Max() function equivalent in gremlin

[Laksh Krishna]

Is there a equivalent of max() function in gremlin ? I am having to run gremlin queries that need to return an edge that has the max value (say an long value) which I then have to evaluate using filters.

[Marko Rodriguez]

Hi,

You can do this:

gremlin> g.v(1).transform{x = it.outE.weight.max(); it.outE.find{it.weight == x}}

==>e[8][1-knows->4]

Its not the prettiest, but does the trick. You might want to wrap that into a function and make it more efficient as well (no need to iterate over the edge list twice).

def maxEdge(v) {

x = v.outE.weight.max()

v.outE.find{it.weight == x}

}

gremlin> g.v(1).transform{maxEdge(it)}

==>e[8][1-knows->4]

HTH,

Marko.

http://markorodriguez.com

On May 8, 2013, at 3:13 PM, Laksh Krishna <lkri...@gmail.com> wrote:

Is there a equivalent of max() function in gremlin ? I am having to run gremlin queries that need to return an edge that has the max value (say an long value) which I then have to evaluate using filters.

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[Laksh Krishna]

Marko,

Thanks. That works. 

How do I do this in a loop? Instead on running this on a specific vertex I want to get all vertices that have maximum weights (given each of them may have different weight recordings).

Thanks,

Laksh

[Laksh Krishna]

I tried this inside Rexster Doghouse and the function always returns a null in the gremlin shell. When i proceeded with the actual call to the function I got a MissingMethodException. 

>javax.script.ScriptException: groovy.lang.MissingMethodException: No signature of method: com.tinkerpop.gremlin.groovy.GremlinGroovyPipeline.tranform() is applicable for argument types: (Script587$_run_closure1) values: [Script587$_run_closure1@ed80ed8]
Possible solutions: transform(com.tinkerpop.pipes.PipeFunction), transform(groovy.lang.Closure), random(java.lang.Double)

Noticed that in one of the thread someone reported the same problem with function defs. Wanted to know if this is a groovyengine issue or has it been fixed in the latest gremlin version.

On Wednesday, May 8, 2013 4:51:31 PM UTC-5, Marko A. Rodriguez wrote:

[Marko Rodriguez]

javax.script.ScriptException: groovy.lang.MissingMethodException: No signature of method: com.tinkerpop.gremlin.groovy.GremlinGroovyPipeline.tranform() is applicable for argument types: (Script587$_run_closure1) values: [Script587$_run_closure1@ed80ed8]

You misspelled the method.

You have 'tranform'

Its 'transform' (note the 's').

Marko.

http://markorodriguez.com

[Laksh Krishna]

Marko,

Thanks. My bad. I fixed the typo and it looks like the function is being called.

However, I run into this problem with variable 'it' being null inside the find() function. I tried having all in one call (like you had provided in the first example) as well as embedded within the function. Either case resulted in 'it' being null.

gremlin>> Cannot get property 'therapy|date' on null object

This is what's being defined in gremlin using the Doghouse tool:

def maxEdge(v)
{ x = v.outE('patient|hastherapy').property('therapy|date').max;
 return v.outE('patient|hastherapy').find{it.getProperty('therapy|date') == x}
}

g.V('case|id',XXXXXX).outE('case|haspatient').inV.transform{maxEdge(it)}

I tried using this within a JUnit test case using Gremlin APIs and got a similar result. Not sure if find() function is loosing handle on the iterator.

Thanks,
Laksh

[Laksh Krishna]

Turned out that I had something going on in Rexster. Tried restarting Rexster and submitted the same query and it works now within DogHouse as well as in my unit test.