optional
Returns an optional result if the specified traversal yields a result; otherwise, returns the calling element.
Synopsis
optional(traversal_fragment)| Syntax conventions | Description |
|---|---|
| Lowercase and uppercase | Literal keyword. Includes (). |
Italics |
Variable value. Replace with a user-defined value. |
[] |
Optional. Square brackets ( [] ) surround
optional command arguments. Do not type the square brackets. |
{} |
Group. Braces ( {} ) identify a group to choose
from. Do not type the braces. |
| |
Or. A vertical bar ( | ) separates alternative
elements. Type any one of the elements. Do not type the vertical
bar. |
... |
Repeatable. An ellipsis ( ... ) indicates that
you can repeat the syntax element as often as required. |
Description
The optional() step is a branch/flatMap step that will either
return the result of the specified traversal if it yields a result, or the return of the
calling element.
Examples
Returns the friends of John Doe, since he has
friends:
g.V().has('person', 'name', 'John Doe').optional(out('knows'))Returns Julia Child, since she has no linked
friends:
g.V().has('person', 'name', 'Julia Child').optional(out('knows'))