For example, I have an entity like this:
#Data
#NodeEntity(label = "Subject")
public class Subject {
#GraphId
private Long id;
private String name;
#Relationship(type = "HAVE_S", direction = Relationship.OUTGOING)
private Set<Subject> children = new HashSet<>();
}
Then I need to query a 'Subject' by graphId;
#Query("MATCH (s:Subject)-[r:HAVE_S*1]->(c:Subject) WHERE ID(s) = {graphId} RETURN s, r, c;")
Subject findById(#Param("graphId") Long graphId);
The result I want just like the following json:
{
"id": 62
"name": "Java"
"children": [
{
"name": "Collection",
"id": 105
},
{
"name": "MultipleThreads",
"id": 0
}
]
}
But when I executed the cypher above through Spring Data, an error comes out and says "Result not of expected size. Expected 1 row but found 3".
I hope someone can help me with this problem, thanks.
As your model suggests A subject have multiple children so when you are fetching it by id it's returning a cartesian product of your subject* children. In this case you need to collect your children(subjects and then return)
#Query("MATCH (s:Subject)-[r:HAVE_S*1]->(c:Subject) WHERE ID(s) = {graphId} RETURN s, collect(c) as childrens;")
or simply you can use findById() of your repository the SDN will create query by itself
You can try like this.
MATCH (k:LabelsTree {name:'465afe3c118589de357745a709c0441f'}) CALL apoc.path.spanningTree(k,{labelFilter:'+LabelsTree', maxLevel:3, optional:true, filterStartNode:true}) yield path return path
Refer to the connection
Related
I have the nodes user and game with some relationships between them.
My REST API should return all relationships between the games and 1 user.
The cypher query i use is:
MATCH (u:User {id: '1234'} ) -[rel]- (game:Game) return game{.*, relationships: collect(DISTINCT rel)}
In my Neo4j Browser, everything works as expected and i see all properties i need.
But the GetMapping retuns everything except the relationship properties.
Neo4j Browser
{
"relationships": [
{
"identity": 54,
"start": 9,
"end": 8,
"type": "OWNED",
"properties": {
"ownedDate": "2021-07-03"
}
},
{
"identity": 45,
"start": 9,
"end": 8,
"type": "PLAYED",
"properties": {
"times": 5
}
}
],
"name": "Blood Rage",
"state": "ACTIVE",
"id": "1c152c91-4044-41f0-9208-0c436d6f6480",
"gameUrl": "https://asmodee.de/blood-rage"
}
GetMapping result (As you can see, the relationships are empty, but i have more empty JsonObjects, when there are more Relationships
{
"game": {
"relationships": [
{},
{}
],
"name": "Blood Rage",
"gameUrl": "https://asmodee.de/blood-rage",
"state": "ACTIVE",
"id": "1c152c91-4044-41f0-9208-0c436d6f6480"
}
}
The GetMapping is:
...
final ReactiveNeo4jClient client;
...
...
...
#GetMapping(value = { "/{id}/games"})
#RolesAllowed({"user", "admin"})
Flux<Map<String, Object>> findGamesByUser(#PathVariable String id){
String query = "MATCH (uuser:User {id: '" + id + "'} ) -[rel]- (game:Game) return game{.*, relationships: collect(DISTINCT rel)}";
return client.query(query).fetch().all();
}
A RelationshipProperty-Example
#RelationshipProperties
#Data
#Builder
public class PlayedGame {
#Id
#GeneratedValue
private Long relationshipId;
#Property
int times = 0;
#TargetNode private GameEntity game;
public int addPlay(){
this.times = this.times + 1;
return this.times;
}
}
What do i have to change in my GetMapping to show the relationship-properties?
Thank you,
Kevin
You need to return the actual nodes and relationships, otherwise you're missing the id-mapping.
There should be examples in the SDN docs.
Best if you have a small reproducible example (e.g. with the default movies graph).
