I'm just starting to learn the Cypher query language and GraphDb in general. I've created some indexes using the class name of my nodes like:
"com.acme.node.SomeNodeType"
I can't for the life of me figure out how to reference this index in Cypher. I found this thread but using ` didn't work for me.
So I guess I have 2 questions:
Is it possible to use an index with dots in the name?
If so, how do I specify the name in the query?
can you try to query them with '' like
start n = node:`my.index`('name:test') return n
?
Related
I must create a set of relationships, all having the same source and type, like in the following sample:
create (_1)-[:`typ`]->(:`x` {`name`:"Mark"})
create (_1)-[:`typ`]->(:`y` {`name`:"Jane"})
create (_1)-[:`typ`]->(:`z` {`name`:"John"})
...
I'd like to have a shorten way to write those statements, like following attempt?
create (_1)-[:`typ`]->[(:`x` {`name`:"Mark"}),
(:`y` {`name`:"Jane"}),
(:`z` {`name`:"John"})]
Any idea?
Thank you in advance.
Paolo
You could do it in a performant and easy way by this pattern:
{batch: [
{from:"alice#example.com",to:"bob#example.com",properties:{since:2012}},
{from:"alice#example.com",to:"charlie#example.com",properties:{since:2016}}]}
UNWIND {batch} as row
MATCH (from:Label {row.from})
MATCH (to:Label {row.to})
CREATE/MERGE (from)-[rel:KNOWS]->(to)
(ON CREATE) SET rel += row.properties
Taken with thanks from 5 Tips & Tricks for Fast Batched Updates of Graph Structures with Neo4j and Cypher by #MichaelHunger.
I want to create a friends relation between abcd node and vbnm node having same node-name - Student
neo4j graph database visualization
I execute the following query, It doesn't show me any error but this query doesn't create any relation
match(Student:Stu),(Student:Stu)where Student.name="abcd" AND Student.name="vbnm" create(Student)-[fr:friends]->(Student)
You need use different variable name:
match(Student1:Stu),(Student2:Stu)
where Student1.name="abcd" AND
Student2.name="vbnm"
create(Student1)-[fr:friends]->(Student2)
I think you are confused by the syntax a little bit. Let me give you an example of a MATCH query syntax.
MATCH (variable1:Label),(variable2:Label) where variable1.foo = variable2.foo
You mixed label and variable in your query and each entity should have its own variable (variable1 and variable2) so you can interact with them.
So in your case the optimal query looks something like:
MATCH (s1:Student),(s2:Student ) where s1.name="abcd" AND s2.name="vbnm"
CREATE (s1)-[:friends]->(s2)
Note that you do not need to assign a variable to [:friends] relationship as you do not interact with it later in the same query.
I mean, if I have two indexes:
CREATE INDEX ON :labelA(idA)
CREATE INDEX ON :labelB(idB)
And I do the following query:
MATCH (n:labelA {idA: valA})
MATCH (n:labelB {idB: valB})
CREATE (n)-[:Rel]->(B)
Does neo4j just use one of the indexes? If does, How do I force neo4j to use the 2 indexes?.
Thanks in advance.
Currently Neo will only use a maximum of one index to determine where to start walking the graph as part of query resolution. This is likely to change in the future. You can give Neo hints on which of the 2 or more indexes to use via USE INDEX but you can't get it to use more than one at this point.
You could check if indexes are being used to find the nodes by prepending your query with PROFILE.
You could throw the query optimizer a hint something like this...
MATCH (a:labelA {idA: valA}), (b:labelB {idB: valB})
USING INDEX a:LabelA(idA)
USING INDEX b:LabelB(idB)
CREATE (a)-[:Rel]->(b)
I'd like to make a cypher query that generates a specific json output. Part of this output includes an object with a dynamic amount of keys relative to the children of a parent node:
{
...
"parent_keystring" : {
child_node_one.name : child_node_one.foo
child_node_two.name : child_node_two.foo
child_node_three.name : child_node_three.foo
child_node_four.name : child_node_four.foo
child_node_five.name : child_node_five.foo
}
}
I've tried to create a cypher query but I do not believe I am close to achieving the desired output mentioned above:
MATCH (n)-[relone:SPECIFIC_RELATIONSHIP]->(child_node)
WHERE n.id='839930493049039430'
RETURN n.id AS id,
n.name AS name,
labels(n)[0] AS type,
{
COLLECT({
child.name : children.foo
}) AS rel_two_representation
} AS parent_keystring
I had planned for children.foo to be a count of how many occurrences of each particular relationship/child of the parent. Is there a way to make use of the reduce function? Where a report would generate based on analyzing the array proposed below? ie report would be a json object where each key is a distinct RELATIONSHIP and the property value would be the amount of times that relationship stems from the parent node?
Thank you greatly in advance for guidance you can offer.
I'm not sure that Cypher will let you use a variable to determine an object's key. Would using an Array work for you?
COLLECT([child.name, children.foo]) AS rel_two_representation
I think, Neo4j Server API output by itself should be considered as any database output (like MySQL). Even if it is possible to achieve, with default functionality, desired output - it is not natural way for database.
Probably you should look into creating your own server plugin. This allows you to implement any custom logic, with desired output.
I have imported freebase dump to neo4j. But currently i am facing issue with get queries because of size of db. While import i just created node index and indexed URI property to index for each node. For each node i am adding multiple properties like label_en, type_content_type_en.
props.put(URI_PROPERTY, subject.stringValue());
Long subjectNode = db.createNode(props);
tmpIndex.put(subject.stringValue(), subjectNode);
nodeIndex.add(subjectNode, props);
Now my cypher queries are like this. Which are timing out. I am unable to add index on label_en property. Can anybody help?
match (n)-[r*0..1]->(a) where n.label_en=~'Hibernate.*' return n, a
Update
BatchInserter db = BatchInserters.inserter("ttl.db", config);
BatchInserterIndexProvider indexProvider = new LuceneBatchInserterIndexProvider(db);
BatchInserterIndex index = indexProvider.nodeIndex("ttlIndex", MapUtil.stringMap("type", "exact"));
Question: When i have added node in nodeindex i have added with property URI
props.put(URI_PROPERTY, subject.stringValue());
Long subjectNode = db.createNode(props);
nodeIndex.add(subjectNode, props);
Later in code i have added another property to node(Named as label_en). But I have not added or updated nodeindex. So as per my understanding lucene does not have label_en property indexed. My graph is already built so i am trying to add index on label_en property of my node because my query is on label_en.
Your code sample is missing how you created your index. But I'm pretty sure what you're doing is using a legacy index, which is based on Apache Lucene.
Your Cypher query is using the regex operator =~. That's not how you use a legacy index; this seems to be forcing cypher to ignore the legacy index, and have the java layer run that regex on every possible value of the label_en property.
Instead, with Cypher you should use a START clause and use the legacy indexing query language.
For you, that would look something like this:
START n=node:my_index_name("label_en:Hibernate.*")
MATCH (n)-[r*0..1]->(a)
RETURN n, a;
Notice the string label_en:Hibernate.* - that's a Lucene query string that says to check that property name for that particular string. Cypher/neo4j is not interpreting that; it's passing it through to Lucene.
Your code didn't provide the name of your index. You'll have to change my_index_name above to whatever you named it when you created the legacy index.