Trying to execute the following cypher query (which executes ok from neoclipse)
START a=node(*) MATCH a-[:Knows]->p WHERE (p.Firstname! = "Steve" ) RETURN p
from neo4jclient with the following statement
protected void Populate()
{
var client = new GraphClient(new Uri("http://altdev:7474/db/data"));
client.Connect();
var query = client.Cypher
.Start(new RawCypherStartBit("all", "node(*)"))
.Match("all-[:Knows]->p")
.Where((Person p) => p.Firstname == "Steve")
.Return<Node<Person>>("Person");
var people = query.Results;
}
the client throws an exception, as follows
The query was: START all=node(*)
MATCH all-[:Knows]->p
WHERE (p.Firstname! = {p0})
RETURN Person
The response status was: 400 Bad Request
The response from Neo4j (which might include useful detail!) was: {
"message" : "Unknown identifier `Person`.",
"exception" : "SyntaxException",
"fullname" : "org.neo4j.cypher.SyntaxException",
"stacktrace" : [ "org.neo4j.cypher.internal.symbols.SymbolTable.evaluateType(SymbolTable.scala:59)", "org.neo4j.cypher.internal.commands.expressions.Identifier.evaluateType(Identifier.scala:47)", "org.neo4j.cypher.internal.commands.expressions.Expression.throwIfSymbolsMissing(Expression.scala:52)", "org.neo4j.cypher.internal.pipes.ColumnFilterPipe$$anonfun$throwIfSymbolsMissing$1.apply(ColumnFilterPipe.scala:61)", "org.neo4j.cypher.internal.pipes.ColumnFilterPipe$$anonfun$throwIfSymbolsMissing$1.apply(ColumnFilterPipe.scala:61)", "scala.collection.immutable.List.foreach(List.scala:309)", "org.neo4j.cypher.internal.pipes.ColumnFilterPipe.throwIfSymbolsMissing(ColumnFilterPipe.scala:61)", "org.neo4j.cypher.internal.pipes.PipeWithSource.<init>(Pipe.scala:63)", "org.neo4j.cypher.internal.pipes.ColumnFilterPipe.<init>(ColumnFilterPipe.scala:30)", "org.neo4j.cypher.internal.executionplan.builders.ColumnFilterBuilder.handleReturnClause(ColumnFilterBuilder.scala:60)", "org.neo4j.cypher.internal.executionplan.builders.ColumnFilterBuilder.apply(ColumnFilterBuilder.scala:38)", "org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl.prepareExecutionPlan(ExecutionPlanImpl.scala:54)", "org.neo4j.cypher.internal.executionplan.ExecutionPlanImpl.<init>(ExecutionPlanImpl.scala:36)", "org.neo4j.cypher.ExecutionEngine$$anonfun$prepare$1.apply(ExecutionEngine.scala:80)", "org.neo4j.cypher.ExecutionEngine$$anonfun$prepare$1.apply(ExecutionEngine.scala:80)", "org.neo4j.cypher.internal.LRUCache.getOrElseUpdate(LRUCache.scala:37)", "org.neo4j.cypher.ExecutionEngine.prepare(ExecutionEngine.scala:80)", "org.neo4j.cypher.ExecutionEngine.execute(ExecutionEngine.scala:72)", "org.neo4j.cypher.ExecutionEngine.execute(ExecutionEngine.scala:76)", "org.neo4j.cypher.javacompat.ExecutionEngine.execute(ExecutionEngine.java:79)", "org.neo4j.server.rest.web.CypherService.cypher(CypherService.java:94)", "java.lang.reflect.Method.invoke(Method.java:616)", "org.neo4j.server.rest.security.SecurityFilter.doFilter(SecurityFilter.java:112)" ]
}
As you can see, essentially the queries are the same. And the nodes I'm trying to get are of _type "Person"
TIA
Marcelo
In your MATCH clause you use the identity p:
.Match("all-[:Knows]->p") // becomes MATCH all-[:Knows]->p
In your RETURN clause you change to using the identity Person:
.Return<Node<Person>>("Person"); // becomes RETURN person
You need to pick one and be consistent.
