[TINKERPOP-2627] Use of union() in second by() to group()

• Type: Bug
• Status: Open
• Priority: Minor
• Resolution: Unresolved
• Affects Version/s: 3.4.12
• Component/s: process
• Assignee: Unassigned
• Reporter: Stephen Mallette
• Created: 14/Oct/21 19:33
• Updated: 18/Nov/21 11:38

Description

Using air routes dataset, you get some odd output if you `union(...).fold()` in the second `by()` and if the children to `union()` are reducing steps:

gremlin> g.V().hasLabel('airport').has('country','TZ').
......1>   group().
......2>     by('country').
......3>     by(union(values('elev').min(), values('elev').max()).fold()).
......4>   unfold()
==>TZ=[3745, 3745, 2932, 2932, 3763, 3763, 371, 371, 5600, 5600, 4550, 4550, 182, 182, 54, 54]

I was able to workaround it with:

gremlin> g.V().hasLabel('airport').has('country','TZ').
......1>   group().
......2>     by('country').
......3>     by(values('elev').fold().local(union(min(local),max(local))).fold()).
......4>   unfold()
==>TZ=[54, 5600]