Support spath command to extract all fields

core/src/main/java/org/opensearch/sql/ast/tree/SPath.java

@@ -28,7 +28,7 @@ public class SPath extends UnresolvedPlan {
 
   @Nullable private final String outField;
 
-  private final String path;
+  @Nullable private final String path;
 
   @Override
   public UnresolvedPlan attach(UnresolvedPlan child) {

core/src/main/java/org/opensearch/sql/calcite/CalciteRelNodeVisitor.java

@@ -688,7 +688,50 @@ public RelNode visitParse(Parse node, CalcitePlanContext context) {
 
   @Override
   public RelNode visitSpath(SPath node, CalcitePlanContext context) {
-    return visitEval(node.rewriteAsEval(), context);
+    if (node.getPath() != null) {
+      return visitEval(node.rewriteAsEval(), context);
+    } else {
+      return spathWithoutPath(node, context);
+    }
+  }
+
+  private RelNode spathWithoutPath(SPath node, CalcitePlanContext context) {
+    visitChildren(node, context);
+
+    // 1. Extract all fields from JSON in `inField` and merge with existing dynamic fields.
+    //  _MAP = MAP_APPEND(_MAP, JSON_EXTRACT_ALL(inField))
+    RexNode inField = QualifiedNameResolver.resolveFieldOrThrow(1, 0, node.getInField(), context);
+    RexNode map = context.rexBuilder.makeCall(BuiltinFunctionName.JSON_EXTRACT_ALL, inField);
+    if (context.fieldBuilder.isDynamicFieldsExist()) {
+      map =
+          context.rexBuilder.makeCall(
+              BuiltinFunctionName.MAP_APPEND, context.fieldBuilder.getDynamicFieldsMap(), map);
+    }
+
+    // 2. Merge dynamic fields with static fields.
+    //   static_field1 = APPEND(static_field1, _MAP[static_field1]), static_attr2 = ...
+    List<String> staticFieldNames = context.fieldBuilder.getStaticFieldNames();
+    List<RexNode> fields = new ArrayList<>();
+    for (String fieldName : staticFieldNames) {
+      RexNode field = context.fieldBuilder.staticField(fieldName);
+      RexNode appended =
+          context.rexBuilder.makeCall(
+              BuiltinFunctionName.INTERNAL_APPEND,
+              field,
+              context.rexBuilder.createItemAccess(map, fieldName));
+      fields.add(context.relBuilder.alias(appended, fieldName));
+    }
+
+    // 3. Dedupe dynamic fields with static fields.
+    //   _MAP = MAP_REMOVE(_MAP, [static_attr1, static_attr2, ...])
+    RexNode fieldNameArray = context.rexBuilder.createStringArrayLiteral(staticFieldNames);
+    RexNode dedupedMap =
+        context.rexBuilder.makeCall(BuiltinFunctionName.MAP_REMOVE, map, fieldNameArray);
+    fields.add(context.relBuilder.alias(dedupedMap, DynamicFieldsConstants.DYNAMIC_FIELDS_MAP));
+
+    context.relBuilder.project(fields);
+
+    return context.relBuilder.peek();
   }
 
   // might need to remove fields in _MAP

core/src/main/java/org/opensearch/sql/calcite/ExtendedRexBuilder.java

@@ -6,6 +6,7 @@
 package org.opensearch.sql.calcite;
 
 import com.google.common.collect.ImmutableList;
+import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.Locale;
@@ -25,7 +26,9 @@
 import org.opensearch.sql.data.type.ExprCoreType;
 import org.opensearch.sql.exception.ExpressionEvaluationException;
 import org.opensearch.sql.exception.SemanticCheckException;
+import org.opensearch.sql.expression.function.BuiltinFunctionName;
 import org.opensearch.sql.expression.function.PPLBuiltinOperators;
+import org.opensearch.sql.expression.function.PPLFuncImpTable;
 
 public class ExtendedRexBuilder extends RexBuilder {
 
@@ -170,4 +173,25 @@ public RexNode castToString(RexNode node) {
     RelDataType nullableStringType = getTypeFactory().createTypeWithNullability(stringType, true);
     return makeCast(nullableStringType, node, true, true);
   }
+
+  public RexNode createItemAccess(RexNode field, String itemName) {
+    return PPLFuncImpTable.INSTANCE.resolve(
+        this, BuiltinFunctionName.INTERNAL_ITEM, field, makeLiteral(itemName));
+  }
+
+  public RexNode makeCall(BuiltinFunctionName fn, RexNode... nodes) {
+    return PPLFuncImpTable.INSTANCE.resolve(this, fn, nodes);
+  }
+
+  public RexNode createStringArrayLiteral(List<String> values) {
+    RelDataType stringType = getTypeFactory().createSqlType(SqlTypeName.VARCHAR);
+    RelDataType arrayType = getTypeFactory().createArrayType(stringType, -1);
+
+    List<RexNode> elements = new ArrayList<>();
+    for (String value : values) {
+      elements.add(makeLiteral(value));
+    }
+
+    return makeCall(arrayType, SqlStdOperatorTable.ARRAY_VALUE_CONSTRUCTOR, elements);
+  }
 }