Not sure if there is something off in your SDN setup, in general for such simple queries you should be able to just use a repository and not need to write cypher queries by hand.
The general information given by Michael is correct but there is more in you question:
First of all the meta domain model is completely ignored if you are using the Neo4jClient. It does not automatically map anything back but uses the driver's types.
As a result you will end up with an (current state of this answer) InternalRelationship which does not have any getter-methods.
I assume that you are serializing the result in the application with Jackson. This is the reason why you see objects that represent the relationships but without any content within.
If you want to get things mapped for you, create also the domain objects properly and use (at least) the Neo4jTemplate with your query.
If you model User, Game, and the relationship properties like PlayedGame correctly, a
neo4jTemplate.findAll("MATCH (u:User)<-[rel]-(g:Game) return u, collect(rel), collect(g)", User.class)
will map the results properly. Also if this is all you have, you could also skip the custom query at all and use
neo4jTemplate.findAll(User.class)
or
neo4jTemplate.findById(useId, User.class)
I've a single object in the #Param to be used in #Query whereas the 1st level fields can be accessed without issues, but not the 2nd level. Unable to access fields from Language object
Consider:
{
"id": 0,
"description": "some text",
"language": {
"name": "English"
}
}
#RelationshipProperties
#Data
public class KnowsEntity {
#Id
#GeneratedValue()
private Long id;
#Property
private String description;
#TargetNode
private Language language;
}
#Query("MATCH (y:PERSON {nid: $from})-[r:KNOWS]->(e:LANGUAGE {name: $rel.__language__.__name__ }) \n" +
"WHERE ID(r) = $rel. id SET r.description = $rel.__description__ \n" +
"return y, collect(r), collect(e)")
UpdatedLanguageProjection updateRel(#Param("from") String from, #Param("rel") KnowsEntity relation);
form the above query i could access the first level field $rel.__description__ and not the field inside first level object $rel.__language__.__name__ (2nd level)
can someone please correct / suggest me an option to get this?
I got this worked with the following SpEL way
https://docs.spring.io/spring-data/neo4j/docs/6.1.1/reference/html/#custom-queries.spel
eg: {name: :#{#rel.language.name}}
my relationship graph as below pic
Using MATCH (n:Person {name:'1'})-[]-()-[r]-(m) RETURN m,r will return "4" and "5",but cannot get the relationship between "4" and "5",actually,"4" follow "5","r" just represent the friends of 4(4-->2) and 5(5-->3).
In spring data neo4j
domain.java
#NodeEntity(label = "Person")
public class PersonTest {
#Id
private Long id;
#Property(name = "name")
private String name;
#Relationship(type = "Follow") //direction=Relationship.DIRECTION
private List<PersonTest> friends;
Repository.java
public interface PersonRepository extends Neo4jRepository<PersonTest,Long> {
#Query("MATCH (n:Person {name:{name}})-[]-()-[r]-(m) RETURN m,r")
Collection<PersonTest> graph(#Param("name") String name);
}
Service.java
Collection<PersonTest> persons = personRepository.graph(name);
Iterator<PersonTest> result = persons.iterator();
while (result.hasNext()) {
for (PersonTest friend : p.getFriends()) {
//........here will get 2 and 3!
}
}
How to resolve this problem??get the relationship between "4" and "5".
To find related children at a certain level, you can use a two-sided pattern of variable length:
MATCH (n:Person {name:'1'})-[:Follow*2]->(m)-[r:Follow]-()<-[:Follow*2]-(n)
RETURN m,r
http://console.neo4j.org/r/el2x80
Update. I think that this is a more correct query:
MATCH (n:Person {name:'1'})-[:Follow*2]->(m:Person)-[r:Follow]-(k:Person)
WHERE (n)-[:Follow*2]->(k)
RETURN m, r
http://console.neo4j.org/r/bv2u8k
I am trying to create multiple nodes in Neo4j using Cypher by passing properties as parameters as part of an UNWIND function, but I keep receiving the error Type mismatch: expected Collection<T> but was Map.
