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Posted to issues@flink.apache.org by GitBox <gi...@apache.org> on 2022/04/01 11:24:21 UTC

[GitHub] [flink-ml] lindong28 commented on a change in pull request #56: [FLINK-25616] Add Transformer for VectorAssembler

lindong28 commented on a change in pull request #56:
URL: https://github.com/apache/flink-ml/pull/56#discussion_r840443219



##########
File path: flink-ml-lib/src/main/java/org/apache/flink/ml/feature/vectorassembler/VectorAssembler.java
##########
@@ -0,0 +1,179 @@
+/*
+ * 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.vectorassembler;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vector;
+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.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Vector assembler is a transformer that combines a given list of columns into a single vector

Review comment:
       Other Transformer subclasses' Java docs typically start with `e.g. A model...`. And the sentence `It will combine raw features and features generated` seems a little bit redundant.
   
   Would the following Java doc be simpler?
   
   ```
   /**
    * A feature transformer that combines a given list of input columns into a vector column. Types of
    * input columns must be either vector or numerical value.
    */
   ```

##########
File path: flink-ml-lib/src/main/java/org/apache/flink/ml/feature/vectorassembler/VectorAssembler.java
##########
@@ -0,0 +1,179 @@
+/*
+ * 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.vectorassembler;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vector;
+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.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Vector assembler is a transformer that combines a given list of columns into a single vector
+ * column. It will combine raw features and features generated by different feature transformers
+ * into a single feature vector. The input features of this transformer must be a vector feature or
+ * a numerical feature.
+ */
+public class VectorAssembler
+        implements Transformer<VectorAssembler>, VectorAssemblerParams<VectorAssembler> {
+    private final Map<Param<?>, Object> paramMap = new HashMap<>();
+    private static final double RATIO = 1.5;
+
+    public VectorAssembler() {
+        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(), TypeInformation.of(Vector.class)),
+                        ArrayUtils.addAll(inputTypeInfo.getFieldNames(), getOutputCol()));
+        DataStream<Row> output =
+                tEnv.toDataStream(inputs[0])
+                        .map(new AssemblerFunc(getInputCols(), getHandleInvalid()), outputTypeInfo);
+        Table outputTable = tEnv.fromDataStream(output);
+        return new Table[] {outputTable};
+    }
+
+    private static class AssemblerFunc implements MapFunction<Row, Row> {
+        private final String[] inputCols;
+        private final String handleInvalid;
+
+        public AssemblerFunc(String[] inputCols, String handleInvalid) {
+            this.inputCols = inputCols;
+            this.handleInvalid = handleInvalid;
+        }
+
+        @Override
+        public Row map(Row value) {
+            Object[] objects = new Object[inputCols.length];
+            for (int i = 0; i < objects.length; ++i) {
+                objects[i] = value.getField(inputCols[i]);
+            }
+            return Row.join(value, Row.of(assemble(objects, handleInvalid)));
+        }
+    }
+
+    @Override
+    public void save(String path) throws IOException {
+        ReadWriteUtils.saveMetadata(this, path);
+    }
+
+    public static VectorAssembler load(StreamTableEnvironment env, String path) throws IOException {
+        return ReadWriteUtils.loadStageParam(path);
+    }
+
+    @Override
+    public Map<Param<?>, Object> getParamMap() {
+        return paramMap;
+    }
+
+    private static Vector assemble(Object[] objects, String handleInvalid) {
+        int offset = 0;
+        Map<Integer, Double> map = new LinkedHashMap<>(objects.length);
+        for (Object object : objects) {
+            try {
+                Preconditions.checkNotNull(object, "VectorAssembler Error: input data is null.");
+                if (object instanceof Number) {
+                    map.put(offset++, ((Number) object).doubleValue());
+                } else if (object instanceof Vector) {
+                    offset = appendVector((Vector) object, map, offset);
+                } else {
+                    throw new UnsupportedOperationException(
+                            "Vector assembler : input type has not been supported yet.");
+                }
+            } catch (Exception e) {
+                switch (handleInvalid) {
+                    case HasHandleInvalid.ERROR_INVALID:
+                        throw new RuntimeException("Vector assembler failed.", e);
+                    case HasHandleInvalid.SKIP_INVALID:
+                        return null;
+                    default:
+                }
+            }
+        }
+
+        if (map.size() * RATIO > offset) {
+            DenseVector assembledVector = new DenseVector(offset);
+            for (int key : map.keySet()) {
+                assembledVector.values[key] = map.get(key);
+            }
+            return assembledVector;
+        } else {
+            return convertMapToSparseVector(offset, map);
+        }
+    }
+
+    private static int appendVector(Vector vec, Map<Integer, Double> map, int offset) {
+        if (vec instanceof SparseVector) {
+            SparseVector sparseVector = (SparseVector) vec;
+            int[] indices = sparseVector.indices;
+            double[] values = sparseVector.values;
+            for (int j = 0; j < indices.length; ++j) {
+                map.put(offset + indices[j], values[j]);
+            }
+            offset += sparseVector.size();
+        } else if (vec instanceof DenseVector) {

Review comment:
       Would it be simpler to just do `else {...}`?