Integrating some other clean up too, your full query should be:
var query = client.Cypher
.Start(new { all = All.Nodes })
.Match("all-[:Knows]->p")
.Where((Person p) => p.Firstname == "Steve")
.Return<Person>("p");
It's down to the way you are creating the Cypher code, specifically what you are returning:
var query = client.Cypher
.Start(new RawCypherStartBit("all", "node(*)"))
.Match("all-[:Knows]->p")
.Where((Person p) => p.Firstname == "Steve")
.Return<Node<Person>>("p"); // <-- THIS LINE SHOULD SAY 'P' NOT 'Person'
The return statement requires the name to be the same as the node you have defined. So you use: all-[:knows]->p where you define p. Now you need to return it.
(Which is what Peter is saying in his answer :))
You are trying to return a Person node that is not assigned to anything in the query.
Related
I am trying to get a path from a base node to its root node as 1 row. The Cypher query looks like this:
start n = node:node_auto_index(Name = "user1") match path = (n-[r:IS_MEMBER_OF_GROUP*]->b) return last(collect(distinct path));
But when changing this over to the Neo4JClient syntax:
var k = clientConnection.Cypher
.Start(new { n = "node:node_auto_index(Name = 'user1')" })
.Match("path = (n-[r:IS_MEMBER_OF_GROUP*]->b)")
.ReturnDistinct<Node<Principles>>("last(collect(path))").Results;
It gets an error:
{"Value cannot be null.\r\nParameter name: uriString"}
When continuing on from there:
Neo4jClient encountered an exception while deserializing the response from the server. This is likely a bug in Neo4jClient.
Please open an issue at https://bitbucket.org/Readify/neo4jclient/issues/new
To get a reply, and track your issue, ensure you are logged in on BitBucket before submitting.
Include the full text of this exception, including this message, the stack trace, and all of the inner exception details.
Include the full type definition of Neo4jClient.Node`1[[IQS_Neo4j_TestGraph.Nodes.Principles, IQS Neo4j TestGraph, Version=1.0.0.0, Culture=neutral, PublicKeyToken=null]].
Include this raw JSON, with any sensitive values replaced with non-sensitive equivalents:
{
"columns" : [ "last(collect(path))" ],
"data" : [ [ {
"start" : "http://localhost:7474/db/data/node/3907",
"nodes" : [ "http://localhost:7474/db/data/node/3907", "http://localhost:7474/db/data/node/3906", "http://localhost:7474/db/data/node/3905", "http://localhost:7474/db/data/node/3904" ],
"length" : 3,
"relationships" : [ "http://localhost:7474/db/data/relationship/4761", "http://localhost:7474/db/data/relationship/4762", "http://localhost:7474/db/data/relationship/4763" ],
"end" : "http://localhost:7474/db/data/node/3904"
} ] ]
}
How would one convert the cypher query to Neo4JClient query?
Well, the thing you are returning is a PathsResult not a Node<>, so if you change your query to be:
var k = clientConnection.Cypher
.Start(new { n = "node:node_auto_index(Name = 'user1')" })
.Match("path = (n-[r:IS_MEMBER_OF_GROUP*]->b)")
.ReturnDistinct<PathsResult>("last(collect(path))").Results; //<-- Change here
you will get results, this returns what I get from running your query against my db, if you specifically want the nodes this post: Getting PathsResults covers converting to actual nodes and relationships.
