I am using neo4j with people and companies as nodes and friend_of/works_at relationship between these.
I would like to know how to implement a get introduced to a second degree connection that linked in uses. The idea is to get your second degree connections at the company you wish to apply. If there are these second degree connections, then you would like to know who among your 1st deg connections can introduce y*ou to these 2nd deg connections.
For this I'm trying this query :
START from = node:Nodes(startNode), company = node:Nodes(endNode)
MATCH from-[:FRIEND_OF]->f-[:FRIEND_OF]-fof-[:WORKS_AT]->company
WHERE not(fof = from) and not (from-[:FRIEND_OF]->fof)
RETURN distinct f.name, fof.name, company.name
But, this returns duplicate friend of friend names (fof.name), since the distinct is applied on all the parameters that are returned as a whole. It could be like I have friends X and Y who are both connected to Z who works at company C. This way, I get both X-Z-C and Y-Z-C. But, I want to apply distinct on Z, such that I get either X-Z-C or Y-Z-C or maybe a list/collection/aggregate of all friends that connect to Z. This could like ["X","Y"..]->Z How should I modify my query?
http://console.neo4j.org/?id=s1m14g
start joe=node:node_auto_index(name = "Joe")
match joe-[:knows]->friend-[:knows]->friend_of_friend
where not(joe-[:knows]-friend_of_friend)
return collect(friend.name), friend_of_friend.name
Related
I'm investigating the use of Neo4j to detect potentially fraudulent card transactions in near real time. I receive details of a customer and a card they've just used from our on-line systems. What I'm trying to do here is create new nodes for the customer and card if they don't exist, then establish the relationship between them.
Whenever the customer uses the card I want to set the time the card was last used, in addition, if this is the first time this customer-->card relationship has been seen, update totals of the number of cards the customer is associated with and the number of customers associated with the card.
The Cypher below seems to work, however I think it will re-evaluate the counts every time the relationship is seen, not just on the create. Is it possible to use the ON MATCH and ON CREATE in this statement to limit the unnecessary processing?
MERGE (c:customers {customer_id:"12345678"})
MERGE (a:cards {card_hash:"45uIic..."})
MERGE (c)-[r:has_card]->(a)
set r.last_transaction = "30-NOV-2016 07:58:42"
set a.card_ct = size(()-[:has_card]->(a))
set c.card_count = size((c)-[:has_card]->())
I'm running this from Python (using py2neo), I also want to return something back that will allow me to kick off a bespoke dijkstra based search of the neighborhood. Any ideas how I'd return some variable based on whether this was a new or existing relationship?
There is no need you to even have the card_ct or card_count properties.
Since neo4j 2.1, getting a count of the number of relationships of a specific type from a node is very efficient. So, every time you need a count, just use SIZE(()-[:has_card]->(node)) or SIZE((node)-[:has_card]->()).
How about something like this. Create a counter on a MATCH and if the counter is greater than zero then it is an existing relationship. Otherwise it is a new relationship.
MERGE (c:customers {customer_id:"12345678"})
MERGE (a:cards {card_hash:"45uIic..."})
MERGE (c)-[r:has_card]->(a)
ON MATCH SET r.num = coalesce(r.num, 0) + 1
set r.last_transaction = "30-NOV-2016 07:58:42"
set a.card_ct = size(()-[:has_card]->(a))
set c.card_count = size((c)-[:has_card]->())
RETURN
CASE
WHEN r.num > 0 THEN false
ELSE true
END as new_relationship
Here's the Cypher I've ended up with, thanks to Dave Bennett for his suggestion. I also realised that I don't need to initiate any further analysis if only 1 customer is associated with 1 card so I've excluded this as well.