##########
File path: flink-ml-lib/src/test/java/org/apache/flink/ml/feature/VectorAssemblerTest.java
##########
@@ -0,0 +1,175 @@
+/*
+ * 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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.feature.vectorassembler.VectorAssembler;
+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.StageTestUtils;
+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.DataTypes;
+import org.apache.flink.table.api.Schema;
+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 VectorAssembler. */
+public class VectorAssemblerTest 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),
+                            1.0,
+                            Vectors.sparse(5, new int[] {3}, new double[] {1.0})),
+                    Row.of(
+                            1,
+                            Vectors.dense(2.1, 3.1),
+                            1.0,
+                            Vectors.sparse(
+                                    5, new int[] {4, 2, 3, 1}, new double[] {4.0, 2.0, 3.0, 1.0})),
+                    Row.of(2, null, 1.0, null));
+
+    private static final SparseVector EXPECTED_DATA_1 =

Review comment:
       nits: To be more consistent with `INPUT_DATA`, how about renaming it as `EXPECTED_OUTPUT_DATA_1`?

##########
File path: flink-ml-lib/src/test/java/org/apache/flink/ml/feature/VectorAssemblerTest.java
##########
@@ -0,0 +1,175 @@
+/*
+ * 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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.feature.vectorassembler.VectorAssembler;
+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.StageTestUtils;
+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.DataTypes;
+import org.apache.flink.table.api.Schema;
+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 VectorAssembler. */
+public class VectorAssemblerTest 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),
+                            1.0,
+                            Vectors.sparse(5, new int[] {3}, new double[] {1.0})),
+                    Row.of(
+                            1,
+                            Vectors.dense(2.1, 3.1),
+                            1.0,
+                            Vectors.sparse(
+                                    5, new int[] {4, 2, 3, 1}, new double[] {4.0, 2.0, 3.0, 1.0})),
+                    Row.of(2, null, 1.0, null));
+
+    private static final SparseVector EXPECTED_DATA_1 =
+            Vectors.sparse(8, new int[] {0, 1, 2, 6}, new double[] {2.1, 3.1, 1.0, 1.0});
+    private static final DenseVector EXPECTED_DATA_2 =
+            Vectors.dense(2.1, 3.1, 1.0, 0.0, 1.0, 2.0, 3.0, 4.0);
+
+    @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);
+        Schema schema =
+                Schema.newBuilder()
+                        .column("f0", DataTypes.INT())
+                        .column("f1", DataTypes.of(DenseVector.class))
+                        .column("f2", DataTypes.DOUBLE())
+                        .column("f3", DataTypes.of(SparseVector.class))
+                        .build();
+        DataStream<Row> dataStream = env.fromCollection(INPUT_DATA);
+        inputDataTable =

Review comment:
       We can just do the following without using `schema`.
   
   ```
   inputDataTable = tEnv.fromDataStream(dataStream).as("id", "vec", "num", "sparseVec")
   ```

