Question

序曲：几个月使用Gremlin“方言”为FaunusGraph＆amp; TitanGraph，非常了解功能和句法差异。已成功使用Faunus脚本步骤（http://architects.dzone.com/articles/distributed-graph-computing，https://github.com/thinkaurelius/faunus/blob/master/src/main/java/com/thinkaurelius/faunus/mapreduce/sideeffect/ScriptMap.java）进行相对简单的删除操作。子图的变异。

问题：实现了一个复杂的变异脚本映射，以根据命名属性的面向方向的约定将边缘属性“移动”到外顶点或顶点。我的TitanGraph Gremlin原型适用于小图，但我无法使扩展的实现工作：地图成功完成但图形没有改变（我提交了更改）。注意：我的Logger对象只输出显示前缀args的第一条INFO消息，表明我没有满足边缘命名空间保护条件（我没有条件运行，但没有更改）。以下是我的代码（来自内部网络的指法，因此可能存在拼写错误）

//faunus pipe driver - usage gremlin -e faunus.ns.set-props.grm
import java.io.Console

//get args
console=System.console()
arg=console.readLine('> type <namespace>;<faunus.ns.set-props.mapper_path>;<from_prefix>;<to_prefix>
inargs=arg.split(";")

//establish FaunusGraph connection
f=FaunusFactory.open('titan-client.properties')
f.getConf().set("faunus.graph.input.titan.storage.read-consistency-level", "ALL")
f.getConf().set("faunus.graph.input.titan.storage.write-consistency-level", "ALL")

//Faunus pipe incl. script step
f.V().has("_namespace", inargs[0]).script(inargs[1], inargs[2], inargs[3]

//script map - usage f.V().has("_namespace", <namespace_string>).script(<this_script_path>, <outV_key_prefix_string>, <inV_key_prefix_string>)

def g
def mylog

def setup(args) {
    mylog=java.util.logging.Logger.getLogger("script_map")
    println("configuring graph ...")
    conf=new BaseConfiguration()
    conf.setProperty("storage.backend", "cassandra")
    conf.setProperty("storage.keyspace", "titan")
    conf.setProperty("storage.index.index-name", "titan")
    conf.setProperty("storage.hostname", "localhost")
    g=TitanFactory.open(conf)
}

def map(v, args) {
    mylog.info("*****READ***** args: "+args[0].toString()+", "+args[1].toString())

    //fetch all edges incident on Titan vertex corresponding to incoming Faunus vertex
    gv=g.v(v.id)
    edges=gv.bothE();null

    //iterate through incident edges
    while(edges.hasNext()) {
        e=edges.next()
        if (e.hasProperty("_namespace")) { //_namespace removed from previously processed edges
            /*fetch terminal vertices of current edge, add incidence & adjacency props
            to support metrics and analytics
            */
            from=e.getVertex(OUT)
            from.setProperty("inV_degree", from.in().count())
            from.setProperty("inE_degree", from.inE().count())
            from.setProperty("outV_degree" from.out().count())
            from.setProperty("outE_degree", from.outE().count())

            to=e.getVertex(IN)
            to.setProperty("inV_degree", from.in().count())
            to.setProperty("inE_degree", from.inE().count())
            to.setProperty("outV_degree" from.out().count())
            to.setProperty("outE_degree", from.outE().count())

            mylog.info("*****READ*****edge id:  "+e.id)
            mylog.info("*****READ*****edge vertices:  from id"+fromid+"; to id:  "+to.id)

            //fetch property keys of current edge
            ekeys=e.getPropertyKeys()

            //iterate through edge property keys
            for(String ekey:ekeys)
                eprop=e.getProperty(ekey) //get value of current property key
                goodprop=!(eprop == "" || eprop == null)
                mylog.info("*****READ*****edge key/value: "+ekey+"="eprop)

                /*determine placement of current key/value on one or neither of the 
               terminal vertices based on key prefix arges and property value,
               remove prefix from re-assigned key/value
               */

               if(ekey.startsWith(args[0]) && goodprop) {
                   vkey=ekey.split(args[0])[1]
                   if(!from.hasProperty(vkey)) from.setProperty(vkey, eprop)
                   else {
                       vprop=from.getProperty(vkey)
                       if(!vprop.equal(eprop) from.setProperty(vkey, vprop+";"+eprop)
                   }
                   mylog.info("*****READ*****from vertex key/value:  "+vkey+"="+from.getProperty(vkey)
               }
               else if(ekey.startsWith(args[1]) && goodprop) {
                   vkey=ekey.split(args[1])[1]
                   if(!to.hasProperty(vkey)) to.setProperty(vkey, eprop)
                   else {
                       vprop=to.getProperty(vkey)
                       if(!vprop.equal(eprop) to.setProperty(vkey, vprop+";"+eprop)
                   }
                   mylog.info("*****READ*****tovertex key/value:  "+vkey+"="+to.getProperty(vkey)
               }

               //if current edge property key is re-assigned, remove it from the edge
               if(ekey.startsWith(args[0]) || ekey.startsWith(args[1])) {
                   e.removeProperty(ekey)
                   if(e.hasProperty(ekey) println(ekey+" NOT remvoded from edge")
                   else println(ekey+ "removed from edge")
                }
                e.removeProperty("_namespace") // marks edge as processed per outer loop guard
            }
        }
    }
    g.commit()
}

def cleanup(args) {
    g.shutdown()
}

Answer 1

这一行：

if (e.hasProperty("_namespace")) {

hasProperty似乎不在Blueprints API或Titan API中。既然如此，我不确定这个代码在较小的测试数据库中是如何工作的，因为它总是会解析为false，你永远不会看到if语句的内部：

gremlin> x = TinkerGraphFactory.createTinkerGraph()
==>tinkergraph[vertices:6 edges:6]
gremlin> v = x.V('name','marko').next()                     
==>v[1]
gremlin> if (v.hasProperty('name')) { true } else { false } 
==>false

我想你真的想尝试一下：

gremlin> if (v.getProperty('name')) { true } else { false }
==>true
gremlin> if (v.getProperty('xxx')) { true } else { false } 
==>false

faunus脚本地图完成但不变异图

1 个答案: