[TINKERPOP-968] Add first class support for an optional traversal

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 3.1.0-incubating
• Fix Version/s: 3.2.0-incubating
• Component/s: process
• Assignee: pieter martin
• Reporter: pieter martin
• Created: 17/Nov/15 06:33
• Updated: 30/Mar/16 20:54
• Resolved: 30/Mar/16 20:54

Description

Both SparQL and Cypher use the "Optional" keyword to indicate an optional traversal. SQL uses the "left join".

Gremlin has no first class support for an optional traversal. It can be achieved with the choose step but it is verbose, unintuitive and not what the choose step is intended for.

The benefits of optional traversals are many. In particular it makes it trivial to load complete subgraphs/trees with one easy to read intuitive gremlin statement.