zhipeng93 commented on code in PR #135:
URL: https://github.com/apache/flink-ml/pull/135#discussion_r935349000


##########
flink-ml-core/src/test/java/org/apache/flink/ml/api/StageTest.java:
##########
@@ -82,6 +85,9 @@ public class StageTest {
         Param<Integer[]> INT_ARRAY_PARAM =
                 new IntArrayParam("intArrayParam", "Description", new 
Integer[] {6, 7});
 
+        Param<Vector> VECTOR_PARAM =

Review Comment:
   nit: How about moving `Vector_PARAM` to the end of function, i.e., Line#121, 
such that we test **all** the ArrayParams and then VectorParams?
   
   Same for other similar cases in Python and Java.



##########
flink-ml-lib/src/main/java/org/apache/flink/ml/feature/elementwiseproduct/ElementwiseProduct.java:
##########
@@ -0,0 +1,112 @@
+/*
+ * 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.flink.ml.feature.elementwiseproduct;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.java.typeutils.RowTypeInfo;
+import org.apache.flink.ml.api.Transformer;
+import org.apache.flink.ml.common.datastream.TableUtils;
+import org.apache.flink.ml.linalg.BLAS;
+import org.apache.flink.ml.linalg.Vector;
+import org.apache.flink.ml.linalg.typeinfo.VectorTypeInfo;
+import org.apache.flink.ml.param.Param;
+import org.apache.flink.ml.util.ParamUtils;
+import org.apache.flink.ml.util.ReadWriteUtils;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import org.apache.flink.table.api.Table;
+import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
+import org.apache.flink.table.api.internal.TableImpl;
+import org.apache.flink.types.Row;
+import org.apache.flink.util.Preconditions;
+
+import org.apache.commons.lang3.ArrayUtils;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * An transformer that multiplies each input vector with a given scaling 
vector using Hadamard

Review Comment:
   nit: To be consistent with the existing java docs, how about make it `A 
Transformer that multiplies...`?



