Jackie-Jiang commented on a change in pull request #6383:
URL: https://github.com/apache/incubator-pinot/pull/6383#discussion_r549454148



##########
File path: 
pinot-core/src/main/java/org/apache/pinot/core/operator/transform/function/LookupTransformFunction.java
##########
@@ -0,0 +1,290 @@
+/**
+ * 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.pinot.core.operator.transform.function;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.ArrayList;
+import com.google.common.base.Preconditions;
+import org.apache.commons.lang3.ArrayUtils;
+import org.apache.pinot.core.common.DataSource;
+import org.apache.pinot.core.data.manager.offline.DimensionTableDataManager;
+import org.apache.pinot.core.operator.blocks.ProjectionBlock;
+import org.apache.pinot.core.operator.transform.TransformResultMetadata;
+import org.apache.pinot.spi.data.FieldSpec;
+import org.apache.pinot.spi.data.readers.GenericRow;
+import org.apache.pinot.spi.data.readers.PrimaryKey;
+
+
+/**
+ * LOOKUP function takes 4 or more arguments:
+ * <ul>
+ *   <li><b>TableName:</b> name of the dimension table which will be used</li>
+ *   <li><b>ColumnName:</b> column name from the dimension table to look 
up</li>
+ *   <li><b>JoinKey:</b> primary key column name for the dimension table. 
Note: Only primary key[s] are supported for JoinKey</li>
+ *   <li><b>JoinValue:</b> primary key value</li>
+ *   ...<br>
+ *   *[If the dimension table has more then one primary keys (composite pk)]
+ *     <li><b>JoinKey2</b></li>
+ *     <li><b>JoinValue2</b></li>
+ *   ...
+ * </ul>
+ * <br>
+ * Example:
+ * <pre>{@code SELECT
+ *    baseballStats.playerName,
+ *    baseballStats.teamID,
+ *    LOOKUP('dimBaseballTeams', 'teamName', 'teamID', baseballStats.teamID)
+ * FROM
+ *    baseballStats
+ * LIMIT 10}</pre>
+ * <br>
+ * Above example joins the dimension table 'baseballTeams' into regular table 
'baseballStats' on 'teamID' key.
+ * Lookup function returns the value of the column 'teamName'.
+ */
+public class LookupTransformFunction extends BaseTransformFunction {
+  public static final String FUNCTION_NAME = "lookUp";
+  private static final String TABLE_NAME_SUFFIX = "_OFFLINE";
+
+  // Lookup parameters
+  private String _dimTableName;
+  private String _dimColumnName;
+  private final List<String> _joinKeys = new ArrayList<>();
+  private final List<FieldSpec> _joinValueFieldSpecs = new ArrayList<>();
+  private final List<TransformFunction> _joinValueFunctions = new 
ArrayList<>();
+
+  private DimensionTableDataManager _dataManager;
+  private FieldSpec _lookupColumnFieldSpec;
+
+  @Override
+  public String getName() {
+    return FUNCTION_NAME;
+  }
+
+  @Override
+  public void init(List<TransformFunction> arguments, Map<String, DataSource> 
dataSourceMap) {
+    // Check that there are correct number of arguments
+    Preconditions
+        .checkArgument(arguments.size() >= 4, "At least 4 arguments are 
required for LOOKUP transform function");

Review comment:
       List the expected arguments in the message

##########
File path: 
pinot-core/src/main/java/org/apache/pinot/core/operator/transform/function/LookupTransformFunction.java
##########
@@ -0,0 +1,290 @@
+/**
+ * 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.pinot.core.operator.transform.function;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.ArrayList;
+import com.google.common.base.Preconditions;
+import org.apache.commons.lang3.ArrayUtils;
+import org.apache.pinot.core.common.DataSource;
+import org.apache.pinot.core.data.manager.offline.DimensionTableDataManager;
+import org.apache.pinot.core.operator.blocks.ProjectionBlock;
+import org.apache.pinot.core.operator.transform.TransformResultMetadata;
+import org.apache.pinot.spi.data.FieldSpec;
+import org.apache.pinot.spi.data.readers.GenericRow;
+import org.apache.pinot.spi.data.readers.PrimaryKey;
+
+
+/**
+ * LOOKUP function takes 4 or more arguments:
+ * <ul>
+ *   <li><b>TableName:</b> name of the dimension table which will be used</li>
+ *   <li><b>ColumnName:</b> column name from the dimension table to look 
up</li>
+ *   <li><b>JoinKey:</b> primary key column name for the dimension table. 
Note: Only primary key[s] are supported for JoinKey</li>
+ *   <li><b>JoinValue:</b> primary key value</li>
+ *   ...<br>
+ *   *[If the dimension table has more then one primary keys (composite pk)]
+ *     <li><b>JoinKey2</b></li>
+ *     <li><b>JoinValue2</b></li>
+ *   ...
+ * </ul>
+ * <br>
+ * Example:
+ * <pre>{@code SELECT
+ *    baseballStats.playerName,
+ *    baseballStats.teamID,
+ *    LOOKUP('dimBaseballTeams', 'teamName', 'teamID', baseballStats.teamID)
+ * FROM
+ *    baseballStats
+ * LIMIT 10}</pre>
+ * <br>
+ * Above example joins the dimension table 'baseballTeams' into regular table 
'baseballStats' on 'teamID' key.
+ * Lookup function returns the value of the column 'teamName'.
+ */
+public class LookupTransformFunction extends BaseTransformFunction {
+  public static final String FUNCTION_NAME = "lookUp";
+  private static final String TABLE_NAME_SUFFIX = "_OFFLINE";