This happens even when using the following example from the Neo4j documentation (link):
UNWIND {
props : [ {
name : "Andres",
position : "Developer"
}, {
name : "Michael",
position : "Developer"
} ]
} AS map
CREATE (n)
SET n = map
Can anyone point out what I am doing wrong here?
Note, the example above is not exactly as in the Neo4j documentation. Their example wraps the property names in double quotes, but this causes my instance of Neo4j to throw the errorInvalid input '"': expected whitespace...)
UNWIND is expecting a collection, not a map as you're currently passing in, try this instead (just remove the wrapping curly braces and prop top level field):
UNWIND [ {
name : "Andres",
position : "Developer"
}, {
name : "Michael",
position : "Developer"
} ] AS map
CREATE (n)
SET n = map
Chris's answer is of course the correct one, but here's why your solution doesn't work when you're following the documentation: you're not copying the documentation.
The documentation shows the use of a named parameter:
UNWIND { props } AS map
CREATE (n)
SET n = map
with props passed in the map of parameters, which would look like:
{
"props" : [ {
"name" : "Andres",
"position" : "Developer"
}, {
"name" : "Michael",
"position" : "Developer"
} ]
}
if you displayed the map as JSON. It means the {props} placeholder will be replaced by the value for the props key. Which is exactly what Chris did.
Here's what the Java code would look like:
GraphDatabaseService db = /* init */;
Map<String, Object> andres = new HashMap<>();
andres.put("name", "Andres");
andres.put("position", "Developer");
Map<String, Object> michael = new HashMap<>();
michael.put("name", "Michael");
michael.put("position", "Developer");
Map<String, Object> params = new HashMap<>();
params.put("props", Arrays.asList(andres, michael));
try (Transaction tx = db.beginTx()) {
db.execute("UNWIND {props} AS map CREATE (n) SET n = map", params);
tx.success();
}
I have a database including PlayStation games and it contains games from all regions and platforms. Some of the games from different regions have the same title and platform so I would like to filter out "duplicates". At this time, I don't have region information on each game so the best I can do is filter out by game name and platform.
Is it possible to select distinct nodes by property? I seem to remember that you can return distinct rows based on a column in SQL, but it seems that Cypher applies distinct to the entire row and not just a specific column.
I would like to achieve something like the following:
MATCH (game:PSNGame) RETURN game WHERE distinct game.TitleName, distinct game.Platforms
The above query if it were valid would return all PSNGame nodes with a distinct TitleName and Platforms combination. Since the above query is not valid Cypher, I have tried returning a list of distinct TitleName/Platforms where distinct is applied to both columns.
The query I have for returning the distinct TitleName/Platforms list looks like this:
MATCH (game:PSNGame) RETURN distinct game.TitleName, game.Platforms
The JSON response from Neo4j is similar to this:
[["God of War", ["PS3", "PSVITA"]], ["God of War II", ["PS3", "PSVITA"]]]
The problem I'm facing is that the JSON response is not really an object with properties. It's more of an array of arrays. If I could get the response to be more like an object, I could deserialize without issues. I tried to deserialize as an IList<PsnGame>, but haven't had much luck.