##########
flink-ml-lib/src/test/java/org/apache/flink/ml/feature/ElementwiseProductTest.java:
##########
@@ -0,0 +1,207 @@
+/*
+ * 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.flink.ml.feature;
+
+import org.apache.flink.api.common.restartstrategy.RestartStrategies;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.ml.feature.elementwiseproduct.ElementwiseProduct;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vectors;
+import org.apache.flink.ml.util.TestUtils;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import 
org.apache.flink.streaming.api.environment.ExecutionCheckpointingOptions;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.table.api.Table;
+import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
+import org.apache.flink.test.util.AbstractTestBase;
+import org.apache.flink.types.Row;
+
+import org.apache.commons.collections.IteratorUtils;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+/** Tests {@link ElementwiseProduct}. */
+public class ElementwiseProductTest extends AbstractTestBase {
+
+    private StreamTableEnvironment tEnv;
+    private Table inputDataTable;
+
+    private static final List<Row> INPUT_DATA =
+            Arrays.asList(
+                    Row.of(
+                            0,
+                            Vectors.dense(2.1, 3.1),
+                            Vectors.sparse(5, new int[] {3}, new double[] 
{1.0})),
+                    Row.of(
+                            1,
+                            Vectors.dense(1.1, 3.3),
+                            Vectors.sparse(
+                                    5, new int[] {4, 2, 3, 1}, new double[] 
{4.0, 2.0, 3.0, 1.0})),
+                    Row.of(2, null, null));
+
+    private static final double[] EXPECTED_OUTPUT_DENSE_VEC_ARRAY_1 = new 
double[] {2.31, 3.41};
+    private static final double[] EXPECTED_OUTPUT_DENSE_VEC_ARRAY_2 = new 
double[] {1.21, 3.63};
+
+    private static final int EXPECTED_OUTPUT_SPARSE_VEC_SIZE_1 = 5;
+    private static final int[] EXPECTED_OUTPUT_SPARSE_VEC_INDICES_1 = new 
int[] {3};
+    private static final double[] EXPECTED_OUTPUT_SPARSE_VEC_VALUES_1 = new 
double[] {0.0};
+
+    private static final int EXPECTED_OUTPUT_SPARSE_VEC_SIZE_2 = 5;
+    private static final int[] EXPECTED_OUTPUT_SPARSE_VEC_INDICES_2 = new 
int[] {1, 2, 3, 4};
+    private static final double[] EXPECTED_OUTPUT_SPARSE_VEC_VALUES_2 =
+            new double[] {1.1, 0.0, 0.0, 0.0};
+
+    @Before
+    public void before() {
+        Configuration config = new Configuration();
+        
config.set(ExecutionCheckpointingOptions.ENABLE_CHECKPOINTS_AFTER_TASKS_FINISH, 
true);
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment(config);
+        env.setParallelism(4);
+        env.enableCheckpointing(100);
+        env.setRestartStrategy(RestartStrategies.noRestart());
+        tEnv = StreamTableEnvironment.create(env);
+        DataStream<Row> dataStream = env.fromCollection(INPUT_DATA);
+        inputDataTable = tEnv.fromDataStream(dataStream).as("id", "vec", 
"sparseVec");
+    }
+
+    private void verifyOutputResult(Table output, String outputCol, boolean 
isSparse)
+            throws Exception {
+        DataStream<Row> dataStream = tEnv.toDataStream(output);
+        List<Row> results = 
IteratorUtils.toList(dataStream.executeAndCollect());
+        assertEquals(3, results.size());
+        for (Row result : results) {
+            if (result.getField(0) == (Object) 0) {
+                if (isSparse) {
+                    SparseVector sparseVector = (SparseVector) 
result.getField(outputCol);
+                    assertEquals(EXPECTED_OUTPUT_SPARSE_VEC_SIZE_1, 
sparseVector.size());
+                    assertArrayEquals(EXPECTED_OUTPUT_SPARSE_VEC_INDICES_1, 
sparseVector.indices);
+                    assertArrayEquals(
+                            EXPECTED_OUTPUT_SPARSE_VEC_VALUES_1, 
