Preserve raw element type in ListAggFunction

V3 LIST accumulator was stringifying every element via String.valueOf,
which conflicted with the ARG0_ARRAY return-type declaration on
PPLBuiltinOperators.LIST and threw ClassCastException at runtime
(e.g. (Boolean) "true"). Drop the String.valueOf and accumulate raw
Object values; update CalciteMultiValueStatsIT numeric/boolean
assertions to match the unquoted JSON output.

Signed-off-by: Vinay Krishna Pudyodu <vinkrish.neo@gmail.com>

Author: vinaykpud

core/src/main/java/org/opensearch/sql/calcite/udf/udaf/ListAggFunction.java

@@ -40,25 +40,24 @@ public Object result(ListAccumulator accumulator) {
 
   @Override
   public ListAccumulator add(ListAccumulator acc, Object... values) {
-    // Handle case where no values are passed
     if (values == null || values.length == 0) {
       return acc;
     }
 
     Object value = values[0];
 
-    // Filter out null values and enforce 100-item limit
+    // Preserve raw element type so the result matches the ARG0_ARRAY return-type
+    // declaration on PPLBuiltinOperators.LIST. Stringifying here would break Calcite's
+    // type-checking and the response-boundary UDT dispatch for ip / binary columns.
     if (value != null && acc.size() < DEFAULT_LIMIT) {
-      // Convert value to string, handling all types safely
-      String stringValue = String.valueOf(value);
-      acc.add(stringValue);
+      acc.add(value);
     }
 
     return acc;
   }
 
   public static class ListAccumulator implements Accumulator {
-    private final List<String> values;
+    private final List<Object> values;
 
     public ListAccumulator() {
       this.values = new ArrayList<>();
@@ -69,7 +68,7 @@ public Object value(Object... argList) {
       return values;
     }
 
-    public void add(String value) {
+    public void add(Object value) {
       values.add(value);
     }
 

integ-test/src/test/java/org/opensearch/sql/calcite/remote/CalciteMultiValueStatsIT.java

@@ -43,7 +43,7 @@ public void testListFunctionWithBoolean() throws IOException {
                 "source=%s | stats list(boolean_value) as bool_list",
                 TEST_INDEX_DATATYPE_NONNUMERIC));
     verifySchema(response, schema("bool_list", "array"));
-    verifyDataRows(response, rows(List.of("true")));
+    verifyDataRows(response, rows(List.of(true)));
   }
 
   @Test
@@ -53,7 +53,7 @@ public void testListFunctionWithByte() throws IOException {
             String.format(
                 "source=%s | stats list(byte_number) as byte_list", TEST_INDEX_DATATYPE_NUMERIC));
     verifySchema(response, schema("byte_list", "array"));
-    verifyDataRows(response, rows(List.of("4")));
+    verifyDataRows(response, rows(List.of(4)));
   }
 
   @Test
@@ -63,7 +63,7 @@ public void testListFunctionWithShort() throws IOException {
             String.format(
                 "source=%s | stats list(short_number) as short_list", TEST_INDEX_DATATYPE_NUMERIC));
     verifySchema(response, schema("short_list", "array"));
-    verifyDataRows(response, rows(List.of("3")));
+    verifyDataRows(response, rows(List.of(3)));
   }
 
   @Test
@@ -73,7 +73,7 @@ public void testListFunctionWithInteger() throws IOException {
             String.format(
                 "source=%s | stats list(integer_number) as int_list", TEST_INDEX_DATATYPE_NUMERIC));
     verifySchema(response, schema("int_list", "array"));
-    verifyDataRows(response, rows(List.of("2")));
+    verifyDataRows(response, rows(List.of(2)));
   }
 
   @Test
@@ -83,7 +83,7 @@ public void testListFunctionWithLong() throws IOException {
             String.format(
                 "source=%s | stats list(long_number) as long_list", TEST_INDEX_DATATYPE_NUMERIC));
     verifySchema(response, schema("long_list", "array"));
-    verifyDataRows(response, rows(List.of("1")));
+    verifyDataRows(response, rows(List.of(1)));
   }
 
   @Test
@@ -93,7 +93,7 @@ public void testListFunctionWithFloat() throws IOException {
             String.format(
                 "source=%s | stats list(float_number) as float_list", TEST_INDEX_DATATYPE_NUMERIC));
     verifySchema(response, schema("float_list", "array"));
-    verifyDataRows(response, rows(List.of("6.2")));
+    verifyDataRows(response, rows(List.of(6.2)));
   }
 
   @Test
@@ -104,7 +104,7 @@ public void testListFunctionWithDouble() throws IOException {
                 "source=%s | stats list(double_number) as double_list",
                 TEST_INDEX_DATATYPE_NUMERIC));
     verifySchema(response, schema("double_list", "array"));
-    verifyDataRows(response, rows(List.of("5.1")));
+    verifyDataRows(response, rows(List.of(5.1)));
   }
 
   @Test
@@ -188,7 +188,7 @@ public void testListFunctionWithNullValues() throws IOException {
             String.format("source=%s | head 5 | stats list(int0) as int_list", TEST_INDEX_CALCS));
     verifySchema(response, schema("int_list", "array"));
     // Nulls are filtered out by list function
-    verifyDataRows(response, rows(List.of("1", "7")));
+    verifyDataRows(response, rows(List.of(1, 7)));
   }
 
   @Test
@@ -217,7 +217,7 @@ public void testListFunctionMultipleFields() throws IOException {
     assert response.has("datarows");
     // Values should be collected from the first 3 rows (str2 and int2 columns)
     // The actual values depend on the test data - int2 column contains 5, -4, 5
-    verifyDataRows(response, rows(List.of("one", "two", "three"), List.of("5", "-4", "5")));
+    verifyDataRows(response, rows(List.of("one", "two", "three"), List.of(5, -4, 5)));
   }
 
   @Test
@@ -275,7 +275,7 @@ public void testListFunctionWithArithmeticExpression() throws IOException {
             String.format(
                 "source=%s | head 3 | stats list(int3 + 1) as arithmetic_list", TEST_INDEX_CALCS));
     verifySchema(response, schema("arithmetic_list", "array"));
-    verifyDataRows(response, rows(List.of("9", "14", "3")));
+    verifyDataRows(response, rows(List.of(9, 14, 3)));
   }
 
   // ==================== VALUES Function Tests ====================