##########
File path: flink-ml-lib/src/main/java/org/apache/flink/ml/feature/vectorassembler/VectorAssembler.java
##########
@@ -0,0 +1,179 @@
+/*
+ * 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.vectorassembler;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vector;
+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.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Vector assembler is a transformer that combines a given list of columns into a single vector
+ * column. It will combine raw features and features generated by different feature transformers
+ * into a single feature vector. The input features of this transformer must be a vector feature or
+ * a numerical feature.
+ */
+public class VectorAssembler
+        implements Transformer<VectorAssembler>, VectorAssemblerParams<VectorAssembler> {
+    private final Map<Param<?>, Object> paramMap = new HashMap<>();
+    private static final double RATIO = 1.5;
+
+    public VectorAssembler() {
+        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(), TypeInformation.of(Vector.class)),
+                        ArrayUtils.addAll(inputTypeInfo.getFieldNames(), getOutputCol()));
+        DataStream<Row> output =
+                tEnv.toDataStream(inputs[0])
+                        .map(new AssemblerFunc(getInputCols(), getHandleInvalid()), outputTypeInfo);
+        Table outputTable = tEnv.fromDataStream(output);
+        return new Table[] {outputTable};
+    }
+
+    private static class AssemblerFunc implements MapFunction<Row, Row> {
+        private final String[] inputCols;
+        private final String handleInvalid;
+
+        public AssemblerFunc(String[] inputCols, String handleInvalid) {
+            this.inputCols = inputCols;
+            this.handleInvalid = handleInvalid;
+        }
+
+        @Override
+        public Row map(Row value) {
+            Object[] objects = new Object[inputCols.length];
+            for (int i = 0; i < objects.length; ++i) {
+                objects[i] = value.getField(inputCols[i]);
+            }
+            return Row.join(value, Row.of(assemble(objects, handleInvalid)));
+        }
+    }
+
+    @Override
+    public void save(String path) throws IOException {
+        ReadWriteUtils.saveMetadata(this, path);
+    }
+
+    public static VectorAssembler load(StreamTableEnvironment env, String path) throws IOException {
+        return ReadWriteUtils.loadStageParam(path);
+    }
+
+    @Override
+    public Map<Param<?>, Object> getParamMap() {
+        return paramMap;
+    }
+
+    private static Vector assemble(Object[] objects, String handleInvalid) {
+        int offset = 0;
+        Map<Integer, Double> map = new LinkedHashMap<>(objects.length);
+        for (Object object : objects) {
+            try {
+                Preconditions.checkNotNull(object, "VectorAssembler Error: input data is null.");
+                if (object instanceof Number) {
+                    map.put(offset++, ((Number) object).doubleValue());
+                } else if (object instanceof Vector) {
+                    offset = appendVector((Vector) object, map, offset);
+                } else {
+                    throw new UnsupportedOperationException(
+                            "Vector assembler : input type has not been supported yet.");
+                }
+            } catch (Exception e) {
+                switch (handleInvalid) {
+                    case HasHandleInvalid.ERROR_INVALID:
+                        throw new RuntimeException("Vector assembler failed.", e);
+                    case HasHandleInvalid.SKIP_INVALID:
+                        return null;

Review comment:
       In this case, the returned table will contain a row whose outputColumn value is null. This sounds like `keep` instead of `skip`. Spark uses `keep` as the skip_invalid param value in this case.
   
   Should we add a `keep` option in `HasHandleInvalid`? 

##########
File path: flink-ml-lib/src/main/java/org/apache/flink/ml/feature/vectorassembler/VectorAssembler.java
##########
@@ -0,0 +1,179 @@
+/*
+ * 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.vectorassembler;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vector;
+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.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Vector assembler is a transformer that combines a given list of columns into a single vector
+ * column. It will combine raw features and features generated by different feature transformers
+ * into a single feature vector. The input features of this transformer must be a vector feature or
+ * a numerical feature.
+ */
+public class VectorAssembler
+        implements Transformer<VectorAssembler>, VectorAssemblerParams<VectorAssembler> {
+    private final Map<Param<?>, Object> paramMap = new HashMap<>();
+    private static final double RATIO = 1.5;
+
+    public VectorAssembler() {
+        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(), TypeInformation.of(Vector.class)),
+                        ArrayUtils.addAll(inputTypeInfo.getFieldNames(), getOutputCol()));
+        DataStream<Row> output =
+                tEnv.toDataStream(inputs[0])
+                        .map(new AssemblerFunc(getInputCols(), getHandleInvalid()), outputTypeInfo);
+        Table outputTable = tEnv.fromDataStream(output);
+        return new Table[] {outputTable};
+    }
+
+    private static class AssemblerFunc implements MapFunction<Row, Row> {
+        private final String[] inputCols;
+        private final String handleInvalid;
+
+        public AssemblerFunc(String[] inputCols, String handleInvalid) {
+            this.inputCols = inputCols;
+            this.handleInvalid = handleInvalid;
+        }
+
+        @Override
+        public Row map(Row value) {
+            Object[] objects = new Object[inputCols.length];
+            for (int i = 0; i < objects.length; ++i) {
+                objects[i] = value.getField(inputCols[i]);
+            }
+            return Row.join(value, Row.of(assemble(objects, handleInvalid)));
+        }
+    }
+
+    @Override
+    public void save(String path) throws IOException {
+        ReadWriteUtils.saveMetadata(this, path);
+    }
+
+    public static VectorAssembler load(StreamTableEnvironment env, String path) throws IOException {
+        return ReadWriteUtils.loadStageParam(path);
+    }
+
+    @Override
+    public Map<Param<?>, Object> getParamMap() {
+        return paramMap;
+    }
+
+    private static Vector assemble(Object[] objects, String handleInvalid) {
+        int offset = 0;
+        Map<Integer, Double> map = new LinkedHashMap<>(objects.length);
+        for (Object object : objects) {
+            try {
+                Preconditions.checkNotNull(object, "VectorAssembler Error: input data is null.");
+                if (object instanceof Number) {
+                    map.put(offset++, ((Number) object).doubleValue());
+                } else if (object instanceof Vector) {
+                    offset = appendVector((Vector) object, map, offset);
+                } else {
+                    throw new UnsupportedOperationException(

Review comment:
       Should it be `IllegalArgumentException`?
   
