Implement ML Features #381. SQLTransformer class and testcase

src/csharp/Microsoft.Spark.E2ETest/IpcTests/ML/Feature/SQLTransformerTests.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using System.Collections.Generic;
+using System.IO;
+using Microsoft.Spark.ML.Feature;
+using Microsoft.Spark.Sql;
+using Microsoft.Spark.Sql.Types;
+using Microsoft.Spark.UnitTest.TestUtils;
+using Xunit;
+
+namespace Microsoft.Spark.E2ETest.IpcTests.ML.Feature
+{
+    [Collection("Spark E2E Tests")]
+    public class SQLTransformerTests : FeatureBaseTests<SQLTransformer>
+    {
+        private readonly SparkSession _spark;
+
+        public SQLTransformerTests(SparkFixture fixture) : base(fixture)
+        {
+            _spark = fixture.Spark;
+        }
+
+        /// <summary>
+        /// Create a <see cref="DataFrame"/>, create a <see cref="SQLTransformer"/> and test the
+        /// available methods.
+        /// </summary>
+        [Fact]
+        public void TestSQLTransformer()
+        {
+            DataFrame input = _spark.CreateDataFrame(
+                new List<GenericRow>
+                {
+                    new GenericRow(new object[] { 0, 1.0, 3.0 }),
+                    new GenericRow(new object[] { 2, 2.0, 5.0 })
+                },
+                new StructType(new List<StructField>
+                {
+                    new StructField("id", new IntegerType()),
+                    new StructField("v1", new DoubleType()),
+                    new StructField("v2", new DoubleType())
+                }));
+
+            string expectedUid = "theUid";
+            string inputStatement = "SELECT *, (v1 + v2) AS v3, (v1 * v2) AS v4 FROM __THIS__";
+
+            SQLTransformer sqlTransformer = new SQLTransformer(expectedUid)
+                .SetStatement(inputStatement);
+
+            string outputStatement = sqlTransformer.GetStatement();
+
+            DataFrame output = sqlTransformer.Transform(input);
+            StructType outputSchema = sqlTransformer.TransformSchema(input.Schema());
+
+            Assert.Contains(output.Schema().Fields, (f => f.Name == "v3"));
+            Assert.Contains(output.Schema().Fields, (f => f.Name == "v4"));
+            Assert.Contains(outputSchema.Fields, (f => f.Name == "v3"));
+            Assert.Contains(outputSchema.Fields, (f => f.Name == "v4"));
+            Assert.Equal(inputStatement, outputStatement);
+
+            using (var tempDirectory = new TemporaryDirectory())
+            {
+                string savePath = Path.Join(tempDirectory.Path, "SQLTransformer");
+                sqlTransformer.Save(savePath);
+
+                SQLTransformer loadedsqlTransformer = SQLTransformer.Load(savePath);
+                Assert.Equal(sqlTransformer.Uid(), loadedsqlTransformer.Uid());
+            }
+            Assert.Equal(expectedUid, sqlTransformer.Uid());
+        }
+    }
+}

src/csharp/Microsoft.Spark/ML/Feature/SQLTransformer.cs

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+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+// See the LICENSE file in the project root for more information.
+
+using Microsoft.Spark.Interop;
+using Microsoft.Spark.Interop.Ipc;
+using Microsoft.Spark.Sql;
+using Microsoft.Spark.Sql.Types;
+
+namespace Microsoft.Spark.ML.Feature
+{
+    /// <summary>
+    /// <see cref="SQLTransformer"/> implements the transformations which are defined by SQL statement.
+    /// </summary>
+    public class SQLTransformer : FeatureBase<SQLTransformer>, IJvmObjectReferenceProvider
+    {
+        private static readonly string s_sqlTransformerClassName = 
+            "org.apache.spark.ml.feature.SQLTransformer";
+
+        /// <summary>
+        /// Create a <see cref="SQLTransformer"/> without any parameters.
+        /// </summary>
+        public SQLTransformer() : base(s_sqlTransformerClassName)
+        {
+        }
+
+        /// <summary>
+        /// Create a <see cref="SQLTransformer"/> with a UID that is used to give the
+        /// <see cref="SQLTransformer"/> a unique ID.
+        /// </summary>
+        /// <param name="uid">An immutable unique ID for the object and its derivatives.</param>
+        public SQLTransformer(string uid) : base(s_sqlTransformerClassName, uid)
+        {
+        }
+
+        internal SQLTransformer(JvmObjectReference jvmObject) : base(jvmObject)
+        {
+        }
+
+        JvmObjectReference IJvmObjectReferenceProvider.Reference => _jvmObject;
+
+        /// <summary>
+        /// Executes the <see cref="SQLTransformer"/> and transforms the DataFrame to include the new
+        /// column.
+        /// </summary>
+        /// <param name="source">The DataFrame to transform</param>
+        /// <returns>
+        /// New <see cref="DataFrame"/> object with the source <see cref="DataFrame"/> transformed.
+        /// </returns>
+        public DataFrame Transform(DataFrame source) =>
+            new DataFrame((JvmObjectReference)_jvmObject.Invoke("transform", source));
+
+        /// <summary>
+        /// Executes the <see cref="SQLTransformer"/> and transforms the schema.
+        /// </summary>
+        /// <param name="value">The Schema to be transformed</param>
+        /// <returns>
+        /// New <see cref="StructType"/> object with the schema <see cref="StructType"/> transformed.
+        /// </returns>
+        public StructType TransformSchema(StructType value) =>
+            new StructType(
+                (JvmObjectReference)_jvmObject.Invoke(
+                    "transformSchema",
+                    DataType.FromJson(_jvmObject.Jvm, value.Json)));
+
+        /// <summary>
+        /// Gets the statement.
+        /// </summary>
+        /// <returns>Statement</returns>
+        public string GetStatement() => (string)_jvmObject.Invoke("getStatement");
+
+        /// <summary>
+        /// Sets the statement to <see cref="SQLTransformer"/>.
+        /// </summary>
+        /// <param name="statement">SQL Statement</param>
+        /// <returns>
+        /// <see cref="SQLTransformer"/> with the statement set.
+        /// </returns>
+        public SQLTransformer SetStatement(string statement) =>
+            WrapAsSQLTransformer((JvmObjectReference)_jvmObject.Invoke("setStatement", statement));
+
+        /// <summary>
+        /// Loads the <see cref="SQLTransformer"/> that was previously saved using Save.
+        /// </summary>
+        /// <param name="path">The path the previous <see cref="SQLTransformer"/> was saved to</param>
+        /// <returns>New <see cref="SQLTransformer"/> object, loaded from path</returns>
+        public static SQLTransformer Load(string path)  =>
+            WrapAsSQLTransformer(
+                SparkEnvironment.JvmBridge.CallStaticJavaMethod(
+                    s_sqlTransformerClassName, 
+                    "load", 
+                    path));
+
+        private static SQLTransformer WrapAsSQLTransformer(object obj) =>
+            new SQLTransformer((JvmObjectReference)obj);
+    }
+}