This is quite a general question but to make it more understandable I'll give it a bit of context.
In neo4j I have a series of words (nodes) that are associated with one another. I want to specify a list of nodes and the Cypher query return a list of any relationships between those nodes.
The nodes specified in the list are all guaranteed to have at least one relationship to another node specified in the list.
I created a query to do this and in certain circumstances it works fine - http://console.neo4j.org/?id=s30cbm
Unfortunately, when I add the words 'bark' and 'dog' to the list I get an 'unexpected traversal state encountered' error message. I presume this is because the database cursor has got to the fruit node and then there's no relationship between that and bark, even though there is a relationship from tree to bark. http://console.neo4j.org/?id=258d6g
I'm obviously doing the query slightly wrong and any advice would be appreciated on how I can rectify this.
This works in the latest console (your second link), btw, so it looks like they fixed it. Looks like it should be working in 1.9-M04+.
Related
I am working on Panama dataset using Neo4J graph database 1.1.5 web version. I identified Ion Sturza, former Prime Minister of Moldova on the database and want to make a map of his related network. I used following code to query using Cypher (creating a variable 'IonSturza'):
MATCH (IonSturza {name: "Ion Sturza"}) RETURN IonSturza
I identified that the entity 'CONSTANTIN LUTSENKO' linked differently to entities like 'Quade..' and 'Kinbo...' with a name in small letters as in this picture. I hence want to map a relationship 'SAME_COMPANY_AS' between the capslock and the uncapped version. I tried the following code based on this answer by #StefanArmbruster:
MATCH (a:Officer {name :"Constantin Lutsenko"}),(b:Officer{name :
"CONSTANTIN LUTSENKO"})
where (a:Officer{name :"Constantin Lutsenko"})-[:SHAREHOLDER_OF]->
(b:Entity{id:'284429'})
CREATE (a)-[:SAME_COMPANY_AS]->(b)
Instead of indexing, I used the 'where' statement to specify the uncapped version which is linked only to the entity bearing id '284429'.
My code however shows the cartesian product error message:
This query builds a cartesian product between disconnected patterns.If a part of a query contains multiple disconnected patterns, this will build a cartesian product between all those parts. This may produce a large amount of data and slow down query processing. While occasionally intended, it may often be possible to reformulate the query that avoids the use of this cross product, perhaps by adding a relationship between the different parts or by using OPTIONAL MATCH (identifier is: (b))<<
Also when I execute, there are no changes, no rows!! What am I missing here? Can someone please help me with inserting this relationship between the nodes. Thanks in advance!
The cartesian product warning will appear whenever you're matching on two or more disconnected patterns. In this case, however, it's fine, because you're looking up both of them by what is likely a unique name, s your result should be one node each.
If each separate part of that pattern returned multiple nodes, then you would have (rows of a) x (rows of b), a cartesian product between the two result sets.
So in this particular case, don't mind the warning.
As for why you're not seeing changes, note that you're reusing variables for different parts of the graph: you're using variable b for both the uppercase version of the officer, and for the :Entity in your WHERE. There is no node that matches to both.
Instead, use different variables for each, and include the :Entity in your match. Also, once you match to nodes and bind them to variables, you can reuse the variable names later in your query without having to repeat its labels or properties.
Try this:
MATCH (a:Officer {name :"Constantin Lutsenko"})-[:SHAREHOLDER_OF]->
(:Entity{id:'284429'}),(b:Officer{name : "CONSTANTIN LUTSENKO"})
CREATE (a)-[:SAME_COMPANY_AS]->(b)
Though I'm not quite sure of what you're trying to do...is an :Officer a company? That relationship type doesn't quite seem right.
I tried the answer by #InverseFalcon and thanks to it, by modifying the property identifier from 'id' to 'name' and using the property for both 'a' and 'b', 4 relationships were created by the following code:
MATCH (a:Officer {name :"Constantin Lutsenko"})-[:SHAREHOLDER_OF]->
(:Entity{name:'KINBOROUGH PORTFOLIO LTD.'}),(b:Officer{name : "CONSTANTIN
LUTSENKO"})-[:SHAREHOLDER_OF]->(:Entity{name:'Chandler Group Holdings Ltd'})
CREATE (a)-[:SAME_NAME_AS]->(b)
Thank you so much #InverseFalcon!
I was learning neo4j, and following the tutorial provide atsearching for relationship.
I followed it, added two nodes and a relationship between them. I did exactly according to the tutorial in above link. But when i try to display the relationship i just added, by the following
MATCH (e)-[r:DO_SHOPPING_WITH ]->(cc)
RETURN r
it showed nothing.
to make sure, I displayed all nodes by
MATCH (a) return a
and it showed 2 nodes and the relationship between them.
Not only this case, I tried later examples, by similar search for relationship all are showed empty.
could anyone explain why I cannot display the relationship as it is told in the tutorial?
Pretty simple example, but somehow not working.
Please help!
It sounds like you're just talking about the graph result view. When the only items returned from a query are relationships, they won't show up, as it requires the nodes on either side of a relationship to be returned in order to display.