   And we probably don't need to explicitly specify `Vector assembler` in the error message since the stracktrace should already contain this information.

##########
File path: flink-ml-lib/src/main/java/org/apache/flink/ml/feature/vectorassembler/VectorAssembler.java
##########
@@ -0,0 +1,179 @@
+/*
+ * 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.vectorassembler;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vector;
+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.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Vector assembler is a transformer that combines a given list of columns into a single vector
+ * column. It will combine raw features and features generated by different feature transformers
+ * into a single feature vector. The input features of this transformer must be a vector feature or
+ * a numerical feature.
+ */
+public class VectorAssembler
+        implements Transformer<VectorAssembler>, VectorAssemblerParams<VectorAssembler> {
+    private final Map<Param<?>, Object> paramMap = new HashMap<>();
+    private static final double RATIO = 1.5;
+
+    public VectorAssembler() {
+        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(), TypeInformation.of(Vector.class)),
+                        ArrayUtils.addAll(inputTypeInfo.getFieldNames(), getOutputCol()));
+        DataStream<Row> output =
+                tEnv.toDataStream(inputs[0])
+                        .map(new AssemblerFunc(getInputCols(), getHandleInvalid()), outputTypeInfo);
+        Table outputTable = tEnv.fromDataStream(output);
+        return new Table[] {outputTable};
+    }
+
+    private static class AssemblerFunc implements MapFunction<Row, Row> {
+        private final String[] inputCols;
+        private final String handleInvalid;
+
+        public AssemblerFunc(String[] inputCols, String handleInvalid) {
+            this.inputCols = inputCols;
+            this.handleInvalid = handleInvalid;
+        }
+
+        @Override
+        public Row map(Row value) {
+            Object[] objects = new Object[inputCols.length];
+            for (int i = 0; i < objects.length; ++i) {
+                objects[i] = value.getField(inputCols[i]);
+            }
+            return Row.join(value, Row.of(assemble(objects, handleInvalid)));
+        }
+    }
+
+    @Override
+    public void save(String path) throws IOException {
+        ReadWriteUtils.saveMetadata(this, path);
+    }
+
+    public static VectorAssembler load(StreamTableEnvironment env, String path) throws IOException {
+        return ReadWriteUtils.loadStageParam(path);
+    }
+
+    @Override
+    public Map<Param<?>, Object> getParamMap() {
+        return paramMap;
+    }
+
+    private static Vector assemble(Object[] objects, String handleInvalid) {
+        int offset = 0;
+        Map<Integer, Double> map = new LinkedHashMap<>(objects.length);
+        for (Object object : objects) {
+            try {
+                Preconditions.checkNotNull(object, "VectorAssembler Error: input data is null.");
+                if (object instanceof Number) {
+                    map.put(offset++, ((Number) object).doubleValue());
+                } else if (object instanceof Vector) {
+                    offset = appendVector((Vector) object, map, offset);
+                } else {
+                    throw new UnsupportedOperationException(
+                            "Vector assembler : input type has not been supported yet.");
+                }
+            } catch (Exception e) {
+                switch (handleInvalid) {
+                    case HasHandleInvalid.ERROR_INVALID:
+                        throw new RuntimeException("Vector assembler failed.", e);
+                    case HasHandleInvalid.SKIP_INVALID:
+                        return null;
+                    default:
+                }
+            }
+        }
+
+        if (map.size() * RATIO > offset) {
+            DenseVector assembledVector = new DenseVector(offset);
+            for (int key : map.keySet()) {
+                assembledVector.values[key] = map.get(key);
+            }
+            return assembledVector;
+        } else {
+            return convertMapToSparseVector(offset, map);
+        }
+    }
+
+    private static int appendVector(Vector vec, Map<Integer, Double> map, int offset) {
+        if (vec instanceof SparseVector) {
+            SparseVector sparseVector = (SparseVector) vec;
+            int[] indices = sparseVector.indices;
+            double[] values = sparseVector.values;
+            for (int j = 0; j < indices.length; ++j) {
+                map.put(offset + indices[j], values[j]);
+            }
+            offset += sparseVector.size();
+        } else if (vec instanceof DenseVector) {
+            DenseVector denseVector = (DenseVector) vec;
+            for (int j = 0; j < denseVector.size(); ++j) {
+                map.put(offset++, denseVector.values[j]);
+            }
+        }
+        return offset;
+    }
+
+    private static SparseVector convertMapToSparseVector(int size, Map<Integer, Double> map) {
+        int nnz = map.size();

Review comment:
       It is not obvious what `nnz` means. 
   
