Behaviour of Coalesce Step

[Udit Sharma]

Sample Graph

g=TinkerGraph.open().traversal()

g.addV().property('type','student').property('id','student1').as('s1').

addV().property('type','course').property('id','course1').as('c1').

addV().property('type','teacher').property('id','teacher1').as('t1').

addV().property('type','teacher').property('id','teacher2').as('t2').

addV().property('type','department').property('id','department1').as('d1').

addE('worksFor').from('t1').to('d1').

addE('worksFor').from('t2').to('d1').

addE('headOf').from('t1').to('d1').

addE('teacherOf').from('t1').to('c1').

addE('takesCourse').from('s1').to('c1').

addE('advisor').from('s1').to('t1')

Query 1:

g.V().match(__.as('temp').has('id',"department1"),

__.as('temp').in('worksFor','headOf').as('X')).match(

__.as('X').out('teacherOf').as('Z'),

__.as('Z').in('takesCourse').as('Y'),

__.as('Y').out('advisor').as('X'))

Output:

==>[X:v[6],Y:v[0],Z:v[3]]

==>[X:v[6],Y:v[0],Z:v[3]]

Query 2:

g.V().match(__.as('temp').has('id',"department1"),

__.as('temp').in('worksFor','headOf').as('X')).coalesce(match(

__.as('X').out('teacherOf').as('Z'),

__.as('Z').in('takesCourse').as('Y'),

__.as('Y').out('advisor').as('X')))

Output

==>[X:v[6],Y:v[0],Z:v[3]]

==>[X:v[6],Y:v[0],Z:v[3]]

==>[X:v[6],Y:v[0],Z:v[3]]

==>[X:v[6],Y:v[0],Z:v[3]]

Why output printed by Query 2 is different from the output generated by Query 1? Shouldn't coalesce step behave as it is not present if we pass only a single argument to it?