Clinker · Route and Merge, visually

RouteOrder matters, and a condition can be true, not true, or fail

- type: route
  name: classify
  input: orders
  config:
    mode: 
    conditions:
    default: standard

exclusive (default): conditions are checked top to bottom, and the first true one wins. The conditions after it are never checked, so an error further down never happens.
inclusive: the conditions are checked in order, all of them unless one fails, and the record goes down every branch whose condition is true, as a separate copy.
A condition that comes out null is "not true": the record moves on to the next one. If nothing is true, it takes the default branch.
A condition that fails (here, dividing by a quantity of 0) is neither true nor false. Under strategy: continue the record is dead-lettered and takes no branch at all, not even one already matched and not the default. Under fail_fast the run stops.

Watch order O5: its country is empty, and country != "US" is true for an empty country, because != never gives null. See where does a null go?

mode

strategy

conditions, in order (use the arrows to reorder)

default: standard

Each order

MergeJoining the branches back into one stream

A Merge brings the branches back together, here straight from the Route's ports (in a real pipeline there is usually a Transform on each branch first). It doesn't match records up: it passes along everything from every input. How the inputs are mixed depends on mode:

concat (default): all of the first input, then all of the second, in the order of inputs:. The same every run.
interleave: records pass on as they arrive from any input. Each input keeps its own order, but how the inputs mix can change from run to run.
interleave with interleave_seed: a mix that is the same every run, at the cost of reading every input into memory first. Meant for tests.

Inclusive routes make copies. A record that went down two branches comes out of the Merge twice. That is often what you want (a review queue and a flag list), but if the branches are rejoined for one output, use exclusive, or remove the copies afterwards.

All inputs must have the same columns; the Merge's columns come from its first input. A Merge never sorts: two sorted inputs concatenated are not one sorted stream. Put a sort_order on the Sink for that.

- type: merge
  name: rejoin
  inputs: 
  config:
    mode:

mode

inputs, in order (the branches from section 01)

WiringHow the next node picks a branch

Port syntax

A node reads one branch with input: classify.big, and the default branch the same way: input: classify.standard. A Merge lists branches in inputs:.

The name shortcut

A node whose own name matches a branch can write input: classify, and it receives that branch. A Sink named big reading classify gets the big branch.

One branch, two readers

Several nodes can read the same branch; each gets every record on it.

Branch names

Use names that differ from each other and from default. Today a default with the same name as a condition is folded into that condition's branch without an error, so its records can't be told apart.