   Would it be more self-explanatory to rename it as `map_size`? It could be even simpler to do the following:
   
   ```
   int[] indices = new int[map.size()];
   double[] values = new double[map.size()];
   ```

##########
File path: flink-ml-lib/src/main/java/org/apache/flink/ml/feature/vectorassembler/VectorAssembler.java
##########
@@ -0,0 +1,179 @@
+/*
+ * 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.vectorassembler;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vector;
+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.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Vector assembler is a transformer that combines a given list of columns into a single vector
+ * column. It will combine raw features and features generated by different feature transformers
+ * into a single feature vector. The input features of this transformer must be a vector feature or
+ * a numerical feature.
+ */
+public class VectorAssembler
+        implements Transformer<VectorAssembler>, VectorAssemblerParams<VectorAssembler> {
+    private final Map<Param<?>, Object> paramMap = new HashMap<>();
+    private static final double RATIO = 1.5;
+
+    public VectorAssembler() {
+        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(), TypeInformation.of(Vector.class)),
+                        ArrayUtils.addAll(inputTypeInfo.getFieldNames(), getOutputCol()));
+        DataStream<Row> output =
+                tEnv.toDataStream(inputs[0])
+                        .map(new AssemblerFunc(getInputCols(), getHandleInvalid()), outputTypeInfo);
+        Table outputTable = tEnv.fromDataStream(output);
+        return new Table[] {outputTable};
+    }
+
+    private static class AssemblerFunc implements MapFunction<Row, Row> {
+        private final String[] inputCols;
+        private final String handleInvalid;
+
+        public AssemblerFunc(String[] inputCols, String handleInvalid) {
+            this.inputCols = inputCols;
+            this.handleInvalid = handleInvalid;
+        }
+
+        @Override
+        public Row map(Row value) {
+            Object[] objects = new Object[inputCols.length];
+            for (int i = 0; i < objects.length; ++i) {
+                objects[i] = value.getField(inputCols[i]);
+            }
+            return Row.join(value, Row.of(assemble(objects, handleInvalid)));
+        }
+    }
+
+    @Override
+    public void save(String path) throws IOException {
+        ReadWriteUtils.saveMetadata(this, path);
+    }
+
+    public static VectorAssembler load(StreamTableEnvironment env, String path) throws IOException {
+        return ReadWriteUtils.loadStageParam(path);
+    }
+
+    @Override
+    public Map<Param<?>, Object> getParamMap() {
+        return paramMap;
+    }
+
+    private static Vector assemble(Object[] objects, String handleInvalid) {
+        int offset = 0;
+        Map<Integer, Double> map = new LinkedHashMap<>(objects.length);
+        for (Object object : objects) {
+            try {
+                Preconditions.checkNotNull(object, "VectorAssembler Error: input data is null.");
+                if (object instanceof Number) {
+                    map.put(offset++, ((Number) object).doubleValue());
+                } else if (object instanceof Vector) {
+                    offset = appendVector((Vector) object, map, offset);
+                } else {
+                    throw new UnsupportedOperationException(
+                            "Vector assembler : input type has not been supported yet.");
+                }
+            } catch (Exception e) {
+                switch (handleInvalid) {
+                    case HasHandleInvalid.ERROR_INVALID:
+                        throw new RuntimeException("Vector assembler failed.", e);
+                    case HasHandleInvalid.SKIP_INVALID:
+                        return null;
+                    default:
+                }
+            }
+        }
+
+        if (map.size() * RATIO > offset) {
+            DenseVector assembledVector = new DenseVector(offset);
+            for (int key : map.keySet()) {
+                assembledVector.values[key] = map.get(key);
+            }
+            return assembledVector;
+        } else {
+            return convertMapToSparseVector(offset, map);
+        }
+    }
+
+    private static int appendVector(Vector vec, Map<Integer, Double> map, int offset) {
+        if (vec instanceof SparseVector) {
+            SparseVector sparseVector = (SparseVector) vec;
+            int[] indices = sparseVector.indices;
+            double[] values = sparseVector.values;
+            for (int j = 0; j < indices.length; ++j) {
+                map.put(offset + indices[j], values[j]);
+            }
+            offset += sparseVector.size();
+        } else if (vec instanceof DenseVector) {
+            DenseVector denseVector = (DenseVector) vec;
+            for (int j = 0; j < denseVector.size(); ++j) {

Review comment:
       nits: Could we use `for (int i = 0; i < indices.length; i++)` to be consistent with other for loop code style?

