I am new to Neo4J and struggling to get the output I need without extra external processing. I am pretty sure that Neo4J is easily capable of doing that. Please advice on best approach.
I have a 2 types of nodes: Ingredient and Function that are connected using relation that has property of {Weight: 1}. I am querying a list of ingredients and I want to get a sum of connections multiplied by weight of each connection leading to each distinct function.
Here's what I came up with.
MATCH (q:Ingredient)-[r]->(p) WHERE q.RefNo IN [1,2,3] RETURN r,p
This produces following output
{"weight":1}│{"Function":"X1"}
{"weight":0.5}│{"Function":"X1"}
{"weight":0.7}│{"Function":"X2"}
{"weight":0.4}│{"Function":"X3"}
{"weight":0.5}│{"Function":"X4"}
What I want to get in a single/stacked query is
X1:1.5, X2:1=0.7, X3:0.4, X4:0.5
Please advice on possible solution of this problem.
Almost there, you just need to use an aggregation function (in this case, sum()) on the weight, and the Function property as your non-aggregation column:
MATCH (q:Ingredient)-[r]->(p)
WHERE q.RefNo IN [1,2,3]
RETURN p.Function, sum(r.weight) as weight
Or if you only want a single row result:
MATCH (q:Ingredient)-[r]->(p)
WHERE q.RefNo IN [1,2,3]
WITH p, sum(r.weight) as weight
RETURN collect(p {.Function, weight}) as functionWeights
Related
I need 2 lists of nodes for the call of my procedure. The following query doesnt work because the first list is not defined (overwritten with the second collect I guess). I already tried a lot of queries but somehow im missing the right one. I think this one is showing what I actually want to achieve.
MATCH (n:NODE)
WHERE n.NODE_ELID='BLOCK1' OR n.NODE_ELID='BLOCK2'
WITH COLLECT(n) AS blockNodes
MATCH (m:NODE)
WHERE m.NODE_ELID='MUST1' OR m.NODE_ELID='MUST2'
WITH COLLECT(m) AS mustNodes
MATCH (from:NODE{NODE_ELID:'START'}),(to:NODE{NODE_ELID:'END'})
CALL example.aStar(from,to,'CONNECTED_TO','DISTANCE','COORD_X','COORD_Y',blockNodes,mustNodes) yield path as path, weight as weight
RETURN path, weight
Thanks in advance.
Pass along blockNodes in line 6:
WITH blockNodes, COLLECT(m) AS mustNodes
The point here is that WITH does many things: it performs projection, aggregation, filtering (as WITH clauses can have their own WHERE clause) and ordering/limiting. See the docs on WITH for more details.
I am new at Neo4j but not to graphs and I have a specific problem I did not manage to solve with Cypher.
With this type of data:
I would like to be able in a single query to follow some incoming and some outgoing flow.
Example:
Starting on "source"
Follow all "A" relationships in the outgoing way
Follow all "B" relationships in the incoming way
My problem is that Cypher only allows one single direction to be specified in the relationship pattern.
So I could do (source)-[:A|:B*]->() or (source)<-[:A|:B*]-().
But I have no possibility to tell Cypher that I want to follow -[:A]-> and <-[:B]-.
By the way, I know that I could do -[:A|:B]- but this won't solve my problem because I don't want to follow -[:B]-> and <-[:A]-.
Thanks in advance for your help :)
Alternatively to #Gabor Szarnyas answer, I think you can achieve your goal using the APOC procedure apoc.path.expand.
Using this sample data set:
CREATE (:Source)-[:A]->()-[:A]->()<-[:B]-()-[:A]->()
And calling apoc.path.expand:
match (source:Source)
call apoc.path.expand(source,"A>|<B","",0,5) yield path
return path
You will get this path as output:
The apoc.path.expand call starts from the source node following -[:A]-> and <-[:B]- relationships.
Remember to install APOC procedures according to the version of Neo4j you are using. Take a look in the version compatibility matrix.
To express this in a single query would require a regular path query, which has been proposed to and accepted to openCypher, but it is not yet implemented.
I see two possible workarounds. I recreated your example with this command with a Source label for the source node:
CREATE (:Source)-[:A]->()-[:A]->()<-[:B]-()-[:A]->()
(1) Insert additional relationships that have the same direction:
MATCH (s)-[:B]->(t)
CREATE (s)<-[:B2]-(t)
And use this relationship for traversal:
MATCH p=(source)-[:A|:B2*]->()
RETURN p
(2) As you mentioned:
By the way, I know that I could do -[:A|:B]- but this won't solve my problem because I don't want to follow -[:B]-> and <-[:A]-.
You could use this approach to first get potential path candidates and manually check the directions of the relationships afterwards. Of course, this is an expensive operation but you only have to calculate it on the candidates, a possibly small data set.
MATCH p=(source:Source)-[:A|:B*]-()
WITH p, nodes(p) AS nodes, relationships(p) AS rels
WHERE all(i IN range(0, size(rels) - 1) WHERE
CASE type(rels[i])
WHEN 'A' THEN startNode(rels[i]) = nodes[i]
ELSE /* B */ startNode(rels[i]) = nodes[i+1]
END)
RETURN p
Let's break down how this works:
We store path candidates in p and use the nodes and relationships functions to extract the lists of nodes/relationships from it.
We define a range of indexes for the relationships (e.g. from 0, 1, 2 if there are 3 relationships).
To determine the direction of relationships, we use the startNode function. For example, if there is a relationship r between nodes n1 to n2, the paths will like <n1, r, n2>. If r was traversed to in the outgoing direction, the startNode(r) will return n1, if it was traverse in the incoming direction, startNode(r) will return n2. The type of the relationship is checked with the type function and a simple CASE expression is used to differentiate between types.
The WHERE clause uses the all predicate function to check whether all :A and :B relationships had the appropriate directions.
I have some questions regarding Neo4j's Query profiling.
Consider below simple Cypher query:
PROFILE
MATCH (n:Consumer {mobileNumber: "yyyyyyyyy"}),
(m:Consumer {mobileNumber: "xxxxxxxxxxx"})
WITH n,m
MATCH (n)-[r:HAS_CONTACT]->(m)
RETURN n,m,r;
and output is:
So according to Neo4j's Documentation:
3.7.2.2. Expand Into
When both the start and end node have already been found, expand-into
is used to find all connecting relationships between the two nodes.
Query.
MATCH (p:Person { name: 'me' })-[:FRIENDS_WITH]->(fof)-->(p) RETURN
> fof
So here in the above query (in my case), first of all, it should find both the StartNode & the EndNode before finding any relationships. But unfortunately, it's just finding the StartNode, and then going to expand all connected :HAS_CONTACT relationships, which results in not using "Expand Into" operator. Why does this work this way? There is only one :HAS_CONTACT relationship between the two nodes. There is a Unique Index constraint on :Consumer{mobileNumber}. Why does the above query expand all 7 relationships?
Another question is about the Filter operator: why does it requires 12 db hits although all nodes/ relationships are already retrieved? Why does this operation require 12 db calls for just 6 rows?
Edited
This is the complete Graph I am querying:
Also I have tested different versions of same above query, but the same Query Profile result is returned:
1
PROFILE
MATCH (n:Consumer{mobileNumber: "yyyyyyyyy"})
MATCH (m:Consumer{mobileNumber: "xxxxxxxxxxx"})
WITH n,m
MATCH (n)-[r:HAS_CONTACT]->(m)
RETURN n,m,r;
2
PROFILE
MATCH (n:Consumer{mobileNumber: "yyyyyyyyy"}), (m:Consumer{mobileNumber: "xxxxxxxxxxx"})
WITH n,m
MATCH (n)-[r:HAS_CONTACT]->(m)
RETURN n,m,r;
3
PROFILE
MATCH (n:Consumer{mobileNumber: "yyyyyyyyy"})
WITH n
MATCH (n)-[r:HAS_CONTACT]->(m:Consumer{mobileNumber: "xxxxxxxxxxx"})
RETURN n,m,r;
The query you are executing and the example provided in the Neo4j documentation for Expand Into are not the same. The example query starts and ends at the same node.
If you want the planner to find both nodes first and see if there is a relationship then you could use shortestPath with a length of 1 to minimize the DB hits.
