support get edge data through ngql (#64)

Author: Nicole00

nebula-algorithm/src/main/resources/application.conf

@@ -10,7 +10,7 @@
   }
 
   data: {
-    # data source. optional of nebula,csv,json
+    # data source. optional of nebula,nebula-ngql,csv,json
     source: csv
     # data sink, means the algorithm result will be write into this sink. optional of nebula,csv,text
     sink: csv

nebula-algorithm/src/main/scala/com/vesoft/nebula/algorithm/Main.scala

@@ -119,6 +119,10 @@ object Main {
         val reader = new NebulaReader(spark, configs, partitionNum)
         reader.read()
       }
+      case "nebula-ngql" => {
+        val reader = new NebulaReader(spark, configs, partitionNum)
+        reader.readNgql()
+      }
       case "csv" => {
         val reader = new CsvReader(spark, configs, partitionNum)
         reader.read()

nebula-algorithm/src/main/scala/com/vesoft/nebula/algorithm/config/Configs.scala

@@ -90,8 +90,18 @@ object NebulaConfigEntry {
     } else {
       List()
     }
-    val readConfigEntry =
+    val readConfigEntry = if (nebulaConfig.hasPath("read.ngql")) {
+      val readGraphAddress = nebulaConfig.getString("read.graphAddress")
+      val ngql             = nebulaConfig.getString("read.ngql")
+      NebulaReadConfigEntry(readMetaAddress,
+                            readSpace,
+                            readLabels,
+                            readWeightCols,
+                            readGraphAddress,
+                            ngql)
+    } else {
       NebulaReadConfigEntry(readMetaAddress, readSpace, readLabels, readWeightCols)
+    }
 
     val graphAddress     = nebulaConfig.getString("write.graphAddress")
     val writeMetaAddress = nebulaConfig.getString("write.metaAddress")
@@ -203,11 +213,13 @@ case class NebulaConfigEntry(readConfigEntry: NebulaReadConfigEntry,
 case class NebulaReadConfigEntry(address: String = "",
                                  space: String = "",
                                  labels: List[String] = List(),
-                                 weightCols: List[String] = List()) {
+                                 weightCols: List[String] = List(),
+                                 graphAddress: String = "",
+                                 ngql: String = "") {
   override def toString: String = {
     s"NebulaReadConfigEntry: " +
       s"{address: $address, space: $space, labels: ${labels.mkString(",")}, " +
-      s"weightCols: ${weightCols.mkString(",")}}"
+      s"weightCols: ${weightCols.mkString(",")}, ngql: $ngql}"
   }
 }
 

nebula-algorithm/src/main/scala/com/vesoft/nebula/algorithm/reader/DataReader.scala

@@ -65,6 +65,54 @@ class NebulaReader(spark: SparkSession, configs: Configs, partitionNum: String)
     }
     dataset
   }
+
+  def readNgql(): DataFrame = {
+    val metaAddress  = configs.nebulaConfig.readConfigEntry.address
+    val graphAddress = configs.nebulaConfig.readConfigEntry.graphAddress
+    val space        = configs.nebulaConfig.readConfigEntry.space
+    val labels       = configs.nebulaConfig.readConfigEntry.labels
+    val weights      = configs.nebulaConfig.readConfigEntry.weightCols
+    val partition    = partitionNum.toInt
+    val ngql         = configs.nebulaConfig.readConfigEntry.ngql
+
+    val config =
+      NebulaConnectionConfig
+        .builder()
+        .withMetaAddress(metaAddress)
+        .withGraphAddress(graphAddress)
+        .withConenctionRetry(2)
+        .build()
+
+    var dataset: DataFrame = null
+    for (i <- labels.indices) {
+      val returnCols: ListBuffer[String] = new ListBuffer[String]
+      if (configs.dataSourceSinkEntry.hasWeight && weights.nonEmpty) {
+        returnCols.append(weights(i))
+      }
+      val nebulaReadEdgeConfig: ReadNebulaConfig = ReadNebulaConfig
+        .builder()
+        .withSpace(space)
+        .withLabel(labels(i))
+        .withPartitionNum(partition)
+        .withNgql(ngql)
+        .build()
+      if (dataset == null) {
+        dataset = spark.read.nebula(config, nebulaReadEdgeConfig).loadEdgesToDF()
+        if (weights.nonEmpty) {
+          dataset = dataset.select("_srcId", "_dstId", weights(i))
+        }
+      } else {
+        var df = spark.read
+          .nebula(config, nebulaReadEdgeConfig)
+          .loadEdgesToDF()
+        if (weights.nonEmpty) {
+          df = df.select("_srcId", "_dstId", weights(i))
+        }
+        dataset = dataset.union(df)
+      }
+    }
+    dataset
+  }
 }
 
 class CsvReader(spark: SparkSession, configs: Configs, partitionNum: String)