sparseVector.values, 1.0e-5);
+                } else {
+                    assertArrayEquals(
+                            EXPECTED_OUTPUT_DENSE_VEC_ARRAY_1,
+                            ((DenseVector) result.getField(outputCol)).values,
+                            1.0e-5);
+                }
+            } else if (result.getField(0) == (Object) 1) {
+                if (isSparse) {
+                    SparseVector sparseVector = (SparseVector) 
result.getField(outputCol);
+                    assertEquals(EXPECTED_OUTPUT_SPARSE_VEC_SIZE_2, 
sparseVector.size());
+                    assertArrayEquals(EXPECTED_OUTPUT_SPARSE_VEC_INDICES_2, 
sparseVector.indices);
+                    assertArrayEquals(
+                            EXPECTED_OUTPUT_SPARSE_VEC_VALUES_2, 
sparseVector.values, 1.0e-5);
+                } else {
+                    assertArrayEquals(
+                            EXPECTED_OUTPUT_DENSE_VEC_ARRAY_2,
+                            ((DenseVector) result.getField(outputCol)).values,
+                            1.0e-5);
+                }
+            } else if (result.getField(0) == (Object) 2) {
+                assertNull(result.getField(outputCol));
+            } else {
+                throw new UnsupportedOperationException("Input data id not 
exists.");
+            }
+        }
+    }
+
+    @Test
+    public void testParam() {
+        ElementwiseProduct elementwiseProduct = new ElementwiseProduct();
+        assertEquals("output", elementwiseProduct.getOutputCol());
+        assertEquals("input", elementwiseProduct.getInputCol());
+
+        elementwiseProduct
+                .setInputCol("vec")
+                .setOutputCol("outputVec")
+                .setScalingVec(Vectors.dense(1.0, 2.0, 3.0));
+        assertEquals("vec", elementwiseProduct.getInputCol());
+        assertEquals(Vectors.dense(1.0, 2.0, 3.0), 
elementwiseProduct.getScalingVec());
+        assertEquals("outputVec", elementwiseProduct.getOutputCol());
+    }
+
+    @Test
+    public void testOutputSchema() {
+        ElementwiseProduct elementwiseProduct =
+                new ElementwiseProduct()
+                        .setInputCol("vec")
+                        .setOutputCol("outputVec")
+                        .setScalingVec(Vectors.dense(1.0, 2.0, 3.0));
+        Table output = elementwiseProduct.transform(inputDataTable)[0];
+        assertEquals(
+                Arrays.asList("id", "vec", "sparseVec", "outputVec"),
+                output.getResolvedSchema().getColumnNames());
+    }
+
+    @Test
+    public void testSaveLoadAndTransformDense() throws Exception {
+        ElementwiseProduct elementwiseProduct =
+                new ElementwiseProduct()
+                        .setInputCol("vec")
+                        .setOutputCol("outputVec")
+                        .setScalingVec(Vectors.dense(1.1, 1.1));
+        ElementwiseProduct loadedElementwiseProduct =
+                TestUtils.saveAndReload(
+                        tEnv, elementwiseProduct, 
TEMPORARY_FOLDER.newFolder().getAbsolutePath());
+        Table output = loadedElementwiseProduct.transform(inputDataTable)[0];
+        verifyOutputResult(output, loadedElementwiseProduct.getOutputCol(), 
false);
+    }
+
+    @Test
+    public void testVectorSizeNotEquals() {
+        try {
+            ElementwiseProduct elementwiseProduct =
+                    new ElementwiseProduct()
+                            .setInputCol("vec")
+                            .setOutputCol("outputVec")
+                            .setScalingVec(Vectors.dense(1.1, 1.1, 2.0));
+            Table output = elementwiseProduct.transform(inputDataTable)[0];
+            DataStream<Row> dataStream = tEnv.toDataStream(output);
+            IteratorUtils.toList(dataStream.executeAndCollect());
+            Assert.fail("Expected IllegalArgumentException");