MERGE (c:customers {customer_id:"12345678"})
MERGE (a:cards {card_hash:"BFgn..."})
MERGE (c)-[r:has_card]->(a)
ON CREATE SET a.card_scheme = "VISA DEBIT"
, a.card_ct = size(()-[:has_card]->(a))
, c.card_count = size((c)-[:has_card]->())
ON MATCH SET r.ind = 1
SET r.last_transaction = "06-Dec-2016 11:19:13"
RETURN CASE WHEN exists(r.ind)
AND a.card_ct + c.card_count > 2
THEN false
ELSE true END as new_relationship
Good morning,
I want to build a structure in Neo4J where I can handle my users and groups (kind of ACL). The idea is to have for each user and for each group a node with all the details. The groups shall become a graph where a root group will have sub-groups that can have also sub-groups without limit. The relation will be -[:IS_SUBGROUP_OF]- - so far nothing exciting. Every user will be related to a group with -[:IS_MEMBER_OF]- to have a clear assignment. Of course a user can be a member of 1 or more groups. Some users will have a different relation like -[:IS_LEADER_OF]- to identify teamlead of the groups.
My tasks:
Assignment: I can query each member of a group with a simple query, I can even query members of the subgroups using the current logged in and asking user:
MATCH (d1:Group:Local) -- (c:User)
MATCH (d:User) -[:IS_MEMBER_OF|IS_LEADER_OF]- (g:Group:Local)-[:IS_SUBGROUP_OF*0..]->(d1)
WHERE c.login = userLogin
RETURN DISTINCT d.lastname, d.firstname
I get every related user to every group of the current user and below (subgroups). Maybe you have a hint how I cna improve the query or the model.
Approval
Here I am stucked as I want to have all users of the current group from the querying user and all members of all subgroups - except the leader of the current group. The reason behind is that a teamlead shall not be able to approve actions for himself but though for every other member of his group and all members of subgroups including their teamleads.
I tried to use the relations -[:IS_LEADER_OF]- to exclude them but than I loose also the teamleads of the subgroups. Does anyone has an idea how I would either change the model or how I can query the graph to get all users except the teamlead of the current group?
Thanks for your time,
Balael
* EDIT *
I think I am getting close, I just need to understand the results of those both queries:
MATCH (d:User) -- (g:Group) WHERE g.uuid = "xx"
RETURN d.lastname, d.firstname
Returns all user in this group no matter what relationship (leader / member)
MATCH (d:User) -- (g:Group), (g)--(c:User{uuid:"yy"})
RETURN d.lastname, d.firstname
Returns all user of that group except the user c. I would have expected to get c as well in the list with d-users as c is part of that group and should be found with (d:User).
I do not understand the difference between both queries, maybe someone has a hint for me?
You can simplify your query slightly (however this should not have an impact on performance):
MATCH (d:User) -[:IS_MEMBER_OF|IS_LEADER_OF]- (g:Group:Local)-[:IS_SUBGROUP_OF*0..]->(d1:Group:Local)--(c:User{login:"userlogin"})
RETURN DISTINCT d.lastname, d.firstname
Don't completely understand your question, but I assume you want to make sure that d1 and c are not connected by a IS_LEADER_OF relationship. If so, try:
MATCH (d:User) -[:IS_MEMBER_OF|IS_LEADER_OF]- (g:Group:Local)-[:IS_SUBGROUP_OF*0..]->(d1:Group:Local)-[r]-(c:User{login:"userlogin"})
WHERE type(r)<>'IS_LEADER_OF'
RETURN DISTINCT d.lastname, d.firstname
following up on * EDIT * in the question
In a MATCH you specify a path. By definition a path does not use the same relationship twice. Otherwise there is a danger to run into infinite recursion. Looking at the second query in the "EDIT" section above: the right part matches yy's relationship to the group whereas the left part matches all user related to this group. To prevent multiple usage of the same relationship the left part does not hit use yy
I'm currently developing some kind of a configurator using neo4j as a backend. Now I ran into a problem, I don't know how to solve best.
I've got nodes created like this:
(A:Product {name:'ProductA', minWidth:20, maxWidth:200, minHeight:10, maxHeight:400})
(B:Product {name:'ProductB', minWidth:40, maxWidth:100, minHeight:20, maxHeight:300})
...
