Replaces some tuple value with another. The replacement value can be either a given value or the
value of another field in the tuple. The expression for a replace operation can be of multiple forms:
replace(fieldA, 0, withValue=100) // for fieldA if equals 0 then set to 100
replace(fieldA, null, withValue=0) // for fieldA if null then set to 0
replace(fieldA, null, withField=fieldB) // for fieldA if null then set to the value of fieldB (if fieldB is null then fieldA will end up as null)
replace(fieldA, 0, withField=fieldB) // for fieldA if 0 then set to the value of fieldB (if fieldB is 0 then fieldA will end up as 0)
replace(fieldA, "Izzy and Kayden", withValue="my kids")
You can also construct these without the field name in the expression but that does require that you provide the field name during construction.
This is most useful during metric calculation because when calculating a metric you have already provided a field name in the metric so there
is no reason to have to provide the field name again in the operation
sum(fieldA, replace(null, withValue=0)) // performs the replacement on fieldA
Equality is determined by the standard type .equals() functions.