Review comment:
       Use `TableNameBuilder` instead

##########
File path: 
pinot-core/src/main/java/org/apache/pinot/core/operator/transform/function/LookupTransformFunction.java
##########
@@ -0,0 +1,290 @@
+/**
+ * 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.pinot.core.operator.transform.function;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.ArrayList;
+import com.google.common.base.Preconditions;
+import org.apache.commons.lang3.ArrayUtils;
+import org.apache.pinot.core.common.DataSource;
+import org.apache.pinot.core.data.manager.offline.DimensionTableDataManager;
+import org.apache.pinot.core.operator.blocks.ProjectionBlock;
+import org.apache.pinot.core.operator.transform.TransformResultMetadata;
+import org.apache.pinot.spi.data.FieldSpec;
+import org.apache.pinot.spi.data.readers.GenericRow;
+import org.apache.pinot.spi.data.readers.PrimaryKey;
+
+
+/**
+ * LOOKUP function takes 4 or more arguments:
+ * <ul>
+ *   <li><b>TableName:</b> name of the dimension table which will be used</li>
+ *   <li><b>ColumnName:</b> column name from the dimension table to look 
up</li>
+ *   <li><b>JoinKey:</b> primary key column name for the dimension table. 
Note: Only primary key[s] are supported for JoinKey</li>
+ *   <li><b>JoinValue:</b> primary key value</li>
+ *   ...<br>
+ *   *[If the dimension table has more then one primary keys (composite pk)]
+ *     <li><b>JoinKey2</b></li>
+ *     <li><b>JoinValue2</b></li>
+ *   ...
+ * </ul>
+ * <br>
+ * Example:
+ * <pre>{@code SELECT
+ *    baseballStats.playerName,
+ *    baseballStats.teamID,
+ *    LOOKUP('dimBaseballTeams', 'teamName', 'teamID', baseballStats.teamID)
+ * FROM
+ *    baseballStats
+ * LIMIT 10}</pre>
+ * <br>
+ * Above example joins the dimension table 'baseballTeams' into regular table 
'baseballStats' on 'teamID' key.
+ * Lookup function returns the value of the column 'teamName'.
+ */
+public class LookupTransformFunction extends BaseTransformFunction {
+  public static final String FUNCTION_NAME = "lookUp";
+  private static final String TABLE_NAME_SUFFIX = "_OFFLINE";
+
+  // Lookup parameters
+  private String _dimTableName;
+  private String _dimColumnName;
+  private final List<String> _joinKeys = new ArrayList<>();
+  private final List<FieldSpec> _joinValueFieldSpecs = new ArrayList<>();
+  private final List<TransformFunction> _joinValueFunctions = new 
ArrayList<>();
+
+  private DimensionTableDataManager _dataManager;
+  private FieldSpec _lookupColumnFieldSpec;
+
+  @Override
+  public String getName() {
+    return FUNCTION_NAME;
+  }
+
+  @Override
+  public void init(List<TransformFunction> arguments, Map<String, DataSource> 
dataSourceMap) {
+    // Check that there are correct number of arguments
+    Preconditions
+        .checkArgument(arguments.size() >= 4, "At least 4 arguments are 
required for LOOKUP transform function");
+    Preconditions
+        .checkArgument(arguments.size() % 2 == 0, "Should have the same number 
of JoinKey and JoinValue arguments");
+
+    TransformFunction dimTableNameFunction = arguments.get(0);
+    Preconditions.checkArgument(dimTableNameFunction instanceof 
LiteralTransformFunction,
+        "First argument must be a literal(string) representing the dimension 
table name");
+    _dimTableName = ((LiteralTransformFunction) 
dimTableNameFunction).getLiteral();
+
+    TransformFunction dimColumnFunction = arguments.get(1);
+    Preconditions.checkArgument(dimColumnFunction instanceof 
LiteralTransformFunction,
+        "Second argument must be a literal(string) representing the column 
name from dimension table to lookup");
+    _dimColumnName = ((LiteralTransformFunction) 
dimColumnFunction).getLiteral();
+
+    List<TransformFunction> joinArguments = arguments.subList(2, 
arguments.size());
+    for (int i = 0; i < joinArguments.size() / 2; i++) {

