return the last three msgs in the sequence.
NOTE: It is possible - with 'check all rules' selected, to get multiple copies of the same message depending on your settings. For example, say you start with a msg.payload of 'this is a test' and you set 'Head' to 1, 'Index between' to 1 and 2 and 'Tail' to 2, you will get 'this', 'is', 'a', 'a', 'test'