Add MAP_APPEND internal function to Calcite PPL

core/src/main/java/org/opensearch/sql/expression/function/BuiltinFunctionName.java

@@ -63,6 +63,7 @@ public enum BuiltinFunctionName {
   ARRAY(FunctionName.of("array")),
   ARRAY_LENGTH(FunctionName.of("array_length")),
   MAP_CONCAT(FunctionName.of("map_concat"), true),
+  MAP_APPEND(FunctionName.of("map_append"), true),
   MVAPPEND(FunctionName.of("mvappend")),
   MVJOIN(FunctionName.of("mvjoin")),
   FORALL(FunctionName.of("forall")),

core/src/main/java/org/opensearch/sql/expression/function/CollectionUDF/MVAppendCore.java

@@ -0,0 +1,41 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.sql.expression.function.CollectionUDF;
+
+import java.util.ArrayList;
+import java.util.List;
+
+/** Core logic for `mvappend` command to collect elements from list of args */
+public class MVAppendCore {
+
+  /**
+   * Collect non-null elements from `args`. If an item is a list, it will collect non-null elements
+   * of the list. See {@ref MVAppendFunctionImplTest} for detailed behavior.
+   */
+  public static List<Object> collectElements(Object... args) {
+    List<Object> elements = new ArrayList<>();
+
+    for (Object arg : args) {
+      if (arg == null) {
+        continue;
+      } else if (arg instanceof List) {
+        addListElements((List<?>) arg, elements);
+      } else {
+        elements.add(arg);
+      }
+    }
+
+    return elements.isEmpty() ? null : elements;
+  }
+
+  private static void addListElements(List<?> list, List<Object> elements) {
+    for (Object item : list) {
+      if (item != null) {
+        elements.add(item);
+      }
+    }
+  }
+}

core/src/main/java/org/opensearch/sql/expression/function/CollectionUDF/MVAppendFunctionImpl.java

@@ -7,7 +7,6 @@
 
 import static org.apache.calcite.sql.type.SqlTypeUtil.createArrayType;
 
-import java.util.ArrayList;
 import java.util.List;
 import org.apache.calcite.adapter.enumerable.NotNullImplementor;
 import org.apache.calcite.adapter.enumerable.NullPolicy;
@@ -98,33 +97,6 @@ public Expression implement(
   }
 
   public static Object mvappend(Object... args) {
-    List<Object> elements = collectElements(args);
-    return elements.isEmpty() ? null : elements;
-  }
-
-  private static List<Object> collectElements(Object... args) {
-    List<Object> elements = new ArrayList<>();
-
-    for (Object arg : args) {
-      if (arg == null) {
-        continue;
-      }
-
-      if (arg instanceof List) {
-        addListElements((List<?>) arg, elements);
-      } else {
-        elements.add(arg);
-      }
-    }
-
-    return elements;
-  }
-
-  private static void addListElements(List<?> list, List<Object> elements) {
-    for (Object item : list) {
-      if (item != null) {
-        elements.add(item);
-      }
-    }
+    return MVAppendCore.collectElements(args);
   }
 }

core/src/main/java/org/opensearch/sql/expression/function/CollectionUDF/MapAppendFunctionImpl.java