Review comment:
       (nit) extract `joinArguments.size()` as a local variable

##########
File path: 
pinot-core/src/main/java/org/apache/pinot/core/operator/transform/function/LookupTransformFunction.java
##########
@@ -0,0 +1,290 @@
+/**
+ * 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.pinot.core.operator.transform.function;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.ArrayList;
+import com.google.common.base.Preconditions;
+import org.apache.commons.lang3.ArrayUtils;
+import org.apache.pinot.core.common.DataSource;
+import org.apache.pinot.core.data.manager.offline.DimensionTableDataManager;
+import org.apache.pinot.core.operator.blocks.ProjectionBlock;
+import org.apache.pinot.core.operator.transform.TransformResultMetadata;
+import org.apache.pinot.spi.data.FieldSpec;
+import org.apache.pinot.spi.data.readers.GenericRow;
+import org.apache.pinot.spi.data.readers.PrimaryKey;
+
+
+/**
+ * LOOKUP function takes 4 or more arguments:
+ * <ul>
+ *   <li><b>TableName:</b> name of the dimension table which will be used</li>
+ *   <li><b>ColumnName:</b> column name from the dimension table to look 
up</li>
+ *   <li><b>JoinKey:</b> primary key column name for the dimension table. 
Note: Only primary key[s] are supported for JoinKey</li>
+ *   <li><b>JoinValue:</b> primary key value</li>
+ *   ...<br>
+ *   *[If the dimension table has more then one primary keys (composite pk)]
+ *     <li><b>JoinKey2</b></li>
+ *     <li><b>JoinValue2</b></li>
+ *   ...
+ * </ul>
+ * <br>
+ * Example:
+ * <pre>{@code SELECT
+ *    baseballStats.playerName,
+ *    baseballStats.teamID,
+ *    LOOKUP('dimBaseballTeams', 'teamName', 'teamID', baseballStats.teamID)
+ * FROM
+ *    baseballStats
+ * LIMIT 10}</pre>
+ * <br>
+ * Above example joins the dimension table 'baseballTeams' into regular table 
'baseballStats' on 'teamID' key.
+ * Lookup function returns the value of the column 'teamName'.
+ */
+public class LookupTransformFunction extends BaseTransformFunction {
+  public static final String FUNCTION_NAME = "lookUp";
+  private static final String TABLE_NAME_SUFFIX = "_OFFLINE";
+
+  // Lookup parameters
+  private String _dimTableName;
+  private String _dimColumnName;
+  private final List<String> _joinKeys = new ArrayList<>();
+  private final List<FieldSpec> _joinValueFieldSpecs = new ArrayList<>();
+  private final List<TransformFunction> _joinValueFunctions = new 
ArrayList<>();
+
+  private DimensionTableDataManager _dataManager;
+  private FieldSpec _lookupColumnFieldSpec;
+
+  @Override
+  public String getName() {
+    return FUNCTION_NAME;
+  }
+
+  @Override
+  public void init(List<TransformFunction> arguments, Map<String, DataSource> 
dataSourceMap) {
+    // Check that there are correct number of arguments
+    Preconditions
+        .checkArgument(arguments.size() >= 4, "At least 4 arguments are 
required for LOOKUP transform function");
+    Preconditions
+        .checkArgument(arguments.size() % 2 == 0, "Should have the same number 
of JoinKey and JoinValue arguments");
+
+    TransformFunction dimTableNameFunction = arguments.get(0);
+    Preconditions.checkArgument(dimTableNameFunction instanceof 
LiteralTransformFunction,
+        "First argument must be a literal(string) representing the dimension 
table name");
+    _dimTableName = ((LiteralTransformFunction) 
dimTableNameFunction).getLiteral();
+
+    TransformFunction dimColumnFunction = arguments.get(1);
+    Preconditions.checkArgument(dimColumnFunction instanceof 
LiteralTransformFunction,
+        "Second argument must be a literal(string) representing the column 
name from dimension table to lookup");
+    _dimColumnName = ((LiteralTransformFunction) 
dimColumnFunction).getLiteral();
+
+    List<TransformFunction> joinArguments = arguments.subList(2, 
arguments.size());
