gistfile1.htm

IDT1 = ID of Thread 1, T1 = Thread 1, RT1 = Reply 1 to Thread 1, RT2 = Reply 2 to Thread 1, RT3 = Reply 3 to Thread 1, IDR1 = ID of Reply 1, IDR2 = ID of Reply 2, IDR3 = ID of Reply 3

Remember that the inputs to a reduce function are like so:

Parameter 1: key : Array whose elements are of the form [key, id] where key is the key emitted by the map function and id is the ID of the document from which the key is generated
Parameter 2: values : Array of values returned by previous calls to the reduce function (OR) array of values emitted for respective elements in keys
Parameter 3: rereduce : Can be either true or false

Scenario 1:

Reduce function called like this:

reduce([ [IDT1, IDT1], [IDT1, IDR1], [IDT1, IDR2], [IDT1, IDR3] ], [T1, RT1, RT2, RT3, RT4], false); -> Emits final value


Scenario 2:

Reduce function called multiple times like this:

reduce([IDT1, IDT1], [T1], false) -> Emits Intermediate Value O1 (called with rereduce = false)
reduce([IDT1, IDR1], [RT1], false) -> Emits Intermediate Value O2 (called with rereduce = false)
reduce([IDT1, IDR2], [RT2], false) -> Emits Intermediate Value O3 (called with rereduce = false)
reduce([IDT1, IDR3], [RT3], false) -> Emits Intermediate Value O4 (called with rereduce = false)

and finally

reduce(null, [O1, O2, O3, O4], true) -> Emits final value (called with rereduce = true)