@@ -0,0 +1,115 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.sql.expression.function.CollectionUDF;
+
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.List;
+import java.util.Map;
+import java.util.Set;
+import org.apache.calcite.adapter.enumerable.NotNullImplementor;
+import org.apache.calcite.adapter.enumerable.NullPolicy;
+import org.apache.calcite.adapter.enumerable.RexToLixTranslator;
+import org.apache.calcite.linq4j.tree.Expression;
+import org.apache.calcite.linq4j.tree.Expressions;
+import org.apache.calcite.linq4j.tree.Types;
+import org.apache.calcite.rel.type.RelDataTypeFactory;
+import org.apache.calcite.rex.RexCall;
+import org.apache.calcite.sql.type.SqlReturnTypeInference;
+import org.apache.calcite.sql.type.SqlTypeName;
+import org.opensearch.sql.expression.function.ImplementorUDF;
+import org.opensearch.sql.expression.function.UDFOperandMetadata;
+
+/**
+ * MapAppend function that merges two maps. All the values will be converted to list for type
+ * consistency.
+ */
+public class MapAppendFunctionImpl extends ImplementorUDF {
+
+  public MapAppendFunctionImpl() {
+    super(new MapAppendImplementor(), NullPolicy.ALL);
+  }
+
+  @Override
+  public SqlReturnTypeInference getReturnTypeInference() {
+    return sqlOperatorBinding -> {
+      RelDataTypeFactory typeFactory = sqlOperatorBinding.getTypeFactory();
+      return typeFactory.createMapType(
+          typeFactory.createSqlType(SqlTypeName.VARCHAR),
+          typeFactory.createSqlType(SqlTypeName.ANY));
+    };
+  }
+
+  @Override
+  public UDFOperandMetadata getOperandMetadata() {
+    return null;
+  }
+
+  public static class MapAppendImplementor implements NotNullImplementor {
+    @Override
+    public Expression implement(
+        RexToLixTranslator translator, RexCall call, List<Expression> translatedOperands) {
+      if (translatedOperands.size() != 2) {
+        throw new IllegalArgumentException("MAP_APPEND function requires exactly 2 arguments");
+      }
+
+      return Expressions.call(
+          Types.lookupMethod(MapAppendFunctionImpl.class, "mapAppend", Object.class, Object.class),
+          translatedOperands.get(0),
+          translatedOperands.get(1));
+    }
+  }
+
+  public static Object mapAppend(Object map1, Object map2) {
+    if (map1 == null && map2 == null) {
+      return null;
+    }
+    if (map1 == null) {
+      return mapAppendImpl(verifyMap(map2));
+    }
+    if (map2 == null) {
+      return mapAppendImpl(verifyMap(map1));
+    }
+
+    return mapAppendImpl(verifyMap(map1), verifyMap(map2));
+  }
+
+  @SuppressWarnings("unchecked")
+  private static Map<String, Object> verifyMap(Object map) {
+    if (!(map instanceof Map)) {
+      throw new IllegalArgumentException(
+          "MAP_APPEND function requires both arguments to be MAP type");
+    }
+    return (Map<String, Object>) map;
+  }
+
+  static Map<String, Object> mapAppendImpl(Map<String, Object> map) {
+    Map<String, Object> result = new HashMap<>();
+    for (String key : map.keySet()) {
+      result.put(key, MVAppendCore.collectElements(map.get(key)));
+    }
+    return result;
+  }
+
+  static Map<String, Object> mapAppendImpl(
+      Map<String, Object> firstMap, Map<String, Object> secondMap) {
+    Map<String, Object> result = new HashMap<>();
+
+    for (String key : mergeKeys(firstMap, secondMap)) {
+      result.put(key, MVAppendCore.collectElements(firstMap.get(key), secondMap.get(key)));
+    }
+
+    return result;
+  }
+
+  private static Set<String> mergeKeys(
+      Map<String, Object> firstMap, Map<String, Object> secondMap) {
+    Set<String> keys = new HashSet<>();
+    keys.addAll(firstMap.keySet());
+    keys.addAll(secondMap.keySet());
+    return keys;
+  }
+}

core/src/main/java/org/opensearch/sql/expression/function/PPLBuiltinOperators.java

@@ -47,6 +47,7 @@
 import org.opensearch.sql.expression.function.CollectionUDF.FilterFunctionImpl;
 import org.opensearch.sql.expression.function.CollectionUDF.ForallFunctionImpl;
 import org.opensearch.sql.expression.function.CollectionUDF.MVAppendFunctionImpl;
+import org.opensearch.sql.expression.function.CollectionUDF.MapAppendFunctionImpl;
 import org.opensearch.sql.expression.function.CollectionUDF.ReduceFunctionImpl;
 import org.opensearch.sql.expression.function.CollectionUDF.TransformFunctionImpl;
 import org.opensearch.sql.expression.function.jsonUDF.JsonAppendFunctionImpl;
@@ -388,6 +389,7 @@ public class PPLBuiltinOperators extends ReflectiveSqlOperatorTable {
   public static final SqlOperator EXISTS = new ExistsFunctionImpl().toUDF("exists");
   public static final SqlOperator ARRAY = new ArrayFunctionImpl().toUDF("array");
   public static final SqlOperator MVAPPEND = new MVAppendFunctionImpl().toUDF("mvappend");
+  public static final SqlOperator MAP_APPEND = new MapAppendFunctionImpl().toUDF("map_append");
   public static final SqlOperator FILTER = new FilterFunctionImpl().toUDF("filter");
   public static final SqlOperator TRANSFORM = new TransformFunctionImpl().toUDF("transform");
   public static final SqlOperator REDUCE = new ReduceFunctionImpl().toUDF("reduce");

core/src/main/java/org/opensearch/sql/expression/function/PPLFuncImpTable.java

@@ -124,6 +124,7 @@
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.LTRIM;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.MAKEDATE;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.MAKETIME;
+import static org.opensearch.sql.expression.function.BuiltinFunctionName.MAP_APPEND;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.MAP_CONCAT;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.MATCH;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.MATCH_BOOL_PREFIX;
@@ -897,6 +898,7 @@ void populate() {
 