+    for (int i = 0; i < joinArguments.size() / 2; i++) {
+      TransformFunction dimJoinKeyFunction = joinArguments.get((i * 2));
+      Preconditions.checkArgument(dimJoinKeyFunction instanceof 
LiteralTransformFunction,
+          "JoinKey argument must be a literal(string) representing the primary 
key for the dimension table");
+      _joinKeys.add(((LiteralTransformFunction) 
dimJoinKeyFunction).getLiteral());
+
+      TransformFunction factJoinValueFunction = joinArguments.get((i * 2) + 1);
+      TransformResultMetadata factJoinValueFunctionResultMetadata = 
factJoinValueFunction.getResultMetadata();
+      
Preconditions.checkArgument(factJoinValueFunctionResultMetadata.isSingleValue(),
+          "JoinValue argument must be a single value expression");
+      _joinValueFunctions.add(factJoinValueFunction);
+    }
+
+    // Validate lookup table and relevant columns
+    _dataManager = 
DimensionTableDataManager.getInstanceByTableName(_dimTableName + 
TABLE_NAME_SUFFIX);
+    Preconditions
+        .checkArgument(_dataManager != null, String.format("Dimension table 
does not exist: %s", _dimTableName));
+
+    _lookupColumnFieldSpec = _dataManager.getColumnFieldSpec(_dimColumnName);
+    Preconditions.checkArgument(_lookupColumnFieldSpec != null,
+        String.format("Column does not exist in dimension table: %s:%s", 
_dimTableName, _dimColumnName));
+
+    for (String joinKey : _joinKeys) {
+      FieldSpec pkColumnSpec = _dataManager.getColumnFieldSpec(joinKey);
+      Preconditions.checkArgument(pkColumnSpec != null,
+          String.format("Primary key column doesn't exist in dimension table: 
%s:%s", _dimTableName, joinKey));
+      _joinValueFieldSpecs.add(pkColumnSpec);
+    }
+  }
+
+  @Override
+  public TransformResultMetadata getResultMetadata() {
+    return new TransformResultMetadata(_lookupColumnFieldSpec.getDataType(),
+        _lookupColumnFieldSpec.isSingleValueField(), false);
+  }
+
+  private Object[] lookup(ProjectionBlock projectionBlock) {
+    int numPkColumns = _joinKeys.size();
+    int numDocuments = projectionBlock.getNumDocs();
+    Object[][] pkColumns = new Object[numPkColumns][];
+    for (int i = 0; i < numPkColumns; i++) {
+      FieldSpec.DataType colType = _joinValueFieldSpecs.get(i).getDataType();
+      TransformFunction tf = _joinValueFunctions.get(i);
+      switch (colType) {
+        case STRING:
+          pkColumns[i] = tf.transformToStringValuesSV(projectionBlock);
+          break;
+        case INT:
+          pkColumns[i] = 
ArrayUtils.toObject(tf.transformToIntValuesSV(projectionBlock));
+          break;
+        case LONG:
+          pkColumns[i] = 
ArrayUtils.toObject(tf.transformToLongValuesSV(projectionBlock));
+          break;
+        default:
+          throw new IllegalStateException("Unknown column type for primary 
key");
+      }
+    }
+
+    Object[] resultSet = new Object[numDocuments];
+    for (int i = 0; i < numDocuments; i++) {
+      // prepare pk
+      Object[] pkValues = new Object[numPkColumns];
+      for (int j = 0; j < numPkColumns; j++) {
+        pkValues[j] = pkColumns[j][i];
+      }
+      // lookup
+      GenericRow row = _dataManager.lookupRowByPrimaryKey(new 
PrimaryKey(pkValues));
+      if (row != null && row.getFieldToValueMap().containsKey(_dimColumnName)) 
{
+        resultSet[i] = row.getValue(_dimColumnName);
+      }
+    }
+    return resultSet;
+  }
+
+  @Override
+  public int[] transformToIntValuesSV(ProjectionBlock projectionBlock) {
+    Object[] lookupObjects = lookup(projectionBlock);
+    int[] resultSet = new int[lookupObjects.length];
+    Arrays.fill(resultSet, ((Number) 
_lookupColumnFieldSpec.getDefaultNullValue()).intValue());
+    for (int i = 0; i < lookupObjects.length; i++) {
+      resultSet[i] = ((Number) lookupObjects[i]).intValue();