One other thing, (and this will help the query perform better as neo4j can cache the execution plans easier), is that you can change your start to make it use parameters by doing:
.Start(new { n = Node.ByIndexLookup("node_auto_index", "Name", "user1")})
I am trying to put a where clause in my Neo4j cypher query to return some nodes, this is the query im trying to perform:
start n = node:node_auto_index(Name = "Contact Details") Match (n)--(x) Where x.Type = "Version" Return x;
Now my C# method looks like this(using Neo4jClient):
public IEnumerable<Node<VersionNode>> GraphGetAllVersionNodes(string nodeName)
{
clientConnection = graphOperations.GraphGetConnection();
IEnumerable<Node<VersionNode>> queryResult = null;
var query = clientConnection
.Cypher
.Start(new
{
n = Node.ByIndexLookup("node_auto_index", "Name", nodeName)
})
.Match("(n)--(x)")
.Where((VersionNode x) => x.Type = "Version")
.Return<Node<VersionNode>>("(x)")
.Results;
queryResult = query.ToList();
return queryResult;
}
Now there is an error on the where clause saying:
Cannot convert lambda expression to type 'string' because it is not a delegate type
What am I doing wrong here?
Thanks
If that's a verbatim copy-paste, then I'm guessing the issue is that you wrote:
.Where((VersionNode x) => x.Type = "Version")
When you need to write:
.Where((VersionNode x) => x.Type == "Version")
PS. What's the point of IEnumerable<Node<VersionNode>> queryResult = null; instead of just var queryResult =? You never assign it in any other path, so it's just a waste of code and an extra signature to maintain.
I am using Azure and finding the performance to be slow. In order to reduce the round trip time, I am clubbing the following queries into one query.
var queryItem = _graphClient
.Cypher
.Start(new
{
n = Node.ByIndexLookup("item_idx", "SKU", sSKU1),
})
.Return<Node<Item>>("n");
somewhere else in the code I have following statements
var queryItem = _graphClient
.Cypher
.Start(new
{
m = Node.ByIndexLookup("item_idx", "SKU", sSKU2),
})
.Return<Node<Item>>("m");
I tried to combine above two queries into a single query like this
var queryItem = _graphClient
.Cypher
.Start(new
{
n = Node.ByIndexLookup("item_idx", "SKU", sSKU1),
m = Node.ByIndexLookup("item_idx", "SKU", sSKU2),
})
.Return<Node<Item>>("n");
I know above is only for single column so I tried using following return statement
.Return((n, m) => new
{
N = n.CollectAs<Node<Item>>(),
M = m.CollectAs<Node<Item>>()
});
but then I have problems with the following statement
Node<Item> item1 = itemQueryResult.First();
It says Error Cannot implicitly convert type 'AnonymousType#1' to 'Neo4jClient.Node.
Can you please suggest a simple syntax or returning multiple columns and a way to extract the first node? TIA.
I think what you're missing here is that the Return statement returns one object per Cypher row.
Your query is returning a table like this:
|-----------------|
| n | m |
|-----------------|
| Node | Node |
|------------------
That's one table, with one row, with two columns.
In this statement, you are returning an anonymous type per Cypher row:
.Return((n, m) => new
{
N = n.CollectAs<Node<Item>>(),
M = m.CollectAs<Node<Item>>()
});
The return type of that method is IEnumerable<AnonymousType>.
You're then trying to get the first row (an anonymous type) and implicitly cast that to Node<Item>, which is not valid.
You should get the row, then get the properties within it.
Some other things to note:
You don't want to use CollectAs in this scenario: that will turn each cell of your table into an array with a single value, which just adds more indirection.
.As<Node<T>>() can be written as .Node<T>()
With that in mind, here's the query you want:
var result = _graphClient
.Cypher
.Start(new
{
n = Node.ByIndexLookup("item_idx", "SKU", sSKU1),
m = Node.ByIndexLookup("item_idx", "SKU", sSKU2),
})
.Return((n, m) => new
{
N = n.Node<Item>(),
M = m.Node<Item>()
})
.Results
.Single();
var n = result.N;
var m = result.M;
Make sense?
PS: I hope you aren't actually clubbing anything. Baby seals don't like that. You are combining queries.
