Is it possible via a SLING query to access to a whole node by GUID?
I know that it is possible to do a search by GUID but it means that after doing the search we must do an other query to get the node.
I would like to get a node with only one query.
You can access the node by identifier programatically using this the java.jcr.Session.getNodeByIdentifier
http://www.day.com/maven/javax.jcr/javadocs/jcr-2.0/javax/jcr/Session.html#getNodeByIdentifier(java.lang.String)
If you want to be able to have access to it through a HTTP request, then create a servlet that would expose this functionality.
You can get the node by UUID using either an XPATH query such as
/jcr:root//*[#jcr:uuid='b1e1d3c3-983c-33d6-811c-18d2a8824e03']
or
node = Session.getNodeByIdentifier(String id);
there's a good code sample here:
Jackrabbit Running Queries against UUID
You can also try
propertyIterator = node.getReferences();
This appears to rely on mix:referenceable, which may not be the case for your nodes.
Javadoc: http://www.day.com/maven/javax.jcr/javadocs/jcr-2.0/javax/jcr/Node.html#getReferences()
Related question: Jackrabbit - node.getReferences() not returning anything
Related
I am using AWS Neptune and I have to modify a certain property of a set of EDGEs with specific values. I also need this done in a single transaction. In AWS Neptune, manual transaction logic using tx.commit() and tx.rollback() is not supported. Which means I have to do this operation in a single traversal.
If I was to modify properties of vertices instead of edges, I could have got it done with a query similar to the following one:
g.V(<id 1>).property('name', 'Marko').V(<id 2>).property('name', 'Stephen');
This is because it is possible to select vertices by id in mid traversal, i.e. the GraphTraversal class has V(String ... vertexIds) as a member function.
But this is not the same for the case of edges. I am not able to select edges this way because E(String ... edgeIds) is not a member function of the GraphTraversal class.
Can somebody suggest the correct way I can solve this problem?
Thank you.
Amazon Neptune engine 1.0.1.0.200463.0 added Support for Gremlin Sessions to enable executing multiple Gremlin traversals in a single transaction.
However, you can do it also with a single query like this:
g.E('id1', 'id2', 'id3').coalesce(
has(id, 'id1').property('name','marko'),
has(id, 'id2').property('name','stephan'),
has(id, 'id3').property('name','vadas'))
You can get the same result as a mid traversal E() using V().outE().hasId(<list of IDs>)
I am trying to use AQL to update the whole node collection , named Nodes, depend on the type of edges they have
.
Requirement:
Basically, if 2 entity in Nodes has relation type= "Same", they would be updated with unique groupid properties (same for more than 2)
This would only run one time in the beginning (to populate groupid)
My concept approach:
Use AQL
For each entity inside Node, query out all connectable nodes with type=SAME
Generate an groupid and Update all of them
Write to an lookup object those id
For next entity, do a lookup, skip the entity if their id is there.
What I tried
FOR v,e,p
In 1..10
ANY v
EntityRelationTest
OPTIONS {uniqueVertices:"global",bfs:true}
FILTER p.edges[*].relationType[0]== "EQUALS"
UPDATE v WITH { typeName2:"test1"} IN EntityTest
return NEW
But I am quite new to arangodb AQL, is something like above possible?
In the end, what I use is a customize traversal object running directly inside Foxx in order to get the best of both world: performance and correctness. It seemed that we cannot do the above with only AQL
I'm a newbie to Django as well as neo4j. I'm using Django 1.4.5, neo4j 1.9.2 and neo4django 0.1.8
I've created NodeModel for a person node and indexed it on 'owner' and 'name' properties. Here is my models.py:
from neo4django.db import models as models2
class person_conns(models2.NodeModel):
owner = models2.StringProperty(max_length=30,indexed=True)
name = models2.StringProperty(max_length=30,indexed=True)
gender = models2.StringProperty(max_length=1)
parent = models2.Relationship('self',rel_type='parent_of',related_name='parents')
child = models2.Relationship('self',rel_type='child_of',related_name='children')
def __unicode__(self):
return self.name
Before I connected to Neo4j server, I set auto indexing to True and and gave indexable keys in conf/neo4j.properties file as follows:
# Autoindexing
# Enable auto-indexing for nodes, default is false
node_auto_indexing=true
# The node property keys to be auto-indexed, if enabled
node_keys_indexable=owner,name
# Enable auto-indexing for relationships, default is false
relationship_auto_indexing=true
# The relationship property keys to be auto-indexed, if enabled
relationship_keys_indexable=child_of,parent_of
I followed Neo4j: Step by Step to create an automatic index to update above file and manually create node_auto_index on neo4j server.
Below are the indexes created on neo4j server after executing syndb of django on neo4j database and manually creating auto indexes:
graph-person_conns lucene
{"to_lower_case":"true", "_blueprints:type":"MANUAL","type":"fulltext"}
node_auto_index lucene
{"_blueprints:type":"MANUAL", "type":"exact"}
As suggested in https://github.com/scholrly/neo4django/issues/123 I used connection.cypher(queries) to query the neo4j database
For Example:
listpar = connection.cypher("START no=node(*) RETURN no.owner?, no.name?",raw=True)
Above returns the owner and name of all nodes correctly. But when I try to query on indexed properties instead of 'number' or '*', as in case of:
listpar = connection.cypher("START no=node:node_auto_index(name='s2') RETURN no.owner?, no.name?",raw=True)
Above gives 0 rows.
listpar = connection.cypher("START no=node:graph-person_conns(name='s2') RETURN no.owner?, no.name?",raw=True)
Above gives
Exception Value:
Error [400]: Bad Request. Bad request syntax or unsupported method.