Review comment:
       Need to check `null`, same for other places

##########
File path: 
pinot-core/src/main/java/org/apache/pinot/core/operator/transform/function/LookupTransformFunction.java
##########
@@ -0,0 +1,290 @@
+/**
+ * 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.pinot.core.operator.transform.function;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.ArrayList;
+import com.google.common.base.Preconditions;
+import org.apache.commons.lang3.ArrayUtils;
+import org.apache.pinot.core.common.DataSource;
+import org.apache.pinot.core.data.manager.offline.DimensionTableDataManager;
+import org.apache.pinot.core.operator.blocks.ProjectionBlock;
+import org.apache.pinot.core.operator.transform.TransformResultMetadata;
+import org.apache.pinot.spi.data.FieldSpec;
+import org.apache.pinot.spi.data.readers.GenericRow;
+import org.apache.pinot.spi.data.readers.PrimaryKey;
+
+
+/**
+ * LOOKUP function takes 4 or more arguments:
+ * <ul>
+ *   <li><b>TableName:</b> name of the dimension table which will be used</li>
+ *   <li><b>ColumnName:</b> column name from the dimension table to look 
up</li>
+ *   <li><b>JoinKey:</b> primary key column name for the dimension table. 
Note: Only primary key[s] are supported for JoinKey</li>
+ *   <li><b>JoinValue:</b> primary key value</li>
+ *   ...<br>
+ *   *[If the dimension table has more then one primary keys (composite pk)]
+ *     <li><b>JoinKey2</b></li>
+ *     <li><b>JoinValue2</b></li>
+ *   ...
+ * </ul>
+ * <br>
+ * Example:
+ * <pre>{@code SELECT
+ *    baseballStats.playerName,
+ *    baseballStats.teamID,
+ *    LOOKUP('dimBaseballTeams', 'teamName', 'teamID', baseballStats.teamID)
+ * FROM
+ *    baseballStats
+ * LIMIT 10}</pre>
+ * <br>
+ * Above example joins the dimension table 'baseballTeams' into regular table 
'baseballStats' on 'teamID' key.
+ * Lookup function returns the value of the column 'teamName'.
+ */
+public class LookupTransformFunction extends BaseTransformFunction {
+  public static final String FUNCTION_NAME = "lookUp";
+  private static final String TABLE_NAME_SUFFIX = "_OFFLINE";
+
+  // Lookup parameters
+  private String _dimTableName;
+  private String _dimColumnName;
+  private final List<String> _joinKeys = new ArrayList<>();
+  private final List<FieldSpec> _joinValueFieldSpecs = new ArrayList<>();
+  private final List<TransformFunction> _joinValueFunctions = new 
ArrayList<>();
+
+  private DimensionTableDataManager _dataManager;
+  private FieldSpec _lookupColumnFieldSpec;
+
+  @Override
+  public String getName() {
+    return FUNCTION_NAME;
+  }
+
+  @Override
+  public void init(List<TransformFunction> arguments, Map<String, DataSource> 
dataSourceMap) {
+    // Check that there are correct number of arguments
+    Preconditions
+        .checkArgument(arguments.size() >= 4, "At least 4 arguments are 
required for LOOKUP transform function");
+    Preconditions
+        .checkArgument(arguments.size() % 2 == 0, "Should have the same number 
of JoinKey and JoinValue arguments");
+
+    TransformFunction dimTableNameFunction = arguments.get(0);
+    Preconditions.checkArgument(dimTableNameFunction instanceof 
LiteralTransformFunction,
+        "First argument must be a literal(string) representing the dimension 
table name");
+    _dimTableName = ((LiteralTransformFunction) 
dimTableNameFunction).getLiteral();
+
+    TransformFunction dimColumnFunction = arguments.get(1);
+    Preconditions.checkArgument(dimColumnFunction instanceof 
LiteralTransformFunction,
+        "Second argument must be a literal(string) representing the column 
name from dimension table to lookup");
+    _dimColumnName = ((LiteralTransformFunction) 
dimColumnFunction).getLiteral();
+
+    List<TransformFunction> joinArguments = arguments.subList(2, 
arguments.size());
+    for (int i = 0; i < joinArguments.size() / 2; i++) {
+      TransformFunction dimJoinKeyFunction = joinArguments.get((i * 2));
+      Preconditions.checkArgument(dimJoinKeyFunction instanceof 
LiteralTransformFunction,
+          "JoinKey argument must be a literal(string) representing the primary 
key for the dimension table");
+      _joinKeys.add(((LiteralTransformFunction) 
dimJoinKeyFunction).getLiteral());
+
+      TransformFunction factJoinValueFunction = joinArguments.get((i * 2) + 1);
+      TransformResultMetadata factJoinValueFunctionResultMetadata = 
factJoinValueFunction.getResultMetadata();
+      
Preconditions.checkArgument(factJoinValueFunctionResultMetadata.isSingleValue(),
+          "JoinValue argument must be a single value expression");
+      _joinValueFunctions.add(factJoinValueFunction);
+    }
+
+    // Validate lookup table and relevant columns
+    _dataManager = 
DimensionTableDataManager.getInstanceByTableName(_dimTableName + 
TABLE_NAME_SUFFIX);
+    Preconditions
+        .checkArgument(_dataManager != null, String.format("Dimension table 
does not exist: %s", _dimTableName));
+
+    _lookupColumnFieldSpec = _dataManager.getColumnFieldSpec(_dimColumnName);
+    Preconditions.checkArgument(_lookupColumnFieldSpec != null,
+        String.format("Column does not exist in dimension table: %s:%s", 
_dimTableName, _dimColumnName));
+
+    for (String joinKey : _joinKeys) {
+      FieldSpec pkColumnSpec = _dataManager.getColumnFieldSpec(joinKey);
+      Preconditions.checkArgument(pkColumnSpec != null,
+          String.format("Primary key column doesn't exist in dimension table: 
%s:%s", _dimTableName, joinKey));
+      _joinValueFieldSpecs.add(pkColumnSpec);
+    }
+  }
+
+  @Override
+  public TransformResultMetadata getResultMetadata() {
+    return new TransformResultMetadata(_lookupColumnFieldSpec.getDataType(),
+        _lookupColumnFieldSpec.isSingleValueField(), false);
+  }
+
+  private Object[] lookup(ProjectionBlock projectionBlock) {
+    int numPkColumns = _joinKeys.size();
+    int numDocuments = projectionBlock.getNumDocs();
+    Object[][] pkColumns = new Object[numPkColumns][];
+    for (int i = 0; i < numPkColumns; i++) {
+      FieldSpec.DataType colType = _joinValueFieldSpecs.get(i).getDataType();
+      TransformFunction tf = _joinValueFunctions.get(i);
+      switch (colType) {

