Procedure apoc.meta.subgraph return wrong type with includeLabels not existent

[neo-technology-build-agent]

Issue by vga91
Monday May 17, 2021 at 10:35 GMT
Originally opened as neo4j-contrib/neo4j-apoc-procedures#1906

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Expected Behavior (Mandatory)

Should return nodes: [] and relationships: []

Actual Behavior (Mandatory)

The procedure returns a node with dataset total count.

How to Reproduce the Problem

Simple Dataset (where it's possibile)

CREATE (:Foo), (:Bar)

Steps (Mandatory)

1. CALL apoc.meta.subGraph({labels:["Test"],rels:[],excludes:[]})
2. Returns a "Test" node with count 2, even if the label does not exist

Screenshots (where it's possibile)

Currently used versions

Versions

• Neo4j: 4.0.11
• Neo4j-Apoc: 4.0.0.18

[neo-technology-build-agent]

Comment by vga91
Monday May 17, 2021 at 12:57 GMT

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Related to #1491 (Same root cause, but without rels)

[hvub]

Here is a little more detailed variant (on 5.25.1)

Setup:

MATCH (n) DETACH DELETE n
WITH COUNT(1) as foo
CREATE (:Foo), (:Bar), (:Test) // label Test created here
WITH COUNT(1) as foo
MATCH (t:Test) DELETE t // node with label Test delete again
WITH COUNT(1) as foo
MATCH (n)
RETURN n

Query 1:

CALL apoc.meta.subGraph({includeLabels:["Test"],rels:[],excludes:[]})

=> correct result

Query 2:

CALL apoc.meta.subGraph({includeLabels:["X"],rels:[],excludes:[]})

=> wrong result

In other words, truly unknown labels are effected.

Note that

CALL db.labels

is not indicator which labels are effected, since it does not return Test label after the above setup query.

The same issue appear on the function apoc.meta.nodes.count. On the above setup:

RETURN apoc.meta.nodes.count(["Test"]) AS cnt

correctly returns

╒═══╕
│cnt│
╞═══╡
│0  │
└───┘

while

RETURN apoc.meta.nodes.count(["X"]) AS cnt

erroneously returns

╒═══╕
│cnt│
╞═══╡
│2  │
└───┘

Like the result of apoc.meta.nodes.count, the count property on the create virtual node wrongly created by apoc.meta.subGraph seems to always be 2.

[hvub]

A similar problem also exists for relationship types.

Setup

MATCH (n) DETACH DELETE n
WITH COUNT(1) as foo
CREATE (:Foo)-[:R]->(:Bar)-[:Rtest]->(:Test)
WITH COUNT(1) as foo
MATCH (t:Test) DETACH DELETE t
WITH COUNT(1) as foo
MATCH (n)
RETURN n

Query 1:

CALL apoc.meta.subGraph({includeLabels:["R"],rels:[],excludes:[]})

=> correct result

Query 2:

CALL apoc.meta.subGraph({includeLabels:[],rels:["Rtest"],excludes:[]})

=> correct result

Query 3:

CALL apoc.meta.subGraph({includeLabels:[],rels:["X"],excludes:[]})

=> wrong result

Here the made up count is 1 though.

Query 4:

CALL apoc.meta.subGraph({includeLabels:["Bar"],rels:["X"],excludes:[]})

=> correct result, interestingly

Query 5:

CALL apoc.meta.subGraph({includeLabels:["X"],rels:["X"],excludes:[]})

=> wrong result, again