Background:
I am trying to run a search through a graph and change the search behavior based on if the discovered node belongs to a pre-defined set available before the query is executed.
I can't find any documentation on how to cross-check if a vertex or attribute is present in a set in gremlin.
Examples:
Given: g.V('id1', 'id2', 'id3').as('a')
Find: if a includes 'id4'
OR
Given: g.V('id1', 'id2', 'id3').fold().store('a') => ['id1', 'id2', 'id3']
Find: if a contains id4
One way to approach this is to use the coalesce step. Here is a simple example from the Gremlin Console.
gremlin> g.V(1,2,3).fold().as('found').V(3).coalesce(where(within('found')).constant('found'),constant('not found'))
==>found
gremlin> g.V(1,2,3).fold().as('found').V(4).coalesce(where(within('found')).constant('found'),constant('not found'))
==>not found
Related
I'm using gremlin traversals via a Jupiter Notebook on Amazon Neptune.
I'm trying to filter edges from a specific vertex by their label, but it doesn't seem to work.
some sample data:
%%gremlin
g.addV().property(id, 'u0').as('u0').
addV().property(id, 'u1').as('u1').
addV().property(id, 'u2').as('u2').
addV().property(id, 'u3').as('u3').
addE('freind').
from('u0').
to('u1').
addE('buddy').
from('u0').
to('u2').
addE('foe').
from('u0').
to('u3').
iterate()
and my query:
(It is more complex than needed for this example, but my actual query repeats several times, therefore I can't simply use has('friend').has('buddy') because the next step has other labels.)
%%gremlin
g.withSack(1.0f).V('u0')
.repeat(
bothE().hasNot('foe')
.bothV())
.times(1)
.path().by().by(label)
output:
path[v[u0], freind, v[u1]]
path[v[u0], buddy, v[u2]]
path[v[u0], foe, v[u3]]
I have a user I start with (u0) and want all user who are his friends, buddies, and so on, but not his foes.
unfortunately its not filtering as its supposed to...
any Idea what I'm doing wrong?
The hasNot() step will only filter out elements that have a property with the specified name, in this case a property named foe. Instead, you should look at using not() with hasLabel() to find items that do not have a specific label, as shown here:
g.withSack(1.0f).V('u0')
.repeat(
bothE().not(hasLabel('foe'))
.bothV())
.times(1)
.path().by().by(label)
I am new to gremlin.
I am facing issue in fetching the vertex and edges when sometimes edge from a vertex does not exists.
for example bellow query works fine if it gets all the vertex and edges.
but for one use case edge
`.outE("PRODUCES").`as`("produces"))`
does not exists in db.
in that case bellow query doesnt return any result.
I need your help to resolve this issue.
when edges does not exit then i want input_entity and processed_by in result.