Review comment:
       Please support all data types (usually we order them as followings: INT, 
LONG, FLOAT, DOUBLE, STRING, BYTES)

##########
File path: 
pinot-core/src/main/java/org/apache/pinot/core/operator/transform/function/LookupTransformFunction.java
##########
@@ -0,0 +1,290 @@
+/**
+ * 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.pinot.core.operator.transform.function;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.ArrayList;
+import com.google.common.base.Preconditions;
+import org.apache.commons.lang3.ArrayUtils;
+import org.apache.pinot.core.common.DataSource;
+import org.apache.pinot.core.data.manager.offline.DimensionTableDataManager;
+import org.apache.pinot.core.operator.blocks.ProjectionBlock;
+import org.apache.pinot.core.operator.transform.TransformResultMetadata;
+import org.apache.pinot.spi.data.FieldSpec;
+import org.apache.pinot.spi.data.readers.GenericRow;
+import org.apache.pinot.spi.data.readers.PrimaryKey;
+
+
+/**
+ * LOOKUP function takes 4 or more arguments:
+ * <ul>
+ *   <li><b>TableName:</b> name of the dimension table which will be used</li>
+ *   <li><b>ColumnName:</b> column name from the dimension table to look 
up</li>
+ *   <li><b>JoinKey:</b> primary key column name for the dimension table. 
Note: Only primary key[s] are supported for JoinKey</li>
+ *   <li><b>JoinValue:</b> primary key value</li>
+ *   ...<br>
+ *   *[If the dimension table has more then one primary keys (composite pk)]
+ *     <li><b>JoinKey2</b></li>
+ *     <li><b>JoinValue2</b></li>
+ *   ...
+ * </ul>
+ * <br>
+ * Example:
+ * <pre>{@code SELECT
+ *    baseballStats.playerName,
+ *    baseballStats.teamID,
+ *    LOOKUP('dimBaseballTeams', 'teamName', 'teamID', baseballStats.teamID)
+ * FROM
+ *    baseballStats
+ * LIMIT 10}</pre>
+ * <br>
+ * Above example joins the dimension table 'baseballTeams' into regular table 
'baseballStats' on 'teamID' key.
+ * Lookup function returns the value of the column 'teamName'.
+ */
+public class LookupTransformFunction extends BaseTransformFunction {
+  public static final String FUNCTION_NAME = "lookUp";
+  private static final String TABLE_NAME_SUFFIX = "_OFFLINE";
+
+  // Lookup parameters
+  private String _dimTableName;
+  private String _dimColumnName;
+  private final List<String> _joinKeys = new ArrayList<>();
+  private final List<FieldSpec> _joinValueFieldSpecs = new ArrayList<>();
+  private final List<TransformFunction> _joinValueFunctions = new 
ArrayList<>();
+
+  private DimensionTableDataManager _dataManager;
+  private FieldSpec _lookupColumnFieldSpec;
+
+  @Override
+  public String getName() {
+    return FUNCTION_NAME;
+  }
+
+  @Override
+  public void init(List<TransformFunction> arguments, Map<String, DataSource> 
dataSourceMap) {
+    // Check that there are correct number of arguments
+    Preconditions
+        .checkArgument(arguments.size() >= 4, "At least 4 arguments are 
required for LOOKUP transform function");
+    Preconditions
+        .checkArgument(arguments.size() % 2 == 0, "Should have the same number 
of JoinKey and JoinValue arguments");
+
+    TransformFunction dimTableNameFunction = arguments.get(0);
+    Preconditions.checkArgument(dimTableNameFunction instanceof 
LiteralTransformFunction,
+        "First argument must be a literal(string) representing the dimension 
table name");
+    _dimTableName = ((LiteralTransformFunction) 
dimTableNameFunction).getLiteral();

