[SPARK-10117] [MLLIB] Implement SQL data source API for reading LIBSVM data

It is convenient to implement data source API for LIBSVM format to have a better integration with DataFrames and ML pipeline API.

Two option is implemented.
* `numFeatures`: Specify the dimension of features vector
* `featuresType`: Specify the type of output vector. `sparse` is default.

Author: lewuathe <lewuathe@me.com>

Closes #8537 from Lewuathe/SPARK-10117 and squashes the following commits:

986999d [lewuathe] Change unit test phrase
11d513f [lewuathe] Fix some reviews
21600a4 [lewuathe] Merge branch 'master' into SPARK-10117
9ce63c7 [lewuathe] Rewrite service loader file
1fdd2df [lewuathe] Merge branch 'SPARK-10117' of github.com:Lewuathe/spark into SPARK-10117
ba3657c [lewuathe] Merge branch 'master' into SPARK-10117
0ea1c1c [lewuathe] LibSVMRelation is registered into META-INF
4f40891 [lewuathe] Improve test suites
5ab62ab [lewuathe] Merge branch 'master' into SPARK-10117
8660d0e [lewuathe] Fix Java unit test
b56a948 [lewuathe] Merge branch 'master' into SPARK-10117
2c12894 [lewuathe] Remove unnecessary tag
7d693c2 [lewuathe] Resolv conflict
62010af [lewuathe] Merge branch 'master' into SPARK-10117
a97ee97 [lewuathe] Fix some points
aef9564 [lewuathe] Fix
70ee4dd [lewuathe] Add Java test
3fd8dce [lewuathe] [SPARK-10117] Implement SQL data source API for reading LIBSVM data
40d3027 [lewuathe] Add Java test
7056d4a [lewuathe] Merge branch 'master' into SPARK-10117
99accaa [lewuathe] [SPARK-10117] Implement SQL data source API for reading LIBSVM data

mllib/src/main/resources/META-INF/services/org.apache.spark.sql.sources.DataSourceRegister

+org.apache.spark.ml.source.libsvm.DefaultSource

mllib/src/main/scala/org/apache/spark/ml/source/libsvm/LibSVMRelation.scala

+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.ml.source.libsvm
+
+import com.google.common.base.Objects
+
+import org.apache.spark.Logging
+import org.apache.spark.annotation.Since
+import org.apache.spark.mllib.linalg.VectorUDT
+import org.apache.spark.mllib.util.MLUtils
+import org.apache.spark.rdd.RDD
+import org.apache.spark.sql.types.{StructType, StructField, DoubleType}
+import org.apache.spark.sql.{Row, SQLContext}
+import org.apache.spark.sql.sources._
+
+/**
+ * LibSVMRelation provides the DataFrame constructed from LibSVM format data.
+ * @param path File path of LibSVM format
+ * @param numFeatures The number of features
+ * @param vectorType The type of vector. It can be 'sparse' or 'dense'
+ * @param sqlContext The Spark SQLContext
+ */
+private[ml] class LibSVMRelation(val path: String, val numFeatures: Int, val vectorType: String)
+    (@transient val sqlContext: SQLContext)
+  extends BaseRelation with TableScan with Logging with Serializable {
+
+  override def schema: StructType = StructType(
+    StructField("label", DoubleType, nullable = false) ::
+      StructField("features", new VectorUDT(), nullable = false) :: Nil
+  )
+
+  override def buildScan(): RDD[Row] = {
+    val sc = sqlContext.sparkContext
+    val baseRdd = MLUtils.loadLibSVMFile(sc, path, numFeatures)
+
+    baseRdd.map { pt =>
+      val features = if (vectorType == "dense") pt.features.toDense else pt.features.toSparse
+      Row(pt.label, features)
+    }
+  }
+
+  override def hashCode(): Int = {
+    Objects.hashCode(path, schema)
+  }
+
+  override def equals(other: Any): Boolean = other match {
+    case that: LibSVMRelation => (this.path == that.path) && this.schema.equals(that.schema)
+    case _ => false
+  }
+
+}
+
+/**
+ * This is used for creating DataFrame from LibSVM format file.
+ * The LibSVM file path must be specified to DefaultSource.
+ */
+@Since("1.6.0")
+class DefaultSource extends RelationProvider with DataSourceRegister {
+
+  @Since("1.6.0")
+  override def shortName(): String = "libsvm"
+
+  private def checkPath(parameters: Map[String, String]): String = {
+    require(parameters.contains("path"), "'path' must be specified")
+    parameters.get("path").get
+  }
+
+  /**
+   * Returns a new base relation with the given parameters.
+   * Note: the parameters' keywords are case insensitive and this insensitivity is enforced
+   * by the Map that is passed to the function.
+   */
+  override def createRelation(sqlContext: SQLContext, parameters: Map[String, String])
+    : BaseRelation = {
+    val path = checkPath(parameters)
+    val numFeatures = parameters.getOrElse("numFeatures", "-1").toInt
+    /**
+     * featuresType can be selected "dense" or "sparse".
+     * This parameter decides the type of returned feature vector.
+     */
+    val vectorType = parameters.getOrElse("vectorType", "sparse")
+    new LibSVMRelation(path, numFeatures, vectorType)(sqlContext)
+  }
+}

