Recursive relationship functions

Function	Description
`NODES`	returns all nodes from a path
`RELS`	returns all relationships from a path
`PROPERTIES`	return a given property from nodes or relationships
`IS_TRAIL`	check if a path contains repeated relationships
`IS_ACYCLIC`	check if a path contains repeated nodes
`LENGTH`	returns the number of relationships (path length) in a path
`COST`	returns the cost of a weighted path

NODES

Returns all nodes from a path.

Input type	Output type
`RECURSIVE_REL`	`LIST[NODE]`

MATCH p = (a:User)-[:Follows*1..2]->(:User)
WHERE a.name = 'Adam'
RETURN nodes(p);

------------------------------------------------------------------------------------
| NODES(p)                                                                         |
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| [{_ID: 0:0, _LABEL: User, name: Adam, age: 30},{_ID: 0:1, _LABEL: User, name:... |
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| [{_ID: 0:0, _LABEL: User, name: Adam, age: 30},{_ID: 0:1, _LABEL: User, name:... |
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| [{_ID: 0:0, _LABEL: User, name: Adam, age: 30},{_ID: 0:2, _LABEL: User, name:... |
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| [{_ID: 0:0, _LABEL: User, name: Adam, age: 30},{_ID: 0:2, _LABEL: User, name:... |
------------------------------------------------------------------------------------

RELS

Returns all relationships from a path.

Input type	Output type
`RECURSIVE_REL`	`LIST[REL]`

MATCH p = (a:User)-[:Follows*1..2]->(:User)
WHERE a.name = 'Adam'
RETURN rels(p);

------------------------------------------------------------------------------------
| RELS(p)                                                                          |
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| [(0:0)-{_LABEL: Follows, _ID: 2:0, since: 2020}->(0:1)]                          |
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| [(0:0)-{_LABEL: Follows, _ID: 2:0, since: 2020}->(0:1),(0:1)-{_LABEL: Follows... |
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| [(0:0)-{_LABEL: Follows, _ID: 2:1, since: 2020}->(0:2)]                          |
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| [(0:0)-{_LABEL: Follows, _ID: 2:1, since: 2020}->(0:2),(0:2)-{_LABEL: Follows... |
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PROPERTIES

Return a given property from nodes or relationships.

Input type	Output type
`LIST[NODE/REL]`, `STRING`	`LIST[ANY]`

MATCH p = (a:User)-[:Follows*1..2]->(:User)
WHERE a.name = 'Adam'
RETURN properties(nodes(p), 'name') AS name, properties(rels(p), 'since') AS since;

--------------------------------------
| name                 | since       |
--------------------------------------
| [Adam,Karissa]       | [2020]      |
--------------------------------------
| [Adam,Karissa,Zhang] | [2020,2021] |
--------------------------------------
| [Adam,Zhang]         | [2020]      |
--------------------------------------
| [Adam,Zhang,Noura]   | [2020,2022] |
--------------------------------------

IS_TRAIL

Check if a path contains repeated relationships.

Input type	Output type
`RECURSIVE_REL`	`BOOLEAN`

MATCH p = (a:User)-[:Follows*2..2]-(b:User)
WHERE a.name='Adam'
RETURN properties(rels(p), '_id'), is_trail(p);

Output

-----------------------------------------
| PROPERTIES(RELS(p),_id) | IS_TRAIL(p) |
-----------------------------------------
| [2:1,2:1]               | False       |
-----------------------------------------
| [2:0,2:0]               | False       |
-----------------------------------------
| [2:1,2:2]               | True        |
-----------------------------------------
| [2:0,2:2]               | True        |
-----------------------------------------
| [2:1,2:3]               | True        |
-----------------------------------------

IS_ACYCLIC

Check if a path contains repeated nodes.

Input type	Output type
`RECURSIVE_REL`	`BOOLEAN`

MATCH p = (a:User)-[:Follows*2..2]-(b:User)
WHERE a.name='Adam'
RETURN properties(nodes(p), 'name'), is_acyclic(p);

---------------------------------------------
| PROPERTIES(NODES(p),name) | IS_ACYCLIC(p) |
---------------------------------------------
| [Adam,Zhang,Adam]         | False         |
---------------------------------------------
| [Adam,Karissa,Adam]       | False         |
---------------------------------------------
| [Adam,Zhang,Karissa]      | True          |
---------------------------------------------
| [Adam,Karissa,Zhang]      | True          |
---------------------------------------------
| [Adam,Zhang,Noura]        | True          |
---------------------------------------------

LENGTH

Return the number of relationships (path length) in a path.

MATCH p = (a:User)-[f:Follows*1..2]->(b:User)
RETURN LENGTH(p);

----------------
| LENGTH(p)    |
----------------
| 1            |
----------------
| 2            |
----------------
| 1            |
----------------
| 2            |
----------------

The LENGTH function when applied to a recursive relationship is equivalent to SIZE(rels(p)).

COST

Return the cost of a weighted path. This function only works for WSHORTEST and ALL WSHORTEST.

Input type	Output type
`RECURSIVE_REL`	`DOUBLE`

Example

MATCH (a:User)-[e:Follows]->(b:User) RETURN a.name, e.*, b.name;
┌─────────┬─────────┬───────────┬─────────┐
│ a.name  │ e.since │ e.score   │ b.name  │
│ STRING  │ INT64   │ DOUBLE    │ STRING  │
├─────────┼─────────┼───────────┼─────────┤
│ Adam    │ 2020    │ 5.000000  │ Karissa │
│ Adam    │ 2020    │ 20.000000 │ Zhang   │
│ Karissa │ 2021    │ 6.000000  │ Zhang   │
│ Zhang   │ 2022    │ 22.000000 │ Noura   │
└─────────┴─────────┴───────────┴─────────┘
MATCH p=(a:User)-[e:Follows* WSHORTEST(score)]->(b:User)
WHERE a.name='Adam' RETURN properties(nodes(p), 'name'), cost(e);
┌────────────────────────────┬───────────┐
│ PROPERTIES(NODES(p),name)  │ e_cost    │
│ STRING[]                   │ DOUBLE    │
├────────────────────────────┼───────────┤
│ [Adam,Karissa,Zhang,Noura] │ 33.000000 │
│ [Adam,Karissa,Zhang]       │ 11.000000 │
│ [Adam,Karissa]             │ 5.000000  │
└────────────────────────────┴───────────┘