I am try to perform a query on my NameIndex in Neo4j using the Neo4jClient for .NET but i get this error:
{"Received an unexpected HTTP status when executing the request.\r\n\r\nThe response status was: 500 Internal Server Error\r\n\r\nThe raw response body was: {\"exception\":\"NullPointerException\",\"stacktrace\":[\"org.apache.lucene.util.SimpleStringInterner.intern(SimpleStringInterner.java:54)\",\"org.apache.lucene.util.StringHelper.intern(StringHelper.java:39)\",\"org.apache.lucene.index.Term.<init>(Term.java:38)\",\"org.apache.lucene.queryParser.QueryParser.getFieldQuery(QueryParser.java:643)\",\"org.apache.lucene.queryParser.QueryParser.Term(QueryParser.java:1421)\",\"org.apache.lucene.queryParser.QueryParser.Clause(QueryParser.java:1309)\",\"org.apache.lucene.queryParser.QueryParser.Query(QueryParser.java:1237)\",\"org.apache.lucene.queryParser.QueryParser.TopLevelQuery(QueryParser.java:1226)\",\"org.apache.lucene.queryParser.QueryParser.parse(QueryParser.java:206)\",\"org.neo4j.index.impl.lucene.IndexType.query(IndexType.java:300)\",\"org.neo4j.index.impl.lucene.LuceneIndex.query(LuceneIndex.java:227)\",\"org.neo4j.server.rest.web.DatabaseActions.getIndexedNodesByQuery(DatabaseActions.java:977)\",\"org.neo4j.server.rest.web.DatabaseActions.getIndexedNodesByQuery(DatabaseActions.java:960)\",\"org.neo4j.server.rest.web.RestfulGraphDatabase.getIndexedNodesByQuery(RestfulGraphDatabase.java:692)\",\"java.lang.reflect.Method.invoke(Unknown Source)\"]}"}
My method looks as follows:
public IEnumerable GraphGetNodeByName(string NodeName)
{
GraphOperationsLogger.Trace("Now entering GraphGetNodeByName() method");
IEnumerable QueryResult = null;
GraphOperationsLogger.Trace("Now performing the query");
var query = client_connection.QueryIndex<GraphNode>("NameIndex", IndexFor.Node,
//Here I want to pass in the NodeName into the query
//#"Start n = node:NameIndex(Name = '"+ NodeName +"') return n;");
//Here I am hard-coding the NodeName
#"Start n = node:NameIndex(Name = ""Mike"") return n;");
QueryResult = query.ToList();
return QueryResult;
}
I ideally would like to pass in the NodeName into the query but that is not working therefore I have tried hard-coding it in and that also doesn't work. Both scenarios produce the same error message?
The method you are calling, IGraphClient.QueryIndex is not a Cypher method. It's a wrapper on http://docs.neo4j.org/chunked/milestone/rest-api-indexes.html#rest-api-find-node-by-query. It's an older API, from before Cypher existed.
You're already half way there though, because your code comments include the Cypher query:
Start n = node:NameIndex(Name = "Mike")
return n;
So, let's just translate that into C#:
client
.Cypher
.Start(new CypherStartBitWithNodeIndexLookup("n", "NameIndex", "Name", "Mike"))
.Return<Node<Person>>("n");
Always start your Cypher queries from IGraphClient.Cypher or NodeReference.StartCypher (which is just a shortcut to the former).
There are some other issues with your method:
You're returning a raw IEnumerable. What is in it? You should return IEnumerable<T>.
You're calling query.ToList(). I'd be surprised if that even compiles. You want to call ToList on the results so that the enumerable is hit.
In C#, your local variables should be in camelCase not PascalCase. That is, queryResult instead of QueryResults.
Combining all of those points, your method should be:
public IEnumerable<Person> GetPeopleByName(string name)
{
return graphClient
.Cypher
.Start(new CypherStartBitWithNodeIndexLookup("n", "NameIndex", "Name", "Mike"))
.Return<Node<Person>>("n")
.Results
.ToList();
}
Some pseudo-code of the model I'm working with:
User { int Id, string Username }
Activity { int Id, string Name }
Place { int Id, string Name }
Basically I have a bunch of Users and they belong to certain places (many to many relationship in RDBMS world). What I'd like to do now that I've created all of the nodes already is create the relationship between them. To do that I believe I need to get references to each node and then simply create the relationship between them.