       registerOperator(ARRAY, PPLBuiltinOperators.ARRAY);
       registerOperator(MVAPPEND, PPLBuiltinOperators.MVAPPEND);
+      registerOperator(MAP_APPEND, PPLBuiltinOperators.MAP_APPEND);
       registerOperator(ARRAY_LENGTH, SqlLibraryOperators.ARRAY_LENGTH);
       registerOperator(MAP_CONCAT, SqlLibraryOperators.MAP_CONCAT);
       registerOperator(FORALL, PPLBuiltinOperators.FORALL);

core/src/test/java/org/opensearch/sql/expression/function/CollectionUDF/MapAppendFunctionImplTest.java

@@ -0,0 +1,108 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.sql.expression.function.CollectionUDF;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+import org.junit.jupiter.api.Test;
+
+class MapAppendFunctionImplTest {
+  @Test
+  void testMapAppendWithNonOverlappingKeys() {
+    Map<String, Object> map1 = getMap1();
+    Map<String, Object> map2 = getMap2();
+
+    Map<String, Object> result = MapAppendFunctionImpl.mapAppendImpl(map1, map2);
+
+    assertEquals(4, result.size());
+    assertMapListValues(result, "a", "value1");
+    assertMapListValues(result, "b", "value2");
+    assertMapListValues(result, "c", "value3");
+    assertMapListValues(result, "d", "value4");
+  }
+
+  @Test
+  void testMapAppendWithOverlappingKeys() {
+    Map<String, Object> map1 = getMap1();
+    Map<String, Object> map2 = Map.of("b", "value3", "c", "value4");
+
+    Map<String, Object> result = MapAppendFunctionImpl.mapAppendImpl(map1, map2);
+
+    assertEquals(3, result.size());
+    assertMapListValues(result, "a", "value1");
+    assertMapListValues(result, "b", "value2", "value3");
+    assertMapListValues(result, "c", "value4");
+  }
+
+  @Test
+  void testMapAppendWithArrayValues() {
+    Map<String, Object> map1 = Map.of("a", List.of("item1", "item2"), "b", "single");
+    Map<String, Object> map2 = Map.of("a", "item3", "c", List.of("item4", "item5"));
+
+    Map<String, Object> result = MapAppendFunctionImpl.mapAppendImpl(map1, map2);
+
+    assertEquals(3, result.size());
+    assertMapListValues(result, "a", "item1", "item2", "item3");
+    assertMapListValues(result, "b", "single");
+    assertMapListValues(result, "c", "item4", "item5");
+  }
+
+  @Test
+  void testMapAppendWithNullValues() {
+    Map<String, Object> map1 = getMap1();
+    map1.put("b", null);
+    Map<String, Object> map2 = getMap2();
+    map2.put("b", "value2");
+    map2.put("a", null);
+
+    Map<String, Object> result = MapAppendFunctionImpl.mapAppendImpl(map1, map2);
+
+    assertEquals(4, result.size());
+    assertMapListValues(result, "a", "value1");
+    assertMapListValues(result, "b", "value2");
+    assertMapListValues(result, "c", "value3");
+    assertMapListValues(result, "d", "value4");
+  }
+
+  @Test
+  void testMapAppendWithSingleParam() {
+    Map<String, Object> map1 = getMap1();
+
+    Map<String, Object> result = MapAppendFunctionImpl.mapAppendImpl(map1);
+
+    assertEquals(2, result.size());
+    assertMapListValues(result, "a", "value1");
+    assertMapListValues(result, "b", "value2");
+  }
+
+  private Map<String, Object> getMap1() {
+    Map<String, Object> map1 = new HashMap<>();
+    map1.put("a", "value1");
+    map1.put("b", "value2");
+    return map1;
+  }
+
+  private Map<String, Object> getMap2() {
+    Map<String, Object> map2 = new HashMap<>();
+    map2.put("c", "value3");
+    map2.put("d", "value4");
+    return map2;
+  }
+
+  private void assertMapListValues(Map<String, Object> map, String key, Object... expectedValues) {
+    Object val = map.get(key);
+    assertTrue(val instanceof List);
+    List<Object> result = (List<Object>) val;
+    assertEquals(expectedValues.length, result.size());
+    for (int i = 0; i < expectedValues.length; i++) {
+      assertEquals(expectedValues[i], result.get(i));
+    }
+  }
+}