##########
File path: flink-ml-lib/src/test/java/org/apache/flink/ml/feature/VectorAssemblerTest.java
##########
@@ -0,0 +1,175 @@
+/*
+ * 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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.feature.vectorassembler.VectorAssembler;
+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.StageTestUtils;
+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.DataTypes;
+import org.apache.flink.table.api.Schema;
+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 VectorAssembler. */
+public class VectorAssemblerTest 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),
+                            1.0,
+                            Vectors.sparse(5, new int[] {3}, new double[] {1.0})),
+                    Row.of(
+                            1,
+                            Vectors.dense(2.1, 3.1),
+                            1.0,
+                            Vectors.sparse(
+                                    5, new int[] {4, 2, 3, 1}, new double[] {4.0, 2.0, 3.0, 1.0})),
+                    Row.of(2, null, 1.0, null));
+
+    private static final SparseVector EXPECTED_DATA_1 =
+            Vectors.sparse(8, new int[] {0, 1, 2, 6}, new double[] {2.1, 3.1, 1.0, 1.0});
+    private static final DenseVector EXPECTED_DATA_2 =
+            Vectors.dense(2.1, 3.1, 1.0, 0.0, 1.0, 2.0, 3.0, 4.0);
+
+    @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);
+        Schema schema =
+                Schema.newBuilder()
+                        .column("f0", DataTypes.INT())
+                        .column("f1", DataTypes.of(DenseVector.class))
+                        .column("f2", DataTypes.DOUBLE())
+                        .column("f3", DataTypes.of(SparseVector.class))
+                        .build();
+        DataStream<Row> dataStream = env.fromCollection(INPUT_DATA);
+        inputDataTable =
+                tEnv.fromDataStream(dataStream, schema).as("id", "vec", "num", "sparseVec");
+    }
+
+    private void verifyOutputResult(Table output, String outputCol) 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) {
+                assertEquals(EXPECTED_DATA_1, result.getField(outputCol));
+            } else if (result.getField(0) == (Object) 1) {
+                assertEquals(EXPECTED_DATA_2, result.getField(outputCol));
+            } else {
+                assertNull(result.getField(outputCol));
+            }
+        }
+    }
+
+    @Test
+    public void testParam() {
+        VectorAssembler vectorAssembler = new VectorAssembler();
+        assertEquals(HasHandleInvalid.ERROR_INVALID, vectorAssembler.getHandleInvalid());
+        assertEquals("output", vectorAssembler.getOutputCol());
+        vectorAssembler
+                .setInputCols("vec", "num", "sparseVec")
+                .setOutputCol("assembledVec")
+                .setHandleInvalid(HasHandleInvalid.SKIP_INVALID);
+        assertArrayEquals(new String[] {"vec", "num", "sparseVec"}, vectorAssembler.getInputCols());
+        assertEquals(HasHandleInvalid.SKIP_INVALID, vectorAssembler.getHandleInvalid());
+        assertEquals("assembledVec", vectorAssembler.getOutputCol());
+    }
+
+    @Test
+    public void testTransform() throws Exception {
+        VectorAssembler vectorAssembler =
+                new VectorAssembler()
+                        .setInputCols("vec", "num", "sparseVec")
+                        .setOutputCol("assembledVec")
+                        .setHandleInvalid(HasHandleInvalid.SKIP_INVALID);
+        Table output = vectorAssembler.transform(inputDataTable)[0];

Review comment:
       Could we also test the schema of the output table, similar to what we did in `KMeansTest::testFitAndPredict()`?

