Hosted By Map - added new aggregator to get just one result per datasource id

dhp-workflows/dhp-graph-mapper/src/main/java/eu/dnetlib/dhp/oa/graph/hostedbymap/Aggregators.scala

@@ -103,4 +103,40 @@ object Aggregators {
     transformedData
   }
 
+  def datasourceToSingleIdAggregator: TypedColumn[EntityInfo, EntityInfo] = new Aggregator[EntityInfo, EntityInfo, EntityInfo]{
+    override def zero: EntityInfo = EntityInfo.newInstance("","","")
+
+    override def reduce(b: EntityInfo, a:EntityInfo):  EntityInfo = {
+      return merge(b, a)
+    }
+    override def merge(b1: EntityInfo, b2: EntityInfo): EntityInfo = {
+      if (b1 == null){
+        return b2
+      }
+      if(b2 == null){
+        return b1
+      }
+      if(!b1.getHb_id.equals("")){
+        return b1
+      }
+      b2
+
+    }
+    override def finish(reduction: EntityInfo):  EntityInfo = reduction
+    override def bufferEncoder: Encoder[EntityInfo] = Encoders.bean(classOf[EntityInfo])
+
+    override def outputEncoder: Encoder[EntityInfo] = Encoders.bean(classOf[EntityInfo])
+  }.toColumn
+
+
+  def datasourceToSingleId(df:Dataset[EntityInfo]): Dataset[EntityInfo] = {
+    val transformedData : Dataset[EntityInfo] = df
+      .groupByKey(_.getHb_id)(Encoders.STRING)
+      .agg(Aggregators.datasourceToSingleIdAggregator)
+      .map{
+        case (id:String , res: EntityInfo) => res
+      }(Encoders.bean(classOf[EntityInfo]))
+
+    transformedData
+  }
 }