CODEWITHSUNDEEP
neo4jcyphergraph-databases
Lundin
Lundin

Reputation: 311

Adding labels to neo4j graph 2.0M01 with Cypher

Trying out the latest Neo4j 2.0 M01. I also Downloaded the full cinecast graph.db and configured it to work with 2.0 store according to the great video tutorial by Michael, see here: http://vimeo.com/63707662

I would like to get familiar with labels so my idea was to add some labels to some nodes being index as User,Person.

start n=node:Person("id:") set n:Humans return count ();

That worked, it added labels to all nodes being indexed (but i cant see it visually in the web console..but anyway it is there when query for it)

However this doesn't work:

neo4j-sh (0)$ start n=node:Person("id:*")  match n where ID(n)>700 and ID(n)<710 set n:Journalist return n;

ResourceAcquisitionFailedException: The transaction is marked for rollback only

Two problems: is there today any typecast function string to int? The ID(n) was the only thing i could come up with to update partial nodes of the index since id,names etc are strings.

And secondly why doesnt it set a Journalist label onto the node group above? http://docs.neo4j.org/chunked/2.0.0-M01/query-set.html#set-set-a-label-on-a-node

Als,Can Labels be multiple word like:

start a=node(1,2,3,4) 
match a 
where a.name='Anders' 
set a:helicopter pilot
return a

Error: expected valid query body "set a:helicopter pilot "

And finally, in the Neo4j api docs when trying out the queries there is something with the node(0) root that doesn't work, following is a valid query right (at least useful)?

start a=node(*) 
match a 
where a.name='Anders' 
return a

Error: org.neo4j.cypher.EntityNotFoundException: The property 'name' does not exist on Node[0]

Thank you!

Upvotes: 2

Views: 2717

Answers (1)

Michael Hunger
Michael Hunger

Reputation: 41676

Great that you try it out. Your feedback is very appreciated.

START n=node:Person("id:*")
MATCH n where ID(n)>700 and ID(n)<710 
SET n:Journalist 
RETURN n; //or count(*)

ResourceAcquisitionFailedException: The transaction is marked for rollback only

That error shouldn't happen.

btw. in that query you don't need MATCH.

you can update partial sets of nodes with WITH and LIMIT / SKIP

START n=node:Person("id:*") 
WITH n
// optional ORDER BY n.name
SKIP 700 LIMIT 10
SET n:Journalist
RETURN n;

Currently there is only implicit typecasting afaik, e.g. when adding strings and numbers.

The Journalist label wasn't set b/c of the failed transaction.

Labels can be multiple words, if you quote them with backticks.

start a=node(1,2,3,4) 
where a.name='Anders' 
set a:`helicopter pilot`
return a

Again you don't need MATCH in this query.

If there is a node which doesn't have a name property you have to check if it is there before, e.g. with

has(a.name) and a.name='Anders'

there are two shortcuts, one that returns true if the property is not there (property optional)

a.name? ='Anders'

and one that returns false when the props is not there (property required)

a.name! ='Anders'

start a=node(*) 
match a 
where a.name?='Anders' 
return a

Upvotes: 4

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