[TINKERPOP-1741] GroupStep's on-the-fly reducer is a bit screwy

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Invalid
• Affects Version/s: 3.2.5
• Component/s: process
• Assignee: Marko A. Rodriguez
• Reporter: Daniel Kuppitz
• Created: 07/Aug/17 15:03
• Updated: 07/Aug/17 17:26
• Resolved: 07/Aug/17 17:26

Description

Without dedup():

gremlin> g.V().both().has("age").group("a").by("age").by(values("name").fold()).barrier().select("a").limit(1)
==>[32:[josh,josh,josh],35:[peter],27:[vadas],29:[marko,marko,marko]]

With dedup():

gremlin> g.V().both().has("age").group("a").by("age").by(values("name").dedup().fold()).barrier().select("a").limit(1)
==>[32:[josh:josh],35:[peter:peter],27:[vadas:vadas],29:[marko:marko]]

Why do the values end up being maps? That's pretty unexpected.

As a workaround we can do this:

gremlin> g.withSideEffect("a", [:].withDefault {[] as Set}).V().both().has("age").group("a").by("age").by(values("name").fold()).barrier().select("a").limit(1)
==>[27:[vadas],32:[josh],29:[marko],35:[peter]]

Also note, that cap() behaves correctly, even though we're using dedup():

gremlin> g.V().both().has("age").group("a").by("age").by(values("name").dedup().fold()).barrier().cap("a")
==>[32:[josh],35:[peter],27:[vadas],29:[marko]]