Invalid data sent: (' expected but-' found after graph
I tried other strings like name, person_conns instead of graph-person_conns but each time it gives error that the particular index does not exist. Am I doing a mistake while adding indexes?
My project mainly depends on filtering the nodes based on properties, so this part is really essential. Any pointers or suggestions would be appreciated. Thank you.
This is my first post on stackoverflow. So in case of any missing information or confusing statements please be patient. Thank you.
UPDATE:
Thank you for the help. For the benefit of others I would like to give example of how to use cypher queries to traverse/find shortest path between two nodes.
from neo4django.db import connection
results = connection.cypher("START source=node:`graph-person_conns`(person_name='s2sp1'),dest=node:`graph-person_conns`(person_name='s2c1') MATCH p=ShortestPath(source-[*]->dest) RETURN extract(i in nodes(p) : i.person_name), extract(j in rels(p) : type(j))")
This is to find shortest path between nodes named s2sp1 and s2c1 on the graph. Cypher queries are really cool and help traverse nodes limiting the hops, types of relations etc.
Can someone comment on the performance of this method? Also please suggest if there are any other efficient methods to access Neo4j from Django. Thank You :)
Hm, why are you using Cypher? neo4django QuerySets work just fine for the above if you set the properties to indexed=True (or not, it'll just be slower for those).
people = person_conns.objects.filter(name='n2')
The neo4django docs have some other querying examples, as do the Django docs. Neo4django executes those queries as Cypher on the backend- you really shouldn't need to drop down to writing the Cypher yourself unless you have a very particular traversal pattern or a performance issue.
Anyway, to more directly tackle your question- the last example you used needs backticks to escape the index name, like
listpar = connection.cypher("START no=node:`graph-person_conns`(name='s2') RETURN no.owner?, no.name?",raw=True)
The first example should work. One thought- did you flip the autoindexing on before or after saving the nodes you're searching for? If after, note that you'll have to manually reindex the nodes either using the Java API or by re-setting properties on the node, since it won't have been autoindexed.
HTH, and welcome to StackOverflow!
Root contains one folder, named pending of type sling:folder.
That have numbers of nodes of nt:unstructured type, having name of long value, that long value is very important for my code processing.
Now I want to get top 20 nodes(20 minimum node name , i.e., long value) data from this pending folder.
Can you tell me how can I write the JCR query for this situation ?
Edit No. 1
Repository repository = JcrUtils.getRepository("http://localhost:4502/crx/server");
Session session = repository.login(new SimpleCredentials("admin", "admin".toCharArray()));
// Obtain the query manager for the session via the workspace ...
QueryManager queryManager = session.getWorkspace().getQueryManager();
// Create a query object ...
String expression = "SELECT * FROM [nt:base] AS s WHERE ISDESCENDANTNODE([/pending])";
Query query = queryManager.createQuery(expression, javax.jcr.query.Query.JCR_SQL2);
// Execute the query and get the results ...
QueryResult result = query.execute();
// Iterate over the nodes in the results ...
NodeIterator nodeIter = result.getNodes();
But it gives some order , different than the order present in root node. But that is not in sort form.
Edit No.2
Now I got the functionality of this function. And it working fine now. The thing that I got is order the node just above the destination node, that is mentioned in second parameter of this function.
But the nodes that is coming is of different names(a number). So how can I sort this using orderBefore. Because everytime we are not able to know the right location(destination Relative Path) where we have to put this node.
You probably don't need a query for this, if you have structure such as
/pending/1
/pending/2
...
/pending/999
you can just iterate over the nodes using the JCR Node's getNodes() method, which returns a NodeIterator.
A sling:orderedFolder node type for "pending" gives a predictable ordering of the child nodes.
In general, using the tree structure instead of queries is more efficient in JCR.
Note also that if you're using Jackrabbit having more than about 10'000 child nodes on the same parent can lead to performance issues.
I'm working with Solr indexing data from two sources - real-time "pump" inserting (and updating) documents into Solr and database which holds backups of those documents.
The problem we encountered looks like that - if we make a data import from database while pump is performing inserts, we may index a doc from pump, and later overwrite it with doc extracted from database - which is a backup, so it's probably little outdated.
If we close the pump, import from database and open the pump again, it probably will cause instabilities in our application.
What I'd like to do is tell Solr to not automatically overwrite the document, but do so conditionally (for example by the value of 'last_modified_date' field).
My question is - how can I do it? Do I have to modify Solr source, make a new class overwriting some update processor, or just add some magic lines to solrconfig?
Sorry, but there there is not an option or config to tell Solr to not automatically update documents, but instead use some conditional check. The current model for Solr is that if you insert a document with the same unique id as one already in the index, it will "update" that document by a delete/add operation. Solr also does not currently support the ability to only update specific fields in an existing indexed document. Please see issue SOLR-139 for more details.
Based on the scenario you have described, I would suggest that you create a process outside of Solr that handles the retrieval of items from your data sources and then performs the conditional check to see what is in the index already and determine if an update to the index is necessary.
You can use solr script processors to check if that document exists proceeds in its accordance
Below code only works when solr uses java 8
function processAdd(cmd) {
doc = cmd.solrDoc;
var previousDoc=null;
try {
// create a term type object
var Term = Java.type("org.apache.lucene.index.Term");
var TermObject =new Term("fieldForSearchTryUnique","Value of field");
//retrieve document id from solr return -1 if not present
previousDocId= req.getSearcher().getFirstMatch(TermObject);
if(-1!=perviousDocId) {
// get complete document from solr for that searched field
previousDoc=req.getSearcher().doc(previousDocId);
// do required process here
}
}
catch(err) {
logger.error("error in update processor "+err)
}
}