Review Comment:
   It is not an illegalArgumentException here. It is an IllegalState and the 
code never runs here.
   
   How about replace this line with `fail()`?



##########
flink-ml-lib/src/test/java/org/apache/flink/ml/feature/ElementwiseProductTest.java:
##########
@@ -0,0 +1,207 @@
+/*
+ * 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.flink.ml.feature;
+
+import org.apache.flink.api.common.restartstrategy.RestartStrategies;
+import org.apache.flink.configuration.Configuration;
+import org.apache.flink.ml.feature.elementwiseproduct.ElementwiseProduct;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vectors;
+import org.apache.flink.ml.util.TestUtils;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import 
org.apache.flink.streaming.api.environment.ExecutionCheckpointingOptions;
+import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
+import org.apache.flink.table.api.Table;
+import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
+import org.apache.flink.test.util.AbstractTestBase;
+import org.apache.flink.types.Row;
+
+import org.apache.commons.collections.IteratorUtils;
+import org.junit.Assert;
+import org.junit.Before;
+import org.junit.Test;
+
+import java.util.Arrays;
+import java.util.List;
+
+import static org.junit.Assert.assertArrayEquals;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertNull;
+
+/** Tests {@link ElementwiseProduct}. */
+public class ElementwiseProductTest extends AbstractTestBase {
+
+    private StreamTableEnvironment tEnv;
+    private Table inputDataTable;
+
+    private static final List<Row> INPUT_DATA =
+            Arrays.asList(
+                    Row.of(
+                            0,
+                            Vectors.dense(2.1, 3.1),
+                            Vectors.sparse(5, new int[] {3}, new double[] 
{1.0})),
+                    Row.of(
+                            1,
+                            Vectors.dense(1.1, 3.3),
+                            Vectors.sparse(
+                                    5, new int[] {4, 2, 3, 1}, new double[] 
{4.0, 2.0, 3.0, 1.0})),
+                    Row.of(2, null, null));
+
+    private static final double[] EXPECTED_OUTPUT_DENSE_VEC_ARRAY_1 = new 
double[] {2.31, 3.41};
+    private static final double[] EXPECTED_OUTPUT_DENSE_VEC_ARRAY_2 = new 
double[] {1.21, 3.63};
+
+    private static final int EXPECTED_OUTPUT_SPARSE_VEC_SIZE_1 = 5;
+    private static final int[] EXPECTED_OUTPUT_SPARSE_VEC_INDICES_1 = new 
int[] {3};
+    private static final double[] EXPECTED_OUTPUT_SPARSE_VEC_VALUES_1 = new 
double[] {0.0};
+
+    private static final int EXPECTED_OUTPUT_SPARSE_VEC_SIZE_2 = 5;
+    private static final int[] EXPECTED_OUTPUT_SPARSE_VEC_INDICES_2 = new 
int[] {1, 2, 3, 4};
+    private static final double[] EXPECTED_OUTPUT_SPARSE_VEC_VALUES_2 =
+            new double[] {1.1, 0.0, 0.0, 0.0};
+
+    @Before
+    public void before() {
+        Configuration config = new Configuration();
+        
config.set(ExecutionCheckpointingOptions.ENABLE_CHECKPOINTS_AFTER_TASKS_FINISH, 
true);
+        StreamExecutionEnvironment env = 
StreamExecutionEnvironment.getExecutionEnvironment(config);
+        env.setParallelism(4);
+        env.enableCheckpointing(100);
+        env.setRestartStrategy(RestartStrategies.noRestart());
+        tEnv = StreamTableEnvironment.create(env);
+        DataStream<Row> dataStream = env.fromCollection(INPUT_DATA);
+        inputDataTable = tEnv.fromDataStream(dataStream).as("id", "vec", 
"sparseVec");
+    }
+
+    private void verifyOutputResult(Table output, String outputCol, boolean 
isSparse)
+            throws Exception {
+        DataStream<Row> dataStream = tEnv.toDataStream(output);
+        List<Row> results = 
IteratorUtils.toList(dataStream.executeAndCollect());
+        assertEquals(3, results.size());
+        for (Row result : results) {
+            if (result.getField(0) == (Object) 0) {
+                if (isSparse) {
+                    SparseVector sparseVector = (SparseVector) 
result.getField(outputCol);
+                    assertEquals(EXPECTED_OUTPUT_SPARSE_VEC_SIZE_1, 
sparseVector.size());
+                    assertArrayEquals(EXPECTED_OUTPUT_SPARSE_VEC_INDICES_1, 