##########
File path: flink-ml-lib/src/main/java/org/apache/flink/ml/feature/vectorassembler/VectorAssembler.java
##########
@@ -0,0 +1,179 @@
+/*
+ * 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.vectorassembler;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vector;
+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.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Vector assembler is a transformer that combines a given list of columns into a single vector
+ * column. It will combine raw features and features generated by different feature transformers
+ * into a single feature vector. The input features of this transformer must be a vector feature or
+ * a numerical feature.
+ */
+public class VectorAssembler
+        implements Transformer<VectorAssembler>, VectorAssemblerParams<VectorAssembler> {
+    private final Map<Param<?>, Object> paramMap = new HashMap<>();
+    private static final double RATIO = 1.5;
+
+    public VectorAssembler() {
+        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(), TypeInformation.of(Vector.class)),
+                        ArrayUtils.addAll(inputTypeInfo.getFieldNames(), getOutputCol()));
+        DataStream<Row> output =
+                tEnv.toDataStream(inputs[0])
+                        .map(new AssemblerFunc(getInputCols(), getHandleInvalid()), outputTypeInfo);
+        Table outputTable = tEnv.fromDataStream(output);
+        return new Table[] {outputTable};
+    }
+
+    private static class AssemblerFunc implements MapFunction<Row, Row> {
+        private final String[] inputCols;
+        private final String handleInvalid;
+
+        public AssemblerFunc(String[] inputCols, String handleInvalid) {
+            this.inputCols = inputCols;
+            this.handleInvalid = handleInvalid;
+        }
+
+        @Override
+        public Row map(Row value) {
+            Object[] objects = new Object[inputCols.length];
+            for (int i = 0; i < objects.length; ++i) {
+                objects[i] = value.getField(inputCols[i]);
+            }
+            return Row.join(value, Row.of(assemble(objects, handleInvalid)));
+        }
+    }
+
+    @Override
+    public void save(String path) throws IOException {
+        ReadWriteUtils.saveMetadata(this, path);
+    }
+
+    public static VectorAssembler load(StreamTableEnvironment env, String path) throws IOException {
+        return ReadWriteUtils.loadStageParam(path);
+    }
+
+    @Override
+    public Map<Param<?>, Object> getParamMap() {
+        return paramMap;
+    }
+
+    private static Vector assemble(Object[] objects, String handleInvalid) {
+        int offset = 0;
+        Map<Integer, Double> map = new LinkedHashMap<>(objects.length);
+        for (Object object : objects) {
+            try {
+                Preconditions.checkNotNull(object, "VectorAssembler Error: input data is null.");
+                if (object instanceof Number) {
+                    map.put(offset++, ((Number) object).doubleValue());
+                } else if (object instanceof Vector) {
+                    offset = appendVector((Vector) object, map, offset);
+                } else {
+                    throw new UnsupportedOperationException(
+                            "Vector assembler : input type has not been supported yet.");
+                }
+            } catch (Exception e) {
+                switch (handleInvalid) {
+                    case HasHandleInvalid.ERROR_INVALID:
+                        throw new RuntimeException("Vector assembler failed.", e);

Review comment:
       Would it be simpler to just do `throw e` here?

##########
File path: flink-ml-lib/src/main/java/org/apache/flink/ml/feature/vectorassembler/VectorAssembler.java
##########
@@ -0,0 +1,179 @@
+/*
+ * 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.vectorassembler;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vector;
+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.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Vector assembler is a transformer that combines a given list of columns into a single vector
+ * column. It will combine raw features and features generated by different feature transformers
+ * into a single feature vector. The input features of this transformer must be a vector feature or
+ * a numerical feature.
+ */
+public class VectorAssembler
+        implements Transformer<VectorAssembler>, VectorAssemblerParams<VectorAssembler> {
+    private final Map<Param<?>, Object> paramMap = new HashMap<>();
+    private static final double RATIO = 1.5;
+
+    public VectorAssembler() {
+        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(), TypeInformation.of(Vector.class)),
+                        ArrayUtils.addAll(inputTypeInfo.getFieldNames(), getOutputCol()));
+        DataStream<Row> output =
+                tEnv.toDataStream(inputs[0])
+                        .map(new AssemblerFunc(getInputCols(), getHandleInvalid()), outputTypeInfo);
+        Table outputTable = tEnv.fromDataStream(output);
+        return new Table[] {outputTable};
+    }
+
+    private static class AssemblerFunc implements MapFunction<Row, Row> {
+        private final String[] inputCols;
+        private final String handleInvalid;
+
+        public AssemblerFunc(String[] inputCols, String handleInvalid) {
+            this.inputCols = inputCols;
+            this.handleInvalid = handleInvalid;
+        }
+
+        @Override
+        public Row map(Row value) {
+            Object[] objects = new Object[inputCols.length];
+            for (int i = 0; i < objects.length; ++i) {
+                objects[i] = value.getField(inputCols[i]);
+            }
+            return Row.join(value, Row.of(assemble(objects, handleInvalid)));
+        }
+    }
+
+    @Override
+    public void save(String path) throws IOException {
+        ReadWriteUtils.saveMetadata(this, path);
+    }
+
+    public static VectorAssembler load(StreamTableEnvironment env, String path) throws IOException {
+        return ReadWriteUtils.loadStageParam(path);
+    }
+
+    @Override
+    public Map<Param<?>, Object> getParamMap() {
+        return paramMap;
+    }
+
+    private static Vector assemble(Object[] objects, String handleInvalid) {
+        int offset = 0;
+        Map<Integer, Double> map = new LinkedHashMap<>(objects.length);
+        for (Object object : objects) {
+            try {
+                Preconditions.checkNotNull(object, "VectorAssembler Error: input data is null.");

Review comment:
       `VectorAssembler Error` seems redundant given that the stacktrace should also contain `VectorAssember`.
   