Here's my POCO for the IList<PsnGame> implementation:
public class PsnGame
{
public string TitleName { get; set; }
public string[] Platforms { get; set; }
}
EDIT:
Here is the simplest example of my Neo4jClient query:
// helper function for handling searching by name and platform
private ICypherFluentQuery BuildPSNGamesQuery(string gameName, string platform)
{
var query = client.Cypher
.Match("(g:PSNGame)");
if (!string.IsNullOrWhiteSpace(gameName))
{
query = query.Where($"g.TitleName =~ \"(?i).*{gameName}.*\"");
if (!string.IsNullOrWhiteSpace(platform) && platform.ToLower() != "all")
{
query = query.AndWhere($"\"{platform}\" in g.Platforms");
}
}
else
{
if (!string.IsNullOrWhiteSpace(platform) && platform.ToLower() != "all")
{
query = query.Where($"\"{platform}\" in g.Platforms");
}
}
return query;
}
Distinct games:
var distinctGames = await BuildPSNGamesQuery(gameName, platform)
.With("DISTINCT g.TitleName AS TitleName, g.Platforms AS Platforms")
.With("{ TitleName: TitleName, Platforms: Platforms } as Games")
.OrderBy("TitleName")
.Return<PsnGame>("Games")
.Skip((pageNumber - 1) * pageSize)
.Limit(pageSize)
.ResultsAsync;
All games (somehow need to filter based on previous query):
var results = await BuildPSNGamesQuery(gameName, platform)
.Return(g => new Models.PSN.Composite.PsnGame
{
Game = g.As<PsnGame>()
})
.OrderBy("g.TitleName")
.Skip((pageNumber - 1) * pageSize)
.Limit(pageSize)
.ResultsAsync;
By using a map, I'm able to return the TitleName/Platforms pairing that I want, but I suspect I'll need to do a collect on the Platforms to get all platforms for a particular game title. Then I can filter the entire games list by the distinctGames that I return. However, I would prefer to perform a request and merge the queries to reduce HTTP traffic.
An example of duplicates can be seen on my website here:
https://www.gamerfootprint.com/#/games/ps
Also, the data for duplicates looks something like this:
MATCH (n:PSNGame)
WHERE n.TitleName = '1001 Spikes'
RETURN n.TitleName, n.Platforms LIMIT 25
JSON:
{
"columns":[
"n.TitleName",
"n.Platforms"
],
"data":[
{
"row":[
"1001 Spikes",
[
"PSVITA"
]
],
"graph":{
"nodes":[
],
"relationships":[
]
}
},
{
"row":[
"1001 Spikes",
[
"PS4"
]
],
"graph":{
"nodes":[
],
"relationships":[
]
}
}
],
"stats":{
"contains_updates":false,
"nodes_created":0,
"nodes_deleted":0,
"properties_set":0,
"relationships_created":0,
"relationship_deleted":0,
"labels_added":0,
"labels_removed":0,
"indexes_added":0,
"indexes_removed":0,
"constraints_added":0,
"constraints_removed":0
}
}
EDIT: 10-31-15
I was able to get distinct game title and platforms returning with the platforms for each game rolled up into a single collection. My new query is the following:
MATCH (game:PSNGame)
WITH DISTINCT game.TitleName as TitleName,
game.Platforms as coll UNWIND coll as Platforms
WITH TitleName as TitleName, COLLECT(DISTINCT Platforms) as Platforms
RETURN TitleName, Platforms
ORDER BY TitleName
Here is a small subset of the results:
{
"columns":[
"TitleName",
"Platforms"
],
"data":[
{
"row":[
"1001 Spikes",
[
"PSVITA",
"PS4"
]
],
"graph":{
"nodes":[
],
"relationships":[
]
}
}
],
"stats":{
"contains_updates":false,
"nodes_created":0,
"nodes_deleted":0,
"properties_set":0,
"relationships_created":0,
"relationship_deleted":0,
"labels_added":0,
"labels_removed":0,
"indexes_added":0,
"indexes_removed":0,
"constraints_added":0,
"constraints_removed":0
}
}
Finally, 1001 Spikes is in the list once and has both PS VITA and PS4 listed as platforms. Now, I need to figure out how to grab the full game nodes and filter against the above query.
try this one:
MATCH (game:PSNGame)
with game, collect([game.TitleName, game.Platforms]) as wow
return distinct(wow)
If I understand you correctly, you want to select different nodes by property and remove duplicates? If so, it would be something like this:
MATCH (game:PSNGame {property:'value'}) RETURN DISTINCT game.property
That should remove duplicates and return your node by property.