Where Union of Labels

[jtomek]

Hi, how do I run this?

SELECT * FROM cypher('playground', $$
MATCH (n:Movie|Person)
RETURN n
$$) AS (v agtype)

I get

Query 1 ERROR at Line 31: : ERROR:  syntax error at or near "|"
LINE 2: MATCH (n:Movie|Person)
                      ^

Is this the only way to get what I want?

SELECT * FROM cypher('playground', $$
MATCH (n)
WHERE label(n) = 'Movie' or label(n) = 'Person'
RETURN n
$$) AS (v agtype)

[rafsun42]

@jtomek There is a PR (#1452) for this feature. It is based on PG15.

[diangamichael]

It seems you're trying to execute Cypher queries within a PostgreSQL environment using the cypher function. The error you're encountering is due to the incorrect usage of the '|' symbol in the label definition within your MATCH clause. In Cypher, '|' is not used to denote multiple labels for a node. Instead, you should use the IN keyword.

Here's the corrected version of your first query:

sql
Copy code
SELECT * FROM cypher('playground', $$
MATCH (n)
WHERE n:Movie OR n:Person
RETURN n
$$) AS (v agtype);
This query will match nodes that have either the label 'Movie' or 'Person'.

Alternatively, you can use your second query as you provided:

sql
Copy code
SELECT * FROM cypher('playground', $$
MATCH (n)
WHERE label(n) = 'Movie' OR label(n) = 'Person'
RETURN n
$$) AS (v agtype);

Both queries should achieve the same result, with the second one explicitly checking the labels of nodes. Choose whichever you find more readable or preferable for your use case.

[rafsun42]

@diangamichael

In Cypher, '|' is not used to denote multiple labels for a node.

This is not correct. According to the openCypher specification, the pipe operator '|' is a valid way to define union of multiple labels.

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[alexgraul]

WHERE label(n) = 'Movie' OR label(n) = 'Person' works but is fairly ungainly. Per the openCypher spec (:Foo|Bar) should be supported.

[jrgemignani]

Apache AGE does not support multiple labels, yet. There is a PR in review that could add this in the future. However, it is a large PR and needs to be thoroughly reviewed.

[alexgraul]

Hey @jrgemignani thankyou for chiming in, aware of the multi-label PR but this is a separate issue with querying that's needed even with single-label support.

What should be possible is being able to OR between labels in a query which is relevant for single labels, not ANDing for situations where you want to match on multiple labels on a query (which I believe in openCypher terms is expressed as [:Foo:Bar]).
So if you have the following in your db:

(:City)-[:AirRoute]-(:City)
(:City)-[:SeaRoute]-(:City)

Being able to run a query and say 'Give me any Air OR Sea route between these two cities', which should be possible (in openCypher terms) via

(:City { name: 'London' })-[:SeaRoute|AirRoute]-(:City { name: :'Rotterdam' })

You can do it today via a WHERE clause as shown above but the syntax is super clunky.

[rafsun42]

Hi @alexgraul Although the PR refers it as 'multi-label', it does support the | operator for combining multiple single labels in MATCH queries. For now you can look at the regression test file to see what kind of multi-label queries are supported.

[alexgraul]

ohhh nice! Awesome, thankyou for clarifying!