   How about changing the error to `input column value should not be null`?
   

##########
File path: flink-ml-lib/src/main/java/org/apache/flink/ml/feature/vectorassembler/VectorAssembler.java
##########
@@ -0,0 +1,179 @@
+/*
+ * 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.vectorassembler;
+
+import org.apache.flink.api.common.functions.MapFunction;
+import org.apache.flink.api.common.typeinfo.TypeInformation;
+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.common.param.HasHandleInvalid;
+import org.apache.flink.ml.linalg.DenseVector;
+import org.apache.flink.ml.linalg.SparseVector;
+import org.apache.flink.ml.linalg.Vector;
+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.LinkedHashMap;
+import java.util.Map;
+
+/**
+ * Vector assembler is a transformer that combines a given list of columns into a single vector
+ * column. It will combine raw features and features generated by different feature transformers
+ * into a single feature vector. The input features of this transformer must be a vector feature or
+ * a numerical feature.
+ */
+public class VectorAssembler
+        implements Transformer<VectorAssembler>, VectorAssemblerParams<VectorAssembler> {
+    private final Map<Param<?>, Object> paramMap = new HashMap<>();
+    private static final double RATIO = 1.5;
+
+    public VectorAssembler() {
+        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(), TypeInformation.of(Vector.class)),
+                        ArrayUtils.addAll(inputTypeInfo.getFieldNames(), getOutputCol()));
+        DataStream<Row> output =
+                tEnv.toDataStream(inputs[0])
+                        .map(new AssemblerFunc(getInputCols(), getHandleInvalid()), outputTypeInfo);
+        Table outputTable = tEnv.fromDataStream(output);
+        return new Table[] {outputTable};
+    }
+
+    private static class AssemblerFunc implements MapFunction<Row, Row> {
+        private final String[] inputCols;
+        private final String handleInvalid;
+
+        public AssemblerFunc(String[] inputCols, String handleInvalid) {
+            this.inputCols = inputCols;
+            this.handleInvalid = handleInvalid;
+        }
+
+        @Override
+        public Row map(Row value) {
+            Object[] objects = new Object[inputCols.length];
+            for (int i = 0; i < objects.length; ++i) {
+                objects[i] = value.getField(inputCols[i]);
+            }
+            return Row.join(value, Row.of(assemble(objects, handleInvalid)));
+        }
+    }
+
+    @Override
+    public void save(String path) throws IOException {
+        ReadWriteUtils.saveMetadata(this, path);
+    }
+
+    public static VectorAssembler load(StreamTableEnvironment env, String path) throws IOException {
+        return ReadWriteUtils.loadStageParam(path);
+    }
+
+    @Override
+    public Map<Param<?>, Object> getParamMap() {
+        return paramMap;
+    }
+
+    private static Vector assemble(Object[] objects, String handleInvalid) {
+        int offset = 0;
+        Map<Integer, Double> map = new LinkedHashMap<>(objects.length);
+        for (Object object : objects) {
+            try {
+                Preconditions.checkNotNull(object, "VectorAssembler Error: input data is null.");
+                if (object instanceof Number) {
+                    map.put(offset++, ((Number) object).doubleValue());
+                } else if (object instanceof Vector) {
+                    offset = appendVector((Vector) object, map, offset);
+                } else {
+                    throw new UnsupportedOperationException(
+                            "Vector assembler : input type has not been supported yet.");
+                }
+            } catch (Exception e) {
+                switch (handleInvalid) {
+                    case HasHandleInvalid.ERROR_INVALID:
+                        throw new RuntimeException("Vector assembler failed.", e);
+                    case HasHandleInvalid.SKIP_INVALID:
+                        return null;
+                    default:
+                }
+            }
+        }
+
+        if (map.size() * RATIO > offset) {
+            DenseVector assembledVector = new DenseVector(offset);
+            for (int key : map.keySet()) {
+                assembledVector.values[key] = map.get(key);
+            }
+            return assembledVector;
+        } else {
+            return convertMapToSparseVector(offset, map);
+        }
+    }
+
+    private static int appendVector(Vector vec, Map<Integer, Double> map, int offset) {
+        if (vec instanceof SparseVector) {
+            SparseVector sparseVector = (SparseVector) vec;
+            int[] indices = sparseVector.indices;
+            double[] values = sparseVector.values;
+            for (int j = 0; j < indices.length; ++j) {

Review comment:
       nits: Could we use `for (int i = 0; i < indices.length; i++)` to be consistent with other for loop code style?




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