There is an interface where the user can input a desired width & height, f.e. Width=30, Height=250. Now I'd like to check which products match the input criteria. As the input might be any long value, the approach used in http://neo4j.com/blog/modeling-a-multilevel-index-in-neoj4/ with dates doesn't seem to be suitable for me. How can I run a cypher query giving me all the nodes matching the input criteria?
I don't know if I understand well what you are asking for, but if I do, here a simple query to get this:
Assuming the user wants width = 30 and height = 50
Match (p:Product)
WHERE
p.minWidth < 30 AND p.maxWidth > 30 AND
p.minHeight < 50 AND p.maxHeight > 50
RETURN
p
If this is not what you are looking for, feel free to say it as comment.
I have a graph in which I am keeping the degree of a node as a property called "degree" in the node.
What I need is when I create an edge between two nodes, I need to increment the degree of the two nodes.
For creating unique edges I am using "CREATE UNIQUE" for the edges. So if I need to increment the property "degree" of the corresponding nodes, I need to use "ON CREATE" and "ON MATCH" as it is for "MERGE".
But I can't use the ON CREATE and ON MATCH with CREATE UNIQUE. So whats the proper way of using ON CREATE and ON MATCH with CREATE UNIQUE?
This is the way I am trying:
MATCH (n1:PER {Node_Id:"X"}), (n2:PER {Node_Id:"Y"}) WHERE n1.Node_Id<>n2.Node_Id CREATE UNIQUE (n1)-[r:PER_PER {Doc_Id:"st_new", Event_Class:"EC_1", Event_Instance:"EI_1"}]-(n2) ON CREATE SET n1.degree = n1.degree + 1, n2.degree = n2.degree + 1
Not sure why you want to store the degree as a property. Neo4j has a getDegree() function on API level, see http://neo4j.com/docs/stable/javadocs/org/neo4j/graphdb/Node.html#getDegree(). Cypher is not yet using this everywhere possible but for some patterns it already does.
Nevertheless to answer your question: just use MERGE instead of CREATE UNIQUE for eventually establishing the relationship:
MATCH (n1:PER {Node_Id:"X"}), (n2:PER {Node_Id:"Y"})
WHERE n1.Node_Id<>n2.Node_Id
MERGE (n1)-[r:PER_PER {Doc_Id:"st_new", Event_Class:"EC_1", Event_Instance:"EI_1"}]-(n2)
ON CREATE SET n1.degree = n1.degree + 1, n2.degree = n2.degree + 1
If you do have a good reason to store node degrees as a property, please have a look at one of our modules called RelCount, which has been build exactly for what you need to do. It is described in detail in my thesis.
However, as Stefan points out, have a go with getDegree() first and only if that isn't fast enough, or you need to get degree based on some relationship property values as well, use RelCount.
Does it possible to have an order by "property" with a where clause and now the "index/position" of the result?
I mean, when using order for sorting we need to be able to know the position of the result in the sort.
Imagine a scoreboard with 1 million user node, i do an order by on user node.score with a where "name = user_name" and i wan't to know the current rank of the user. I do not find how to do this using order by ...
start game=node(1)
match game-[:has_child_user]->user
with user
order by user.score
with user
where user.name = "my_user"
return user , "the position in the sort";
the expected result would be :
node_user | rank
(i don't want to fetch one million entries at client side to know the current rank/position of a node in the ORDER BY!)
This functionality does not exist today in Cypher. Do you have an example of what this would look like in SQL? Would the below be something that fits the bill? (just a sketch, not working!)
(your code)
start game=node(1)
match game-[:has_child_user]->user
with user
order by user.score
(+ this code)
with user, index() as rank
return user.name, rank;
If you have more thoughts or want to start hacking on this please open an issue at https://github.com/neo4j/neo4j/issues
For the time being there is a work around that you can do:
start n=node(0),rank_node=node(1)
match n-[r:rank]->rn
where rn.score <= rank_node.score
return rank_node,count(*) as pos;
For live example see: http://console.neo4j.org/?id=bela20