sparseVector.indices);
+                    assertArrayEquals(
+                            EXPECTED_OUTPUT_SPARSE_VEC_VALUES_1, 
sparseVector.values, 1.0e-5);
+                } else {
+                    assertArrayEquals(
+                            EXPECTED_OUTPUT_DENSE_VEC_ARRAY_1,
+                            ((DenseVector) result.getField(outputCol)).values,
+                            1.0e-5);
+                }
+            } else if (result.getField(0) == (Object) 1) {
+                if (isSparse) {
+                    SparseVector sparseVector = (SparseVector) 
result.getField(outputCol);
+                    assertEquals(EXPECTED_OUTPUT_SPARSE_VEC_SIZE_2, 
sparseVector.size());
+                    assertArrayEquals(EXPECTED_OUTPUT_SPARSE_VEC_INDICES_2, 
sparseVector.indices);
+                    assertArrayEquals(
+                            EXPECTED_OUTPUT_SPARSE_VEC_VALUES_2, 
sparseVector.values, 1.0e-5);
+                } else {
+                    assertArrayEquals(
+                            EXPECTED_OUTPUT_DENSE_VEC_ARRAY_2,
+                            ((DenseVector) result.getField(outputCol)).values,
+                            1.0e-5);
+                }
+            } else if (result.getField(0) == (Object) 2) {
+                assertNull(result.getField(outputCol));
+            } else {
+                throw new UnsupportedOperationException("Input data id not 
exists.");
+            }
+        }
+    }
+
+    @Test
+    public void testParam() {
+        ElementwiseProduct elementwiseProduct = new ElementwiseProduct();
+        assertEquals("output", elementwiseProduct.getOutputCol());
+        assertEquals("input", elementwiseProduct.getInputCol());
+
+        elementwiseProduct
+                .setInputCol("vec")
+                .setOutputCol("outputVec")
+                .setScalingVec(Vectors.dense(1.0, 2.0, 3.0));
+        assertEquals("vec", elementwiseProduct.getInputCol());
+        assertEquals(Vectors.dense(1.0, 2.0, 3.0), 
elementwiseProduct.getScalingVec());
+        assertEquals("outputVec", elementwiseProduct.getOutputCol());
+    }
+
+    @Test
+    public void testOutputSchema() {
+        ElementwiseProduct elementwiseProduct =
+                new ElementwiseProduct()
+                        .setInputCol("vec")
+                        .setOutputCol("outputVec")
+                        .setScalingVec(Vectors.dense(1.0, 2.0, 3.0));
+        Table output = elementwiseProduct.transform(inputDataTable)[0];
+        assertEquals(
+                Arrays.asList("id", "vec", "sparseVec", "outputVec"),
+                output.getResolvedSchema().getColumnNames());
+    }
+
+    @Test
+    public void testSaveLoadAndTransformDense() throws Exception {
+        ElementwiseProduct elementwiseProduct =
+                new ElementwiseProduct()
+                        .setInputCol("vec")
+                        .setOutputCol("outputVec")
+                        .setScalingVec(Vectors.dense(1.1, 1.1));
+        ElementwiseProduct loadedElementwiseProduct =
+                TestUtils.saveAndReload(
+                        tEnv, elementwiseProduct, 
TEMPORARY_FOLDER.newFolder().getAbsolutePath());
+        Table output = loadedElementwiseProduct.transform(inputDataTable)[0];
+        verifyOutputResult(output, loadedElementwiseProduct.getOutputCol(), 
false);
+    }
+
+    @Test
+    public void testVectorSizeNotEquals() {
+        try {
+            ElementwiseProduct elementwiseProduct =
+                    new ElementwiseProduct()
+                            .setInputCol("vec")
+                            .setOutputCol("outputVec")
+                            .setScalingVec(Vectors.dense(1.1, 1.1, 2.0));
+            Table output = elementwiseProduct.transform(inputDataTable)[0];
+            DataStream<Row> dataStream = tEnv.toDataStream(output);
+            IteratorUtils.toList(dataStream.executeAndCollect());
+            Assert.fail("Expected IllegalArgumentException");
+        } catch (Exception e) {
+            assertEquals(
+                    "Vector size mismatched.",
+                    
e.getCause().getCause().getCause().getCause().getCause().getMessage());

