I'm using the Neography gem to interact with a Neo4j database through the REST API. I don't see any way in Neography itself (though if it's there, I'd love to use it!), nor have I been able to find by searching on Google whether this is possible directly through the REST API itself. Does anyone out there with Neo4j experience happen to know?
With Neography, you can send this Gremlin script:
#neo = Neography::Rest.new
#neo.execute_script("g.clear()")
to remove all the nodes and relationships.
To clear all nodes and relationships except the root node, use the solution provided in neography wiki
#neo = Neography::Rest.new
#neo.execute_query("START n0=node(0),nx=node(*) MATCH n0-[r0?]-(),nx-[rx?]-() WHERE nx <> n0 DELETE r0,rx,nx")
Related
Is it possible to create an index on the nodes/relationships of a graph in AGE? If so, what is the syntax?
I was unable to find anything about it in the documentation.
There is an issue currently open related to this:
https://github.com/apache/age/issues/45
At this moment seems there no complete support for this. There is an Open PR for OpenCypher as well:
https://github.com/opencypher/openCypher/pull/166
If however you are okay with Neo4j you can look into it.
For more information regarding implementation in Cypher queries: https://github.com/Mats-SX/openCypher/blob/c542f94f07fb934254748f4f2ce44612d45866a3/cip/vendor-extensions/neo4j/CIP2016-12-14-Neo4j-indexes.adoc
There is a Java and CLI-interface to query Yarn RM for node-to-nodelabel (and inverse) mappings. Is there a way to do this via the REST-API as well?
An initial RM-API search revealed only node-label based job submissions as an option.
Sadly that is actually broken in MapR-Hadoop (6.1 as of 6/6/19), so my code has to work around that, by implementing the correct scheduling itself. This works (barely - more broken APIs here as well) using the YarnClient Java API.
But as I want to schedule jobs against different resource managers at the same time, behind firewalls, the REST-API is the most compelling option to achieve this, and the YarnClient API's RPC backend can't be easily transported.
My current worst-case solution would be to parse the YARN-WebUI in some way.
The only solution I found so far:
Request /ws/v1/cluster/nodes - this gets you all nodes.
FlatMap/Distinct on each node's nodeLabels, if you need just the list of node labels. Filter by nodeLabel, if you need all nodes for a specified label.
This does mean, that you always have to query all nodes, then sort/filter/arrange by NodeLabels, which is a lot of client-side magic. But apparently there's no GetNodesToLabel or even GetClusterNodeLabels to help us out.
I assume getLabelsToNodes is just a client-side implementation, as the protocol doesn't define the API, so that's right out the window for REST, unless implemented in the WebService.
We need to restrict a MarkLogic search to the latest version of managed documents, using Marklogic's REST api. We're using MarkLogic 6.
Using straight xquery, you can use dls:documents-query() as an additional-query option (see
Is there any way to restrict marklogic search on specific version of the document).
But the REST api requires XML, not arbitrary xquery. You can turn ordinary cts queries into XML easily enough (execute <some-element>{cts:word-query("hello world")}</some-element> in QConsole).
If I try that with dls:documents-query() I get this:
<cts:properties-query xmlns:cts="http://marklogic.com/cts">
<cts:registered-query>
<cts:id>17524193535823153377</cts:id>
</cts:registered-query>
</cts:properties-query>
Apart from being less than totally transparent... how safe is that number? We'll need to put it in our query options, so it's not something we can regenerate every time we need it. I've looked on two different installations here and the the number's the same, but is it guaranteed to be the same, and will it ever change? On, for example, a MarkLogic upgrade?
Also, assuming the number is safe, will the registered-query always be there? The documentation says that registered queries may be cleared by the system at various times, but it's talking about user-defined registered queries, and I'm not sure how much of that applies to internal queries.
Is this even the right approach? If we can't do this we can always set up collections and restrict the search that way, but we'd rather use dls:documents-query if possible.
The number is a registered query id, and is deterministic. That is, it will be the same every time the query is registered. That behavior has been invariant across a couple of major releases, but is not guaranteed. And as you already know, the server can unregister a query at any time. If that happens, any query using that id will throw an XDMP-UNREGISTERED error. So it's best to regenerate the query when you need it, perhaps by calling dls:documents-query again. It's safest to do this in the same request as the subsequent search.
So I'd suggest extending the REST API with your own version of the search endpoint. Your new endpoint could add dls:documents-query to the input query. That way the registered query would be generated in the same request with the subsequent search. For ML6, http://docs.marklogic.com/6.0/guide/rest-dev/extensions explains how to do this.
The call to dls:documents-query() makes sure the query is actually registered (on the fly if necessary), but that won't work from REST api. You could extend the REST api with a custom extension as suggested by Mike, but you could also use the following:
cts:properties-query(
cts:and-not-query(
cts:element-value-query(
xs:QName("dls:latest"),
"true",
(),
0
),
cts:element-query(
xs:QName("dls:version-id"),
cts:and-query(())
)
)
)
That is the query that is registered by dls:documents-query(). Might not be future proof though, so check at each upgrade. You can find the definition of the function in /Modules/MarkLogic/dls.xqy
HTH!
This is for people with knowledge on REST and Neo4j.
Is it possible to name a node before creating it in Neo4j ?
Typical Restful thing, you create a URI "XXX/db/data/node/mynode" and you want to create a node with this identifier if it is not existent in the moment.
For all that I have been researching (and testing) to the present moment, the answer is : "no it is not possible, neo4j will just always automatically give ids to the created nodes and the attempt to do create a URI and use POST to cause its creation will result in 405"
Thanks in advance.
That's correct, you can't set the id of a node. What you can do is to add some other kind of id as a property, see create node with properties. Just make sure it's indexed automatically and then you can query that index for exact matches.
How to get Best Practical's RT configuration (list of users, queues, possible values for status field, possible values for custom field) via its REST interface? Or may be there is some web page where this information can be easily parsed from? I found sources for REST interface in rt-3.8.7.tar.gz/rt-3.8.7/share/html/REST/1.0 but I know little of perl and don't understand how these scripts are executed and what they are doing.
Have you tried: http://wiki.bestpractical.com/view/REST