Note: So far no relationships exist. It does look like in some of the examples they have added the User nodes with a relationship that points to the RootNode but I have no idea why. I'm not sure if I need to do that or not.
More pseudo-code:
var userRef = _graphClient...GetUserNodeWhereIdEquals(user.Id);
// or something like _graphClient.OutV<User>("[[id={0}]]", user.Id)
// or even just _graphClient.V<User>(id == user.Id)
var placeRef = _graphClient...GetPlaceNodeWhereIdEquals(place.Id);
_graphClient...CreateRelationshipBetween(userRef, placeRef, "belongs_to");
Unfortunately the documentation starts off pretty great then goes south when you get to relationships.
Update 3/29/12
Here's the code I have so far:
foreach (var a in _activityTasks.GetAll())
{
_graphClient.Create(a, new ActivityBelongsTo(_graphClient.RootNode));
}
foreach (var p in _placeTasks.GetAll().Take(1))
{
var placeNode = _graphClient.Create(p, new PlaceBelongsTo(_graphClient.RootNode));
foreach (var activity in p.Activities)
{
Activity activity1 = activity;
var activityNode = _graphClient.RootNode.In<Activity>(ActivityBelongsTo.TypeKey, a => a.Id == activity1.Id).SingleOrDefault();
_graphClient.CreateRelationship(placeNode, new PlaceHasActivity(activityNode.Reference));
}
}
The activity nodes are created fine. The place node is created fine. An error is now being thrown when trying to get the activityNode. It's a rather large stack trace so I'll try to paraphrase here:
Received an exception when executing the request.
The query was: g.v(p0).in(p1).filter{ it[p2] == p3
}.drop(p4).take(p5)._()
The exception was: Value cannot be null. Parameter name: key
System.ArgumentNullException: Value cannot be null.Parameter name: key
at System.Collections.Generic.Dictionary`2.Insert(TKey key, TValue
value, Boolean add) ... The raw response body was: [ {
"outgoing_relationships" :
"http://localhost:7474/db/data/node/2/relationships/out", "data" : {
"Name" : "Aerobics", "Id" : 2 }, "all_typed_relationships" :
"http://localhost:7474/db/data/node/2/relationships/all/{-list|&|types}",
"traverse" :
"http://localhost:7474/db/data/node/2/traverse/{returnType}", "self"
: "http://localhost:7474/db/data/node/2", "property" :
"http://localhost:7474/db/data/node/2/properties/{key}",
"outgoing_typed_relationships" :
"http://localhost:7474/db/data/node/2/relationships/out/{-list|&|types}",
"properties" : "http://localhost:7474/db/data/node/2/properties",
"incoming_relationships" :
"http://localhost:7474/db/data/node/2/relationships/in", "extensions"
: { }, "create_relationship" :
"http://localhost:7474/db/data/node/2/relationships",
"paged_traverse" :
"http://localhost:7474/db/data/node/2/paged/traverse/{returnType}{?pageSize,leaseTime}",
"all_relationships" :
"http://localhost:7474/db/data/node/2/relationships/all",
"incoming_typed_relationships" :
"http://localhost:7474/db/data/node/2/relationships/in/{-list|&|types}"
} ]
Something to do when adding a item to a Dictionary when the key is null. Problem is, I don't see any nulls when I debug on my end, activity1 is there, RootNode is there, TypeKey is a const string.
I'm almost wondering if I should just keep the created nodes within a array or Dictionary myself and then just working with the NodeReference. That's what I'm going to try next.