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

@@ -66,6 +66,7 @@ public enum BuiltinFunctionName {
   MAP_CONCAT(FunctionName.of("map_concat"), true),
   MAP_REMOVE(FunctionName.of("map_remove"), true),
   MVAPPEND(FunctionName.of("mvappend")),
+  INTERNAL_APPEND(FunctionName.of("append"), true),
   MVJOIN(FunctionName.of("mvjoin")),
   FORALL(FunctionName.of("forall")),
   EXISTS(FunctionName.of("exists")),

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

@@ -8,14 +8,32 @@
 import java.util.ArrayList;
 import java.util.List;
 
-/** Core logic for `mvappend` command to collect elements from list of args */
-public class MVAppendCore {
+/**
+ * Core logic for `mvappend` and internal `append` function to collect elements from list of args.
+ */
+public class AppendCore {
 
   /**
    * 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.
+   * of the list. See {@ref AppendFunctionImplTest} for detailed behavior.
+   */
+  public static Object collectElements(Object... args) {
+    List<Object> elements = collectElementsToList(args);
+
+    if (elements.isEmpty()) {
+      return null;
+    } else if (elements.size() == 1) {
+      // return the element in case of single element
+      return elements.get(0);
+    } else {
+      return elements;
+    }
+  }
+
+  /**
+   * Collect non-null elements from `args`. If an item is a list, it will collect non-null elements.
    */
-  public static List<Object> collectElements(Object... args) {
+  public static List<Object> collectElementsToList(Object... args) {
     List<Object> elements = new ArrayList<>();
 
     for (Object arg : args) {
@@ -28,7 +46,7 @@ public static List<Object> collectElements(Object... args) {
       }
     }
 
-    return elements.isEmpty() ? null : elements;
+    return elements;
   }
 
   private static void addListElements(List<?> list, List<Object> elements) {

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

@@ -0,0 +1,65 @@
+/*
+ * Copyright OpenSearch Contributors
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package org.opensearch.sql.expression.function.CollectionUDF;
+
+import java.util.List;
+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;
+
+/**
+ * Internal append function that appends all elements from arguments to create an array. Returns
+ * null if there is no element. Returns the scalar value if there is single element. Otherwise,
+ * returns a list containing all the elements from inputs.
+ */
+public class AppendFunctionImpl extends ImplementorUDF {
+
+  public AppendFunctionImpl() {
+    super(new AppendImplementor(), NullPolicy.ALL);
+  }
+
+  @Override
+  public SqlReturnTypeInference getReturnTypeInference() {
+    return sqlOperatorBinding -> {
+      RelDataTypeFactory typeFactory = sqlOperatorBinding.getTypeFactory();
+
+      if (sqlOperatorBinding.getOperandCount() == 0) {
+        return typeFactory.createSqlType(SqlTypeName.NULL);
+      }
+
+      // Return type is ANY as it could return scalar value (in case of single item) or array
+      return typeFactory.createSqlType(SqlTypeName.ANY);
+    };
+  }
+
+  @Override
+  public UDFOperandMetadata getOperandMetadata() {
+    return null;
+  }
+
+  public static class AppendImplementor implements NotNullImplementor {
+    @Override
+    public Expression implement(
+        RexToLixTranslator translator, RexCall call, List<Expression> translatedOperands) {
+      return Expressions.call(
+          Types.lookupMethod(AppendFunctionImpl.class, "append", Object[].class),
+          Expressions.newArrayInit(Object.class, translatedOperands));
+    }
+  }
+
+  public static Object append(Object... args) {
+    return AppendCore.collectElements(args);
+  }
+}

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

@@ -97,6 +97,15 @@ public Expression implement(
   }
 
   public static Object mvappend(Object... args) {
-    return MVAppendCore.collectElements(args);
+    return collectElements(args);
+  }
+
+  /**
+   * 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 = AppendCore.collectElementsToList(args);
+    return elements.isEmpty() ? null : elements;
   }
 }

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

@@ -24,8 +24,8 @@
 import org.opensearch.sql.expression.function.UDFOperandMetadata;
 
 /**
- * MapAppend function that merges two maps. All the values will be converted to list for type
- * consistency.
+ * MapAppend function that merges two maps. Value for the same key will be merged into an array by
+ * using {@ref: AppendCore}.
  */
 public class MapAppendFunctionImpl extends ImplementorUDF {
 
@@ -89,7 +89,7 @@ private static Map<String, Object> verifyMap(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)));
+      result.put(key, AppendCore.collectElements(map.get(key)));
     }
     return result;
   }
@@ -99,7 +99,7 @@ static Map<String, Object> mapAppendImpl(
     Map<String, Object> result = new HashMap<>();
 
     for (String key : mergeKeys(firstMap, secondMap)) {
-      result.put(key, MVAppendCore.collectElements(firstMap.get(key), secondMap.get(key)));
+      result.put(key, AppendCore.collectElements(firstMap.get(key), secondMap.get(key)));
     }
 
     return result;