mllib/src/test/java/org/apache/spark/ml/source/JavaLibSVMRelationSuite.java

+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.ml.source;
+
+import java.io.File;
+import java.io.IOException;
+
+import com.google.common.base.Charsets;
+import com.google.common.io.Files;
+
+import org.junit.After;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import org.apache.spark.api.java.JavaSparkContext;
+import org.apache.spark.mllib.linalg.DenseVector;
+import org.apache.spark.mllib.linalg.Vectors;
+import org.apache.spark.sql.DataFrame;
+import org.apache.spark.sql.Row;
+import org.apache.spark.sql.SQLContext;
+import org.apache.spark.util.Utils;
+
+
+/**
+ * Test LibSVMRelation in Java.
+ */
+public class JavaLibSVMRelationSuite {
+  private transient JavaSparkContext jsc;
+  private transient SQLContext jsql;
+  private transient DataFrame dataset;
+
+  private File tmpDir;
+  private File path;
+
+  @Before
+  public void setUp() throws IOException {
+    jsc = new JavaSparkContext("local", "JavaLibSVMRelationSuite");
+    jsql = new SQLContext(jsc);
+
+    tmpDir = Utils.createTempDir(System.getProperty("java.io.tmpdir"), "datasource");
+    path = new File(tmpDir.getPath(), "part-00000");
+
+    String s = "1 1:1.0 3:2.0 5:3.0\n0\n0 2:4.0 4:5.0 6:6.0";
+    Files.write(s, path, Charsets.US_ASCII);
+  }
+
+  @After
+  public void tearDown() {
+    jsc.stop();
+    jsc = null;
+    Utils.deleteRecursively(tmpDir);
+  }
+
+  @Test
+  public void verifyLibSVMDF() {
+    dataset = jsql.read().format("libsvm").option("vectorType", "dense").load(path.getPath());
+    Assert.assertEquals("label", dataset.columns()[0]);
+    Assert.assertEquals("features", dataset.columns()[1]);
+    Row r = dataset.first();
+    Assert.assertEquals(1.0, r.getDouble(0), 1e-15);
+    DenseVector v = r.getAs(1);
+    Assert.assertEquals(Vectors.dense(1.0, 0.0, 2.0, 0.0, 3.0, 0.0), v);
+  }
+}

mllib/src/test/scala/org/apache/spark/ml/source/LibSVMRelationSuite.scala

+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.ml.source
+
+import java.io.File
+
+import com.google.common.base.Charsets
+import com.google.common.io.Files
+
+import org.apache.spark.SparkFunSuite
+import org.apache.spark.mllib.linalg.{SparseVector, Vectors, DenseVector}
+import org.apache.spark.mllib.util.MLlibTestSparkContext
+import org.apache.spark.util.Utils
+
+class LibSVMRelationSuite extends SparkFunSuite with MLlibTestSparkContext {
+  var path: String = _
+
+  override def beforeAll(): Unit = {
+    super.beforeAll()
+    val lines =
+      """
+        |1 1:1.0 3:2.0 5:3.0
+        |0
+        |0 2:4.0 4:5.0 6:6.0
+      """.stripMargin
+    val tempDir = Utils.createTempDir()
+    val file = new File(tempDir.getPath, "part-00000")
+    Files.write(lines, file, Charsets.US_ASCII)
+    path = tempDir.toURI.toString
+  }
+
+  test("select as sparse vector") {
+    val df = sqlContext.read.format("libsvm").load(path)
+    assert(df.columns(0) == "label")
+    assert(df.columns(1) == "features")
+    val row1 = df.first()
+    assert(row1.getDouble(0) == 1.0)
+    val v = row1.getAs[SparseVector](1)
+    assert(v == Vectors.sparse(6, Seq((0, 1.0), (2, 2.0), (4, 3.0))))
+  }
+
+  test("select as dense vector") {
+    val df = sqlContext.read.format("libsvm").options(Map("vectorType" -> "dense"))
+      .load(path)
+    assert(df.columns(0) == "label")
+    assert(df.columns(1) == "features")
+    assert(df.count() == 3)
+    val row1 = df.first()
+    assert(row1.getDouble(0) == 1.0)
+    val v = row1.getAs[DenseVector](1)
+    assert(v == Vectors.dense(1.0, 0.0, 2.0, 0.0, 3.0, 0.0))
+  }
+
+  test("select a vector with specifying the longer dimension") {
+    val df = sqlContext.read.option("numFeatures", "100").format("libsvm")
+      .load(path)
+    val row1 = df.first()
+    val v = row1.getAs[SparseVector](1)
+    assert(v == Vectors.sparse(100, Seq((0, 1.0), (2, 2.0), (4, 3.0))))
+  }
+}