PROFILE
MATCH (n:Consumer {mobileNumber: "yyyyyyyyy"}),
(m:Consumer {mobileNumber: "xxxxxxxxxxx"})
WITH n,m
MATCH Path=shortestPath((n)-[r:HAS_CONTACT*1]->(m))
RETURN n,m,r;
Why does this do this?
It appears that this behaviour relates to how the query planner performs a database search in response to your cypher query. Cypher provides an interface to search and perform operations in the graph (alternatives include the Java API, etc.), queries are handled by the query planner and then turned into graph operations by neo4j's internals. It make sense that the query planner will find what is likely to be the most efficient way to search the graph (hence why we love neo), and so just because a cypher query is written one way, it won't necessarily search the graph in the way we imagine it will in our head.
The documentation on this seemed a little sparse (or, rather I couldn't find it properly), any links or further explanations would be much appreciated.
Examining your query, I think you're trying to say this:
"Find two nodes each with a :Consumer label, n and m, with contact numbers x and y respectively, using the mobileNumber index. If you find them, try and find a -[:HAS_CONTACT]-> relationship from n to m. If you find the relationship, return both nodes and the relationship, else return nothing."
Running this query in this way requires a cartesian product to be created (i.e., a little table of all combinations of n and m - in this case only one row - but for other queries potentially many more), and then relationships to be searched for between each of these rows.
Rather than doing that, since a MATCH clause must be met in order to continue with the query, neo knows that the two nodes n and m must be connected via the -[:HAS_CONTACT]-> relationship if the query is to return anything. Thus, the most efficient way to run the query (and avoid the cartesian product) is as below, which is what your query can be simplified to.
"Find a node n with the :Consumer label, and value x for the index mobileNumber, which is connected via a -[:HAS_CONTACT]-> relationshop to a node m with the :Consumer label, and value y for its proprerty mobileNumber. Return both nodes and the relationship, else return nothing."
So, rather than perform two index searches, a cartesian product and a set of expand into operations, neo performs only one index search, an expand all, and a filter.
You can see the result of this simplification by the query planner through the presence of AUTOSTRING parameters in your query profile.
How to Change Query to Implement Search as Desired
If you want to change the query so that it must use an expand into relationship, make the requirement for the relationship optional, or use explicitly iterative execution. Both these queries below will produce the initially expected query profiles.
Optional example:
PROFILE
MATCH (n:Consumer{mobileNumber: "xxx"})
MATCH (m:Consumer{mobileNumber: "yyy"})
WITH n,m
OPTIONAL MATCH (n)-[r:HAS_CONTACT]->(m)
RETURN n,m,r;
Iterative example:
PROFILE
MATCH (n1:Consumer{mobileNumber: "xxx"})
MATCH (m:Consumer{mobileNumber: "yyy"})
UNWIND COLLECT(n1) AS n
MATCH (n)-[r:HAS_CONTACT]->(m)
RETURN n,m,r;
I had a query of this kind, which would basically find a specific node "Statement", find all the nodes connected to it with an :OF relation, find all their connections to one another, as well all the relations of the node "Statement" to other nodes and the node "Statement" itself:
MATCH (s:Statement{uid:"e63cf470-ade4-11e3-bc66-2d7f9b2c7878"}),
c1-[:OF]->s<-[:OF]-c2, c1-[to:TO]->c2
WITH DISTINCT to, c1, c2, s
MATCH c1-[by:BY]->u, c2-[at:AT]->ctx
WHERE to.statement="e63cf470-ade4-11e3-bc66-2d7f9b2c7878"
AND by.statement="e63cf470-ade4-11e3-bc66-2d7f9b2c7878"
AND at.statement="e63cf470-ade4-11e3-bc66-2d7f9b2c7878"
DELETE s,rel,to,by,at;
This worked OK for when there was 3 nodes connected to the node "Statement", but when there's a 100, it crashes the database.
I tried playing around passing different nodes and relationships with a WITH, but it didn't help.
The closest to a solution that I could get was to set up automatic indexing on relationship properties and then execute the deletion with two queries:
MATCH (s:Statement{uid:"e63cf470-ade4-11e3-bc66-2d7f9b2c7878"}),
s-[by:BY]->u, s-[in:IN]->ctx, c-[of:OF]->s DELETE by,in,of,s;
START rel=relationship:relationship_auto_index
(statement="e63cf470-ade4-11e3-bc66-2d7f9b2c7878")
DELETE rel;
2 Questions:
1) I know that the first query took too long because there were too many iterations. How to avoid that?