Review comment:
       Handle table name with suffix
   ```suggestion
       _dimTableName = 
TableNameBuilder.OFFLINE.tableNameWithType(((LiteralTransformFunction) 
dimTableNameFunction).getLiteral());
   ```

##########
File path: 
pinot-core/src/main/java/org/apache/pinot/core/operator/transform/function/LookupTransformFunction.java
##########
@@ -0,0 +1,290 @@
+/**
+ * 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.pinot.core.operator.transform.function;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Map;
+import java.util.ArrayList;
+import com.google.common.base.Preconditions;
+import org.apache.commons.lang3.ArrayUtils;
+import org.apache.pinot.core.common.DataSource;
+import org.apache.pinot.core.data.manager.offline.DimensionTableDataManager;
+import org.apache.pinot.core.operator.blocks.ProjectionBlock;
+import org.apache.pinot.core.operator.transform.TransformResultMetadata;
+import org.apache.pinot.spi.data.FieldSpec;
+import org.apache.pinot.spi.data.readers.GenericRow;
+import org.apache.pinot.spi.data.readers.PrimaryKey;
+
+
+/**
+ * LOOKUP function takes 4 or more arguments:
+ * <ul>
+ *   <li><b>TableName:</b> name of the dimension table which will be used</li>
+ *   <li><b>ColumnName:</b> column name from the dimension table to look 
up</li>
+ *   <li><b>JoinKey:</b> primary key column name for the dimension table. 
Note: Only primary key[s] are supported for JoinKey</li>
+ *   <li><b>JoinValue:</b> primary key value</li>
+ *   ...<br>
+ *   *[If the dimension table has more then one primary keys (composite pk)]
+ *     <li><b>JoinKey2</b></li>
+ *     <li><b>JoinValue2</b></li>
+ *   ...
+ * </ul>
+ * <br>
+ * Example:
+ * <pre>{@code SELECT
+ *    baseballStats.playerName,
+ *    baseballStats.teamID,
+ *    LOOKUP('dimBaseballTeams', 'teamName', 'teamID', baseballStats.teamID)
+ * FROM
+ *    baseballStats
+ * LIMIT 10}</pre>
+ * <br>
+ * Above example joins the dimension table 'baseballTeams' into regular table 
'baseballStats' on 'teamID' key.
+ * Lookup function returns the value of the column 'teamName'.
+ */
+public class LookupTransformFunction extends BaseTransformFunction {
+  public static final String FUNCTION_NAME = "lookUp";
+  private static final String TABLE_NAME_SUFFIX = "_OFFLINE";
+
+  // Lookup parameters
+  private String _dimTableName;
+  private String _dimColumnName;
+  private final List<String> _joinKeys = new ArrayList<>();
+  private final List<FieldSpec> _joinValueFieldSpecs = new ArrayList<>();
+  private final List<TransformFunction> _joinValueFunctions = new 
ArrayList<>();
+
+  private DimensionTableDataManager _dataManager;
+  private FieldSpec _lookupColumnFieldSpec;
+
+  @Override
+  public String getName() {
+    return FUNCTION_NAME;
+  }
+
+  @Override
+  public void init(List<TransformFunction> arguments, Map<String, DataSource> 
dataSourceMap) {
+    // Check that there are correct number of arguments
+    Preconditions
+        .checkArgument(arguments.size() >= 4, "At least 4 arguments are 
required for LOOKUP transform function");
+    Preconditions
+        .checkArgument(arguments.size() % 2 == 0, "Should have the same number 
of JoinKey and JoinValue arguments");
+
+    TransformFunction dimTableNameFunction = arguments.get(0);
+    Preconditions.checkArgument(dimTableNameFunction instanceof 
LiteralTransformFunction,
+        "First argument must be a literal(string) representing the dimension 
table name");
+    _dimTableName = ((LiteralTransformFunction) 
dimTableNameFunction).getLiteral();
+
+    TransformFunction dimColumnFunction = arguments.get(1);
+    Preconditions.checkArgument(dimColumnFunction instanceof 
LiteralTransformFunction,
+        "Second argument must be a literal(string) representing the column 
name from dimension table to lookup");
