coalesce
Return a value based on the first traversal that has an element.
Synopsis
coalesce(traversal,traversal,...)Description
The coalesce() step evaluates the provided traversals in order and returns the first traversal that emits at least one element.
Examples
Create a list of each person and their mean average of stars given for recipe reviews, using coalesce() to either print the mean or print a constant zero value if no reviews are found:
"g.V().hasLabel('person').as('person','starCount').
select('person','starCount').
by('name').
by(coalesce(outE('reviewed').values('stars'),constant(0)).mean()).
order().by(select('starCount'), decr)"