janusGraph.traversal().V()
.has("isActive", "true")
.hasLabel("ENTITY").`as`("input_entity")
.outE("PROCESSED_BY").`as`("processed_by")
.inV().`as`("job")
.outE("PRODUCES").`as`("produces")
.select<String>("job").outE("HAS_STATE")
.`as`("job_state_edge").inV().hasLabel("JOB_STATE").`as`("job_state")
.select<String>("input_entity").outE("HAS_STATE")
.`as`("input_entity_state_edge").inV().hasLabel("ENTITY_STATE").`as`("input_entity_state")
.select<String>("input_entity").outE("CONNECTS_TO").`as`("connects_to")
.inV().hasLabel("ENTITY").has("entityName", TextP.startingWith(rootNamespace))
.`as`("output_entity").outE("HAS_STATE")
.`as`("output_entity_state_edge").inV().hasLabel("ENTITY_STATE").`as`("output_entity_state")
.select<String>("input_entity","output_entity","processed_by","produces","job","job_state","input_entity_state","output_entity_state","input_entity_state_edge","output_entity_state_edge","job_state_edge","connects_to")
.by(elementMap<Element, Any>()).toList()
with optional
janusGraph.traversal().V()
.has("isActive", "true")
.hasLabel("ENTITY").`as`("input_entity")
.outE("HAS_STATE").`as`("input_entity_state_edge").inV().hasLabel("ENTITY_STATE").`as`("input_entity_state")
.select<String>("input_entity").outE("PROCESSED_BY").`as`("processed_by")
.inV().`as`("job").outE("HAS_STATE").`as`("job_state_edge").inV().hasLabel("JOB_STATE").`as`("job_state")
.select<String>("job")
.optional(
outE("PRODUCES").`as`("produces")
.select<String>("input_entity").outE("CONNECTS_TO").`as`("connects_to")
.inV().hasLabel("ENTITY").has("entityName", TextP.startingWith(rootNamespace))
.`as`("output_entity").outE("HAS_STATE").`as`("output_entity_state_edge").inV().hasLabel("ENTITY_STATE").`as`("output_entity_state"))
.select<String>("input_entity","output_entity","processed_by","produces","job","job_state","input_entity_state","output_entity_state","input_entity_state_edge","output_entity_state_edge","job_state_edge","connects_to")
.by(elementMap<Element, Any>()).toList()
There are two Gremlin steps that can help in cases like this. When you have a part of a query that may or may not exist, but you either want the results up to that point if it does not exist or the results afterwards if it does exist, you can wrap that part of the query in an optional step.
For example :
g.V('3').optional(out())
Will either return V['3'] or the adjacent vertices if out yields results.
In cases where you want to select a value that may not exist, you can do something like this:
coalesce(select('a'),constant('No results'))
EDITED to add:
If you need to return multiple results, rather than just using select try a project('a','b,',c') type of approach where each by modulator for the project can contain its own coalesce step.
I have a JanusGraph database with a graph structure as follows:
(Paper)<-[AuthorOf]-(Author)
I'm want to use Gremlin's match clause to query the data and assign the results to a subgraph. This is what I have so far:
g.V().match(
__.as('a').has('Paper','paperTitle', 'The name of my paper'),
__.as('a').in('AuthorOf').outV().as('b')).
select('b').values()
This query returns what I want, the Authors of the paper I'm for which I'm searching. However, I want to assign the results to a subgraph so I can export it using:
sg.io(IoCore.graphml()).writeGraph("/home/ubuntu/myresults.graphml")
Previously, I've achieved this with a different query structure like this:
sg = g.V().has('paperTitle', 'The name of my paper').
inE('AuthorOf').subgraph('sg1').
outV().
cap('sg1').
next()
Is there away to achieve the same results using the 'match()' statement?
After a little trial and error I was able to create a working solution:
sg = g.V().match(
__.as('a').has('Paper','paperTitle', 'ladle pouring guide'),
__.as('a').inE('AuthorOf').subgraph('sg').outV().as('b')).
cap('sg').next()
At first, I was trying to use the 'select' statement to isolate the subgraph. After reviewing the documentation on 'subgraph' and learning more about side-effects in gremlin I realized it wasn't necessary.
The problem is described as following:
I want to find some interested paths and get corresponding properties of vertices or edges, the groovy I used is as following:
g.V().has("p_v_name", "d8e5d39d63c580acdb3eb188a1f4a942").
repeat(__.bothE().otherV().simplePath()).
times(3).emit().
has('p_v_tag').
path().
by(
__.project("label", "id", "p_v_black_tag").
by(__.label()).
by(__.id()).
by(__.choose(__.has('p_v_tag'),
__.properties('p_v_tag').project('value').by(__.value()).fold(),
__.constant([])
)
)
).unfold()
The above code gives me following result:
==>[label:v_user_key,id:749577404608,p_v_tag:[[value:PR016],[value:PR033],[value:PR068]]]
==>[label:e_application_id,id:4jjrk79js-9kcn170g-8ph-nvxhl4s0,p_v_tag:[]]
==>[label:v_application_id,id:1871880949872,p_v_tag:[]]
The result is unfolded for easing reading. It's just a path consisted of two nodes and one edge. The source node has a property p_v_tag, it's of multi-properties. The problem is the target node also has the property p_v_tag, but the code does not output the values.