Later that morning
This seems to load everything into the graph database fine:
var activityNodes = _activityTasks.GetAll().ToDictionary(a => a.Id, a => _graphClient.Create(a, new ActivityBelongsTo(_graphClient.RootNode)));
foreach (var p in _placeTasks.GetAll())
{
var placeNode = _graphClient.Create(p, new PlaceBelongsTo(_graphClient.RootNode));
foreach (var activity in p.Activities)
{
_graphClient.CreateRelationship(placeNode, new PlaceHasActivity(activityNodes[activity.Id]));
}
}
foreach (var u in _userTasks.GetAllUserGraph())
{
var userNode = _graphClient.Create(u, new UserBelongsTo(_graphClient.RootNode));
foreach(var activity in u.Activities)
{
_graphClient.CreateRelationship(userNode, new UserParticipatesIn(activityNodes[activity.Id]));
}
}
Now the problem is similar to what I had before. Now I want to get an activity that has a relationship to the RootNode:
Node<Activity> activity = _graphClient
.RootNode
.In<Activity>(ActivityBelongsTo.TypeKey, a => a.Id == 1)
.SingleOrDefault();
Throwing the key value can't be null exception again. I think I need to investigate the gremlin syntax more. I'm guessing the problem is there.
This afternoon
Started to experiment with Gremlin queries:
g.v(0).inE.filter{it.label=="ACTIVITY_BELONGS_TO"}.outV.filter{it.Id==1}.Name
works fine. I tried to replicate that using neo4jClient syntax:
_graphClient.RootNode.InE(ActivityBelongsTo.TypeKey).OutV(b => b.Id == 1).SingleOrDefault();
Same null exception, it spits out:
g.v(p0).inE.filter{ it[p1].equals(p2) }.outV.filter{ it[p3] == p4 }.drop(p5).take(p6)._()
which looks right to me, except for the end. Ran this though:
g.v(0).inE.filter{it.label=="ACTIVITY_BELONGS_TO"}.outV.filter{it.Id==1}.drop(0).take(1)._()
And that works fine. Something stinks here...maybe I should try the other library although I liked the de/serialization support. Sigh...
Thought maybe a raw query would work. Nope! This method no longer accepts a string and the required GremlinQuery I have no idea how to you. Grooooooooooooooooan.
var users = graphClient.ExecuteGetAllNodesGremlin<IsCustomer>("g.v(0).out('IsCustomer'){it.'Name' == 'BobTheBuilder'}");
Update 3/30/12
Created a new project, everything below works fine. Super confused why it will work here... :( Maybe version differences, I have no idea.
var client = new GraphClient(new Uri("http://localhost:7474/db/data"));
client.Connect();
client.Create(new User { Id = 1, Username = "joe" }, new UserBelongsTo(client.RootNode));
client.Create(new User { Id = 2, Username = "cloe" }, new UserBelongsTo(client.RootNode));
client.Create(new Activity { Id = 1, Name = "Bocce Ball" }, new ActivityBelongsTo(client.RootNode));
client.Create(new Activity { Id = 2, Name = "Programming" }, new ActivityBelongsTo(client.RootNode));
var user = client.RootNode.In<User>(UserBelongsTo.TypeKey, u=>u.Id == 1).SingleOrDefault();
var activity = client.RootNode.In<Activity>(ActivityBelongsTo.TypeKey, a=>a.Id == 1).SingleOrDefault();
client.CreateRelationship(user.Reference, new Plays(activity.Reference));
user = client.RootNode.In<User>(UserBelongsTo.TypeKey, u => u.Id == 1).SingleOrDefault();
activity = client.RootNode.In<Activity>(ActivityBelongsTo.TypeKey, a => a.Id == 1).SingleOrDefault();
I'm just getting started too. I would suggest you check out this blog:
http://romikoderbynew.com/2011/07/30/neo4jclient-primer/
Also, check http://frictionfree.org and its source code (in the about section) for more examples.
Creating relationships on existing - as I understand, this is possible. However, it appears to be easier to associate nodes as you create them. From the blog:
You can also create relationships between existing nodes.
graphClient.CreateRelationship(customerNodeReference, new
Speaks(languageNode.Reference));
RootNode - I believe you need to start a query from a node, I don't think you can do a
SELECT * FROM ... WHERE
Therefore, it would make sense that you need to attach nodes to the root node. This is an example from the FrictionFreeApp:
var node = graphClient.Create(
user,
new UserBelongsTo(rootNode));