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

@@ -42,6 +42,7 @@
 import org.opensearch.sql.calcite.utils.UserDefinedFunctionUtils;
 import org.opensearch.sql.data.type.ExprCoreType;
 import org.opensearch.sql.expression.datetime.DateTimeFunctions;
+import org.opensearch.sql.expression.function.CollectionUDF.AppendFunctionImpl;
 import org.opensearch.sql.expression.function.CollectionUDF.ArrayFunctionImpl;
 import org.opensearch.sql.expression.function.CollectionUDF.ExistsFunctionImpl;
 import org.opensearch.sql.expression.function.CollectionUDF.FilterFunctionImpl;
@@ -389,9 +390,10 @@ public class PPLBuiltinOperators extends ReflectiveSqlOperatorTable {
   public static final SqlOperator FORALL = new ForallFunctionImpl().toUDF("forall");
   public static final SqlOperator EXISTS = new ExistsFunctionImpl().toUDF("exists");
   public static final SqlOperator ARRAY = new ArrayFunctionImpl().toUDF("array");
-  public static final SqlOperator MAP_APPEND = new MapAppendFunctionImpl().toUDF("map_append");
+  public static final SqlOperator MAP_APPEND = new MapAppendFunctionImpl().toUDF("MAP_APPEND");
   public static final SqlOperator MAP_REMOVE = new MapRemoveFunctionImpl().toUDF("MAP_REMOVE");
-  public static final SqlOperator MVAPPEND = new MVAppendFunctionImpl().toUDF("mvappend");
+  public static final SqlOperator MVAPPEND = new MVAppendFunctionImpl().toUDF("MVAPPEND");
+  public static final SqlOperator INTERNAL_APPEND = new AppendFunctionImpl().toUDF("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

@@ -78,6 +78,7 @@
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.HOUR_OF_DAY;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.IF;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.IFNULL;
+import static org.opensearch.sql.expression.function.BuiltinFunctionName.INTERNAL_APPEND;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.INTERNAL_GROK;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.INTERNAL_ITEM;
 import static org.opensearch.sql.expression.function.BuiltinFunctionName.INTERNAL_PARSE;
@@ -957,6 +958,7 @@ void populate() {
 
       registerOperator(ARRAY, PPLBuiltinOperators.ARRAY);
       registerOperator(MVAPPEND, PPLBuiltinOperators.MVAPPEND);
+      registerOperator(INTERNAL_APPEND, PPLBuiltinOperators.INTERNAL_APPEND);
       registerOperator(MAP_APPEND, PPLBuiltinOperators.MAP_APPEND);
       registerOperator(MAP_CONCAT, SqlLibraryOperators.MAP_CONCAT);
       registerOperator(MAP_REMOVE, PPLBuiltinOperators.MAP_REMOVE);

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

@@ -0,0 +1,81 @@
+/*
+ * 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.assertNull;
+
+import java.util.Arrays;
+import java.util.List;
+import org.junit.jupiter.api.Test;
+
+public class AppendFunctionImplTest {
+
+  @Test
+  public void testAppendWithNoArguments() {
+    Object result = AppendFunctionImpl.append();
+    assertNull(result);
+  }
+
+  @Test
+  public void testAppendWithSingleElement() {
+    Object result = AppendFunctionImpl.append(42);
+    assertEquals(42, result);
+  }
+
+  @Test
+  public void testAppendWithMultipleElements() {
+    Object result = AppendFunctionImpl.append(1, 2, 3);
+    assertEquals(Arrays.asList(1, 2, 3), result);
+  }
+
+  @Test
+  public void testAppendWithNullValues() {
+    Object result = AppendFunctionImpl.append(null, 1, null);
+    assertEquals(1, result);
+  }
+
+  @Test
+  public void testAppendWithAllNulls() {
+    Object result = AppendFunctionImpl.append(null, null);
+    assertNull(result);
+  }
+
+  @Test
+  public void testAppendWithArrayFlattening() {
+    List<Integer> array1 = Arrays.asList(1, 2);
+    List<Integer> array2 = Arrays.asList(3, 4);
+    Object result = AppendFunctionImpl.append(array1, array2);
+    assertEquals(Arrays.asList(1, 2, 3, 4), result);
+  }
+
+  @Test
+  public void testAppendWithMixedTypes() {
+    List<Integer> array = Arrays.asList(1, 2);
+    Object result = AppendFunctionImpl.append(array, 3, "hello");
+    assertEquals(Arrays.asList(1, 2, 3, "hello"), result);
+  }
+
+  @Test
+  public void testAppendWithArrayAndNulls() {
+    List<Integer> array = Arrays.asList(1, 2);
+    Object result = AppendFunctionImpl.append(null, array, null, 3);
+    assertEquals(Arrays.asList(1, 2, 3), result);
+  }
+
+  @Test
+  public void testAppendWithSingleNull() {
+    Object result = AppendFunctionImpl.append((Object) null);
+    assertNull(result);
+  }
+
+  @Test
+  public void testAppendWithEmptyArray() {
+    List<Object> emptyArray = Arrays.asList();
+    Object result = AppendFunctionImpl.append(emptyArray, 1);
+    assertEquals(1, result);
+  }
+}