Mapping of nodes and relations returned as lists or maps

[steffen-harbich-cognitum]

Expected Behavior

Consider the following query:

MATCH (n:A) RETURN n, [(n)-[rn:REL_1]-(n2) | [rn, n2]]

I would expect OGM to map n2 to its @NodeEntity object and wire relations accordingly. Alternatives:

MATCH (n:A) RETURN n, [[(n)-[rn:REL_1]-(n2) | [rn, n2]]]
MATCH (n:A) RETURN n, [(n)-[rn:REL_1]-(n2) | {rn:rn, n2:n2}]

Current Behavior

None of the above queries is mapping the node n2 when calling session.query("...", Map.of(), true).

Possible Solution

If adapted to

MATCH (n:A) RETURN n, [(n)-[:REL_1]-(n2) | n2], [(n)-[rn:REL_1]-() | rn]

then it works but IMO this is an unnecessary repitition of the pattern comprehension. Please also note that the cypher generated by OGM when calling session.load has the same pattern as the first alternative query from above which implied my assumption that it should work.

Steps to Reproduce (for bugs)

Simple example project reproducing the issue:
demo.zip

Start gradle task :test in debug mode to fail the assertion, important code lines in NodeService class.

Context

See https://stackoverflow.com/questions/59481997 for background information.

Your Environment

• OGM Version used: 3.2.3
• Java Version used: 11
• Neo4J Version used: 3.5

[michael-simons]

I wonder if that is related to #666. Could you please test if your issues was there in 3.2.3 respectively 3.1.15?

[steffen-harbich-cognitum]

I don't think this is related to #666 because here (#737) it's a even a step before the actual wiring of @NodeEntity. Consider the case that REL_1 is not even modeled in my @NodeEntity but exists in the graph. Now if I query like above I still want to get the related node n2 to be mapped by OGM but of course OGM couldn't wire returned @NodeEntity with node n. And in fact that works when return statement is a list of nodes in contrast to list of lists.

In a nutshell, this issue is about OGM mapping "list of nodes" correctly but not "list of list of nodes" or "list of maps containing nodes" in query results.

Btw my demo project for reproduction uses OGM 3.2.3.

[michael-simons]

I cannot reproduce that issue in current 3.2 and master. I have attached an updated version of your demo project, that uses Neo4j-OGM 3.2.4 and it runs as well (
fixed-demo.zip)

See my article here if you need help upgrading Spring managed versions in you projects: https://michael-simons.github.io/simple-meetup/overriding-spring-managed-versions-in-gradle-projects.

Thanks for reporting.

[michael-simons]

For the record: Also fixed in Neo4j-OGM 3.1.16 (see
fixed-demo_boot2.1.11_ogm3.1.16.zip)

[steffen-harbich-cognitum]

Thanks! In fact, it is working with OGM version 3.2.4, so I will update. And thanks for the spring boot dependency tip, I didn't know it was that easy to adapt the version.

[michael-simons]

If you can wait till tomorrow, we will have 3.2.6 out. It fixes a performance and spring boot dev tools issue.

The upgrade with Maven is similar (use Maven properties in the pom.xml like <neo4j-ogm.version>3.2.6</neo4j-ogm.version>).

Thanks for your feedback, much appreciated.

[steffen-harbich-cognitum]

@michael-simons, is that intented that the query

MATCH (n:A) RETURN n, [(n)-[rn:REL_1]-(n2) | [rn, n2]]

will return only the relation rn as object but not n2 in list [rn, n2]? In my case I really need that object n2 because the relation rn is not modeled in my @NodeEntity (see again my SO question https://stackoverflow.com/questions/59481997, I need arbitrary relations between my @NodeEntities).

Tested with 3.2.6.

[michael-simons]

Thanks to the awesome @meistermeier I understood your problem better and we fixed that, too (and yes, we do think that this is a bug).

[steffen-harbich-cognitum]

Great news, so this will be included in 3.2.7?

[michael-simons]

Yep.

[michael-simons]

Hello @steffen-harbich-cognitum Here's a heads up for you: in #902 it was discovered that we flatten lists of known objects which shouldn't be the case as we don't do this for non-domain objects.

We are gonna fix that, but for your example it means a breaking change:

MATCH (n:Movie{title:'Pulp Fiction'}) return n, [(n)-[r:UNKNOWN]-(p) | [r,p]] as relAndNode

with the array around it, it will map to a List of node and relationships as it is actually correct (that's what a pattern comprehension produces).

A workaround to not change your calling code will be

MATCH (n:Movie{title:'Pulp Fiction'}) WITH n, [(n)-[r:UNKNOWN]-(p) | [r,p]] as patterns UNWIND patterns as relAndNode RETURN n, relAndNode

the mapping itself won't change.

Otherwise, the calling / usage side need a bit of change: It must now get the first index of the created pattern. See

neo4j-ogm/neo4j-ogm-tests/neo4j-ogm-integration-tests/src/test/java/org/neo4j/ogm/persistence/session/capability/QueryCapabilityTest.java

Lines 955 to 969 in 60e5f51

	@Test // GH-737
	public void shouldReturnListOfNodesAndRelationshipModelForUnknownRelationshipLists() {
	Result result = session
	.query("MATCH (n:Movie{title:'Pulp Fiction'}) return n, [(n)-[r:UNKNOWN]-(p) | [r,p]] as relAndNode",
	emptyMap());
	Map<String, Object> returnedRow = result.queryResults().iterator().next();
	assertThat(returnedRow.get("n")).isInstanceOf(Movie.class);
	assertThat(returnedRow.get("relAndNode")).isInstanceOf(List.class);
	List<?> relAndNode = ((List<List<?>>) returnedRow.get("relAndNode")).get(0);
	assertThat(relAndNode)
	.hasSize(2)
	.satisfies(v -> assertThat(v).isInstanceOf(Pet.class), Index.atIndex(0))
	.satisfies(v -> assertThat(v).isInstanceOf(RelationshipModel.class), Index.atIndex(1));
	}

Thank you and sorry for any possible inconvenience.

[steffen-harbich-cognitum]

Alright, thanks for info. I will keep that in mind when we update.