2) Do you know how to combine the two faster queries above into one so that it works fast and preferably without using the relationship index and START clause?
Thank you!
For this statement
You must not separate the condition on to from the match. Then Cypher will find all matches first and only filter after it is done with that.
MATCH (s:Statement{uid:"e63cf470-ade4-11e3-bc66-2d7f9b2c7878"}),
c1-[:OF]->s<-[:OF]-c2, c1-[to:TO]->c2
WHERE to.statement="e63cf470-ade4-11e3-bc66-2d7f9b2c7878"
WITH DISTINCT to, c1, c2, s
MATCH c1-[by:BY]->u, c2-[at:AT]->ctx
WHERE by.statement="e63cf470-ade4-11e3-bc66-2d7f9b2c7878"
AND at.statement="e63cf470-ade4-11e3-bc66-2d7f9b2c7878"
DELETE s,rel,to,by,at;
Also I'm not sure if this c1-[:OF]->s<-[:OF]-c2, c1-[to:TO]->c2 doesn't span up a cross-product.
Just do this:
MATCH (s:Statement{uid:"e63cf470-ade4-11e3-bc66-2d7f9b2c7878"}),
c1-[:OF]->s<-[:OF]-c2, c1-[to:TO]->c2
WHERE to.statement="e63cf470-ade4-11e3-bc66-2d7f9b2c7878"
RETURN count(*),count(distinct c1), count(distinct c2), count(distinct to)
to see some numbers.
You also don't seem to use (u) and (ctx) in the result? So might be an option to convert that into a condition. (Have to try), then you might even be able to leave of the with (if the cardinality with distinct is not much smaller than without.
....
WHERE c2-[:AT {at.statement:"e63cf470-ade4-11e3-bc66-2d7f9b2c7878"}]->()
AND c1-[:BY {statement:"e63cf470-ade4-11e3-bc66-2d7f9b2c7878"}]->()
DELETE s,rel,to,b
HTH
Would love to get the dataset to try it out.
I have a scenario where I have more than 2 random nodes.
I need to get all possible paths connecting all three nodes. I do not know the direction of relation and the relationship type.
Example : I have in the graph database with three nodes person->Purchase->Product.
I need to get the path connecting these three nodes. But I do not know the order in which I need to query, for example if I give the query as person-Product-Purchase, it will return no rows as the order is incorrect.
So in this case how should I frame the query?
In a nutshell I need to find the path between more than two nodes where the match clause may be mentioned in what ever order the user knows.
You could list all of the nodes in multiple bound identifiers in the start, and then your match would find the ones that match, in any order. And you could do this for N items, if needed. For example, here is a query for 3 items:
start a=node:node_auto_index('name:(person product purchase)'),
b=node:node_auto_index('name:(person product purchase)'),
c=node:node_auto_index('name:(person product purchase)')
match p=a-->b-->c
return p;
http://console.neo4j.org/r/tbwu2d
I actually just made a blog post about how start works, which might help:
http://wes.skeweredrook.com/cypher-it-all-starts-with-the-start/
Wouldn't be acceptable to make several queries ? In your case you'd automatically generate 6 queries with all the possible combinations (factorial on the number of variables)
A possible solution would be to first get three sets of nodes (s,m,e). These sets may be the same as in the question (or contain partially or completely different nodes). The sets are important, because starting, middle and end node are not fixed.
Here is the code for the Matrix example with added nodes.
match (s) where s.name in ["Oracle", "Neo", "Cypher"]
match (m) where m.name in ["Oracle", "Neo", "Cypher"] and s <> m
match (e) where e.name in ["Oracle", "Neo", "Cypher"] and s <> e and m <> e
match rel=(s)-[r1*1..]-(m)-[r2*1..]-(e)
return s, r1, m, r2, e, rel;
The additional where clause makes sure the same node is not used twice in one result row.
The relations are matched with one or more edges (*1..) or hops between the nodes s and m or m and e respectively and disregarding the directions.
Note that cypher 3 syntax is used here.