Preserve UDT element type for list(ip|binary) aggregates

Author: vinaykpud

core/src/main/java/org/opensearch/sql/executor/analytics/AnalyticsExecutionEngine.java

@@ -215,6 +215,8 @@ private List<ExprValue> convertRows(Iterable<Object[]> rows, List<RelDataTypeFie
    *       IpFieldMapper}'s {@code valueFetcher} output).
    *   <li>{@link BinaryType} + {@code byte[]} &rarr; base64-encoded string (matches the OpenSearch
    *       {@code binary} field wire format).
+   *   <li>{@code ARRAY<IpType>} / {@code ARRAY<BinaryType>} + {@code List<byte[]>} &rarr; element-wise
+   *       UDT-aware conversion for {@code list(ip|binary)} aggregates.
    *   <li>Anything else &rarr; existing {@link ExprValueUtils#fromObjectValue} path.
    * </ul>
    *
@@ -224,19 +226,55 @@ private List<ExprValue> convertRows(Iterable<Object[]> rows, List<RelDataTypeFie
   private static ExprValue toExprValue(Object value, RelDataType type) {
     if (value instanceof byte[] bytes) {
       if (type instanceof IpType) {
-        try {
-          return ExprValueUtils.stringValue(
-              InetAddresses.toAddrString(InetAddress.getByAddress(bytes)));
-        } catch (UnknownHostException e) {
-          throw new IllegalStateException("invalid IP buffer length: " + bytes.length, e);
-        }
+        return ipBytesToExprValue(bytes);
       } else if (type instanceof BinaryType) {
-        return ExprValueUtils.stringValue(Base64.getEncoder().encodeToString(bytes));
+        return binaryBytesToExprValue(bytes);
+      }
+    }
+    if (value instanceof List<?> list) {
+      RelDataType component = type.getComponentType();
+      if (component instanceof IpType) {
+        List<ExprValue> elems = new ArrayList<>(list.size());
+        for (Object elem : list) {
+          if (elem == null) {
+            elems.add(ExprValueUtils.nullValue());
+          } else if (elem instanceof byte[] eb) {
+            elems.add(ipBytesToExprValue(eb));
+          } else {
+            elems.add(ExprValueUtils.fromObjectValue(elem));
+          }
+        }
+        return new org.opensearch.sql.data.model.ExprCollectionValue(elems);
+      } else if (component instanceof BinaryType) {
+        List<ExprValue> elems = new ArrayList<>(list.size());
+        for (Object elem : list) {
+          if (elem == null) {
+            elems.add(ExprValueUtils.nullValue());
+          } else if (elem instanceof byte[] eb) {
+            elems.add(binaryBytesToExprValue(eb));
+          } else {
+            elems.add(ExprValueUtils.fromObjectValue(elem));
+          }
+        }
+        return new org.opensearch.sql.data.model.ExprCollectionValue(elems);
       }
     }
     return ExprValueUtils.fromObjectValue(value);
   }
 
+  private static ExprValue ipBytesToExprValue(byte[] bytes) {
+    try {
+      return ExprValueUtils.stringValue(
+          InetAddresses.toAddrString(InetAddress.getByAddress(bytes)));
+    } catch (UnknownHostException e) {
+      throw new IllegalStateException("invalid IP buffer length: " + bytes.length, e);
+    }
+  }
+
+  private static ExprValue binaryBytesToExprValue(byte[] bytes) {
+    return ExprValueUtils.stringValue(Base64.getEncoder().encodeToString(bytes));
+  }
+
   private Schema buildSchema(List<RelDataTypeField> fields) {
     List<Schema.Column> columns = new ArrayList<>();
     for (RelDataTypeField field : fields) {

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

@@ -499,9 +499,10 @@ public class PPLBuiltinOperators extends ReflectiveSqlOperatorTable {
           "pattern",
           ReturnTypes.explicit(UserDefinedFunctionUtils.nullablePatternAggList),
           null);
+  // ARG0_ARRAY preserves UDT element type so AnalyticsExecutionEngine can render IP/binary byte[].
   public static final SqlAggFunction LIST =
       createUserDefinedAggFunction(
-          ListAggFunction.class, "LIST", PPLReturnTypes.STRING_ARRAY, PPLOperandTypes.ANY_SCALAR);
+          ListAggFunction.class, "LIST", PPLReturnTypes.ARG0_ARRAY, PPLOperandTypes.ANY_SCALAR);
   public static final SqlAggFunction VALUES =
       createUserDefinedAggFunction(
           ValuesAggFunction.class,