While this is current behavior, past behavior was able to display the start and end nodes of a relationship even if just relationships were returned, and it's not a bad idea to consider reverting to this previous behavior.
I think this issue on the browser project is related.
When writing a query to add relationships to existing nodes, it keeps me warning with this message:
"This query builds a cartesian product between disconnected patterns.
If a part of a query contains multiple disconnected patterns, this will build a cartesian product between all those parts. This may produce a large amount of data and slow down query processing. While occasionally intended, it may often be possible to reformulate the query that avoids the use of this cross product, perhaps by adding a relationship between the different parts or by using OPTIONAL MATCH (identifier is: (e))"
If I run the query, it creates no relationships.
The query is:
match
(a{name:"Angela"}),
(b{name:"Carlo"}),
(c{name:"Andrea"}),
(d{name:"Patrizia"}),
(e{name:"Paolo"}),
(f{name:"Roberta"}),
(g{name:"Marco"}),
(h{name:"Susanna"}),
(i{name:"Laura"}),
(l{name:"Giuseppe"})
create
(a)-[:mother]->(b),
(a)-[:grandmother]->(c), (e)-[:grandfather]->(c), (i)-[:grandfather]->(c), (l)-[:grandmother]->(c),
(b)-[:father]->(c),
(e)-[:father]->(b),
(l)-[:father]->(d),
(i)-[:mother]->(d),
(d)-[:mother]->(c),
(c)-[:boyfriend]->(f),
(g)-[:brother]->(f),
(g)-[:brother]->(h),
(f)-[:sister]->(g), (f)-[:sister]->(h)
Can anyone help me?
PS: if I run the same query, but with just one or two relationships (and less nodes in the match clause), it creates the relationships correctly.
What is wrong here?
First of all, as I mentionned in my comments, you don't have any Labels, it's a really bad practice because Labels are useful to match properties in a certains dataset (if you match "name" property, you don't want to match it on a node who doesn't have a name, Labels are here for that.
The second problem is that your query doesn't know how many nodes it will get before it does. It means that if you have 500 000 nodes having name : "Angela" and 500 000 nodes having name : "Carlo", you will create one relation from each Angela node, going on each Carlo, that's quite a big query (500 000 * 500 000 relations to create if my maths aren't bad). Cypher is giving you a warning for that.
Cypher will still tell you this warning because you aren't using Unique properties to match your nodes, even with Labels, you will still have the warning.
Solution?
Use unique properties to create and match your nodes, so you avoid cartesian product.
Always use labels, Neo4j without labels is like using one giant table in SQL to store all of your data.
If you want to know how your query will run, use PROFILE before your query, here is the profile plan for your query:
Does every single one of those name strings exist? If not then you're not going to get any results because it's all one big match. You could try changing it to a MERGE.
But Supamiu is right, you really should have a label (say Person) and an index on :Person(name).
I'm brand new to Cypher (and Stackoverflow) and am having trouble creating relationships between nodes based on share property keys.
I would like to do something like this:
MATCH (a:Person)-->()<--(b:Country)
WHERE HAS (a.id) AND HAS (b.id) AND a.id=b.id
CREATE (a)-[:LIVES]->(b);
to create a relationship between Country node and Person nodes where they share the same id.
The above creates no errors when run but doesn't create any relationships either and I know that the ids should match.
Many thanks!!
EDIT:
I think I know what is going wrong - I'm asking to match nodes that have a relationship to eachother but no relationships are set up yet hence 0 results. I have now tried:
MATCH (a:Person),
(b:Country)
WHERE HAS (a.id) AND HAS (b.id) AND a.id=b.id
CREATE (a)-[:LIVES]->(b);
and the query is running. It's a big data set so might take a while......
That worked. Had to reduce the size of my data set (down from 64k nodes) as Neo4j was taking way too long to process but once I had a smaller set it worked fine.
One minor addition for future Googlers.
per the help files as of version 3.4
The has() function has been superseded by exists() and has been removed.
The new code should read
MATCH (a:Person),
(b:Country)
WHERE EXISTS (a.id) AND EXISTS (b.id) AND a.id=b.id
CREATE (a)-[:LIVES]->(b);
My graph is composed of multiple "sub-graphes" that are disconnected from one another. These sub-graphes are composed of nodes that are connected with a given relation type.
I would like to get (for example) the list of sub-graphes that contain at least one node that has the property "name" equals "John".
It's equivalent to finding one node per subgraph having this property.
One solution would be to find all the nodes having this property and loop through this list to only pick the ones that are not connected to the previously picked ones. But that would be ugly and quite heavy. Is there an elegant way to do that with Cypher?
I'm trying with something along this direction but have no success so far:
START source=node:user('name:"John"')
MATCH source-[r?:KNOWS*]-target
WHERE r is null
RETURN source
Try this one it may help
START source=node:user('name:"John"')
MATCH source-[r:KNOWS]-()-[r2:KNOWS]-target
WHERE NOT(source-[r:KNOWS]-target)
RETURN target