Review Comment:
   How about using `ExceptionUtils.getRootCause(e).getMessage())`?



##########
flink-ml-lib/src/main/java/org/apache/flink/ml/feature/elementwiseproduct/ElementwiseProduct.java:
##########
@@ -0,0 +1,112 @@
+/*
+ * 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.flink.ml.feature.elementwiseproduct;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.java.typeutils.RowTypeInfo;
+import org.apache.flink.ml.api.Transformer;
+import org.apache.flink.ml.common.datastream.TableUtils;
+import org.apache.flink.ml.linalg.BLAS;
+import org.apache.flink.ml.linalg.Vector;
+import org.apache.flink.ml.linalg.typeinfo.VectorTypeInfo;
+import org.apache.flink.ml.param.Param;
+import org.apache.flink.ml.util.ParamUtils;
+import org.apache.flink.ml.util.ReadWriteUtils;
+import org.apache.flink.streaming.api.datastream.DataStream;
+import org.apache.flink.table.api.Table;
+import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
+import org.apache.flink.table.api.internal.TableImpl;
+import org.apache.flink.types.Row;
+import org.apache.flink.util.Preconditions;
+
+import org.apache.commons.lang3.ArrayUtils;
+
+import java.io.IOException;
+import java.util.HashMap;
+import java.util.Map;
+
+/**
+ * An transformer that multiplies each input vector with a given scaling 
vector using Hadamard
+ * product.
+ *
+ * <p>If the size of the input vector does not equal the size of the scaling 
vector, the transformer
+ * will throw {@link IllegalArgumentException}.
+ */
+public class ElementwiseProduct
+        implements Transformer<ElementwiseProduct>, 
ElementwiseProductParams<ElementwiseProduct> {
+    private final Map<Param<?>, Object> paramMap = new HashMap<>();
+
+    public ElementwiseProduct() {
+        ParamUtils.initializeMapWithDefaultValues(paramMap, this);
+    }
+
+    @Override
+    public Table[] transform(Table... inputs) {
+        Preconditions.checkArgument(inputs.length == 1);
+        StreamTableEnvironment tEnv =
+                (StreamTableEnvironment) ((TableImpl) 
inputs[0]).getTableEnvironment();
+        RowTypeInfo inputTypeInfo = 
TableUtils.getRowTypeInfo(inputs[0].getResolvedSchema());
+        RowTypeInfo outputTypeInfo =
+                new RowTypeInfo(
+                        ArrayUtils.addAll(inputTypeInfo.getFieldTypes(), 
VectorTypeInfo.INSTANCE),
+                        ArrayUtils.addAll(inputTypeInfo.getFieldNames(), 
getOutputCol()));
+        DataStream<Row> output =
+                tEnv.toDataStream(inputs[0])
+                        .map(
+                                new ElementwiseProductFunction(getInputCol(), 
getScalingVec()),
+                                outputTypeInfo);
+        Table outputTable = tEnv.fromDataStream(output);
+        return new Table[] {outputTable};
+    }
+
+    private static class ElementwiseProductFunction implements 
MapFunction<Row, Row> {
+        private final String inputCol;
+        private final Vector scalingVec;
+
+        public ElementwiseProductFunction(String inputCol, Vector scalingVec) {
+            this.inputCol = inputCol;
+            this.scalingVec = scalingVec;
+        }
+
+        @Override
+        public Row map(Row value) {
+            Vector inputVec = value.getFieldAs(inputCol);
+            Vector retVec = (null != inputVec) ? inputVec.clone() : null;

Review Comment:
   How about we check the size of the inputVec and the scaling vec before 
conducting `hdot`? Then we can throw an illegalArgumentException here and the 
exception seems more clear to me.



##########
flink-ml-python/pyflink/ml/lib/feature/elementwiseproduct.py:
##########
@@ -0,0 +1,73 @@
+################################################################################
+#  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.
+################################################################################
+
+from pyflink.ml.core.param import ParamValidators, Param, VectorParam
+from pyflink.ml.core.wrapper import JavaWithParams
+from pyflink.ml.lib.feature.common import JavaFeatureTransformer
+from pyflink.ml.lib.param import HasInputCol, HasOutputCol
+from pyflink.ml.core.linalg import Vector
+
+
+class _ElementwiseProductParams(
+    JavaWithParams,
+    HasInputCol,
+    HasOutputCol
+):
+    """
+    Params for :class:`ElementwiseProduct`.
+    """
+
+    SCALING_VEC: Param[Vector] = VectorParam(
+        "scaling_vec",
+        "the scaling vector to multiply with input vectors using hadamard 
product.",
+        None,
+        ParamValidators.not_null())
+
+    def __init__(self, java_params):
+        super(_ElementwiseProductParams, self).__init__(java_params)
+
+    def set_scaling_vec(self, value: Vector):
+        return self.set(self.SCALING_VEC, value)
+
+    def get_scaling_vec(self) -> Vector:
+        return self.get(self.SCALING_VEC)
+
+    @property
+    def scaling_vec(self) -> Vector:
+        return self.get_scaling_vec()
+
+
+class ElementwiseProduct(JavaFeatureTransformer, _ElementwiseProductParams):
+    """
+    ElementwiseProduct is a transformer that multiplies each input vector with 
a

Review Comment:
   nit: make the python doc consistent with java docs.



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