jrgemignani commented on issue #330:
URL: https://github.com/apache/age/issues/330#issuecomment-1282936299
The following -
`CREATE (a:A {foo:1})-[:incs]->(:C), (a)-[:incs]->(:C) RETURN a`
creates 2 **distinct** paths joined at node **a**. So, 3 **distinct** nodes
and 2 **distinct** edges.
```
psql-11.5-5432-pgsql=# SELECT * FROM cypher('test', $$ MATCH (u)-[e]->(v)
RETURN e $$) AS (e agtype);
e
----------------------------------------------------------------------------------------------------------------------------
{"id": 1125899906842658, "label": "incs", "end_id": 1407374883553314,
"start_id": 844424930132002, "properties": {}}::edge
{"id": 1125899906842659, "label": "incs", "end_id": 1407374883553315,
"start_id": 844424930132002, "properties": {}}::edge
(2 rows)
```
`()<-[]-(a)-[]->()`
The following -
`MATCH (a:A) WHERE exists(a.foo) WITH a OPTIONAL MATCH (a)-[:incs]->(c)
RETURN c`
matches those 2 **distinct** paths joined at **a** and returns **c** - each
paths' endpoint.
The following -
`MATCH (a:A) WHERE exists(a.foo) WITH a OPTIONAL MATCH
(a)-[:incs]->(c)-[d:incs]-() WITH a,c,COUNT(d) AS deps WHERE deps=1 RETURN
c,deps`
doesn't do what you may think it does. The result that you are expecting is
based on there being a **c** and a **d** value matched. However, there isn't.
```
psql-11.5-5432-pgsql=# SELECT * FROM cypher('test', $$ MATCH
(a)-[:incs]->(c)-[d:incs]-() RETURN c,d $$) AS (c agtype, d agtype);
c | d
---+---
(0 rows)
psql-11.5-5432-pgsql=#
```
There isn't a path from **a** to **c** and then back to **a**, without
reusing an edge. That's why it returns nothing.
Hopefully this is helpful.
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