I checked the target node has the property p_v_tag and it's not empty as following:
gremlin> g.V(1871880949872).properties('p_v_tag')
==>vp[p_v_tag->outdated]
I read the document(http://tinkerpop.apache.org/docs/current/reference) over and over but I can't figure out how to make it right, can any body help me or give me some advice?
I'm not sure why that wouldn't work. What happens if you try this workaround to replace:
by(__.choose(__.has('p_v_tag'),
__.properties('p_v_tag').project('value').by(__.value()).fold(),
__.constant([])
)
with:
by(coalesce(properties('p_v_tag').
project('value').
by(__.value()).
fold(),
constant([]))
Just getting started with gremlin.
Printing out all the Vertex values worked out fine
gremlin> g.V().values()
==>testing 2
==>Cash Processing
==>Sales
==>Marketing
==>Accounting
I was able to find all the directly connected path between my Vertices.
gremlin> g.V().hasLabel('Process')
.repeat(both().simplePath())
.until(hasLabel('Process'))
.dedup().path()
==>[v[25],v[28]]
==>[v[25],v[26]]
==>[v[26],v[27]]
==>[v[26],v[25]]
Now am trying to print out the values in the path like ['Sales', 'Accounting'] instead of [v[25],v[28]]
Not been able to figure out a way yet
Already tried and failed with
Unfold: Does not get me 1-1 mapping
gremlin> g.V().hasLabel('Process').repeat(both().simplePath()).until(hasLabel('Process')).dedup().path().unfold().values()
==>Cash Processing
==>Accounting
==>Cash Processing
==>Sales
==>Sales
==>Marketing
==>Sales
==>Cash Processing
Path seems to be of a different data-type and does not support .values() function
gremlin> g.V().hasLabel('Process')
.repeat(both().simplePath())
.until(hasLabel('Process'))
.dedup().path().values()
org.apache.tinkerpop.gremlin.process.traversal.step.util.ImmutablePath cannot be cast to org.apache.tinkerpop.gremlin.structure.Element
Tried the following google searches and didnt get the answer
gremlin print a path
gremlin get values in a path
and few more word twisting
Found one at here that was for java but that didnt work for me
l = []; g.V().....path().fill(l)
(but cant create list, Cannot set readonly property: list for class: org.apache.tinkerpop.gremlin.structure.VertexProperty$Cardinality
)
I have running it on Gremlin console (running ./gremlin.sh)
You can use the by step to modulate the elements inside the path. For example by supplying valueMap(true) to by you get the properties of the vertices, together with the vertex labels and their ids:
gremlin> g.V().repeat(both().simplePath()).times(1).dedup().path().by(valueMap(true))
==>[[id:1,name:[marko],label:person,age:[29]],[id:3,name:[lop],lang:[java],label:software]]
==>[[id:1,name:[marko],label:person,age:[29]],[id:2,name:[vadas],label:person,age:[27]]]
==>[[id:1,name:[marko],label:person,age:[29]],[id:4,name:[josh],label:person,age:[32]]]
==>[[id:2,name:[vadas],label:person,age:[27]],[id:1,name:[marko],label:person,age:[29]]]
==>[[id:3,name:[lop],lang:[java],label:software],[id:6,name:[peter],label:person,age:[35]]]
==>[[id:4,name:[josh],label:person,age:[32]],[id:5,name:[ripple],lang:[java],label:software]]
I used the modern graph which is one of TinkerPop's toy graphs that are often used for such examples. Your output will look a bit different and you may want to use something else than valueMap(true) for the by modulator. The TinkerPop documentation of the path step itself contains two more advanced examples for path().by() that you might want to check out.