+    _dimColumnName = ((LiteralTransformFunction) 
dimColumnFunction).getLiteral();
+
+    List<TransformFunction> joinArguments = arguments.subList(2, 
arguments.size());
+    for (int i = 0; i < joinArguments.size() / 2; i++) {
+      TransformFunction dimJoinKeyFunction = joinArguments.get((i * 2));
+      Preconditions.checkArgument(dimJoinKeyFunction instanceof 
LiteralTransformFunction,
+          "JoinKey argument must be a literal(string) representing the primary 
key for the dimension table");
+      _joinKeys.add(((LiteralTransformFunction) 
dimJoinKeyFunction).getLiteral());
+
+      TransformFunction factJoinValueFunction = joinArguments.get((i * 2) + 1);
+      TransformResultMetadata factJoinValueFunctionResultMetadata = 
factJoinValueFunction.getResultMetadata();
+      
Preconditions.checkArgument(factJoinValueFunctionResultMetadata.isSingleValue(),
+          "JoinValue argument must be a single value expression");
+      _joinValueFunctions.add(factJoinValueFunction);
+    }
+
+    // Validate lookup table and relevant columns
+    _dataManager = 
DimensionTableDataManager.getInstanceByTableName(_dimTableName + 
TABLE_NAME_SUFFIX);
+    Preconditions
+        .checkArgument(_dataManager != null, String.format("Dimension table 
does not exist: %s", _dimTableName));
+
+    _lookupColumnFieldSpec = _dataManager.getColumnFieldSpec(_dimColumnName);
+    Preconditions.checkArgument(_lookupColumnFieldSpec != null,
+        String.format("Column does not exist in dimension table: %s:%s", 
_dimTableName, _dimColumnName));
+
+    for (String joinKey : _joinKeys) {
+      FieldSpec pkColumnSpec = _dataManager.getColumnFieldSpec(joinKey);
+      Preconditions.checkArgument(pkColumnSpec != null,
+          String.format("Primary key column doesn't exist in dimension table: 
%s:%s", _dimTableName, joinKey));
+      _joinValueFieldSpecs.add(pkColumnSpec);
+    }
+  }
+
+  @Override
+  public TransformResultMetadata getResultMetadata() {
+    return new TransformResultMetadata(_lookupColumnFieldSpec.getDataType(),
+        _lookupColumnFieldSpec.isSingleValueField(), false);
+  }
+
+  private Object[] lookup(ProjectionBlock projectionBlock) {
+    int numPkColumns = _joinKeys.size();
+    int numDocuments = projectionBlock.getNumDocs();
+    Object[][] pkColumns = new Object[numPkColumns][];
+    for (int i = 0; i < numPkColumns; i++) {
+      FieldSpec.DataType colType = _joinValueFieldSpecs.get(i).getDataType();
+      TransformFunction tf = _joinValueFunctions.get(i);
+      switch (colType) {
+        case STRING:
+          pkColumns[i] = tf.transformToStringValuesSV(projectionBlock);
+          break;
+        case INT:
+          pkColumns[i] = 
ArrayUtils.toObject(tf.transformToIntValuesSV(projectionBlock));
+          break;
+        case LONG:
+          pkColumns[i] = 
ArrayUtils.toObject(tf.transformToLongValuesSV(projectionBlock));
+          break;
+        default:
+          throw new IllegalStateException("Unknown column type for primary 
key");
+      }
+    }
+
+    Object[] resultSet = new Object[numDocuments];
+    for (int i = 0; i < numDocuments; i++) {
+      // prepare pk
+      Object[] pkValues = new Object[numPkColumns];
+      for (int j = 0; j < numPkColumns; j++) {
+        pkValues[j] = pkColumns[j][i];
+      }
+      // lookup
+      GenericRow row = _dataManager.lookupRowByPrimaryKey(new 
PrimaryKey(pkValues));
+      if (row != null && row.getFieldToValueMap().containsKey(_dimColumnName)) 
{
+        resultSet[i] = row.getValue(_dimColumnName);
+      }

Review comment:
       We can save one map lookup
   ```suggestion
         if (row != null) {
           resultSet[i] = row.getValue(_dimColumnName);
         }
   ```




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