Add type mapping for UNDEFINED

Signed-off-by: Tomoyuki Morita <moritato@amazon.com>

Author: ykmr1224

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

@@ -184,6 +184,18 @@ public void testSpathAndStats() throws IOException {
     verifyDataRows(result, rows(1L, null), rows(1L, "Jane"), rows(1L, "John"));
   }
 
+  @Test
+  public void testSpathAndEventStats() throws IOException {
+    JSONObject result =
+        executeQuery(
+            source(
+                TEST_INDEX_DYNAMIC_FIELDS,
+                "spath input=json_data | eventstats avg(age) as avg | fields id, name, avg"));
+
+    verifySchema(result, schema("id", "bigint"), schema("name", "string"), schema("avg", "double"));
+    verifyDataRows(result, rows(1, "John", 27.5), rows(2, "Jane", 27.5), rows(3, null, 27.5));
+  }
+
   @Test
   public void testSpathDynamicFieldsExplain() throws IOException {
     executeQuery(

opensearch/src/main/java/org/opensearch/sql/opensearch/data/value/OpenSearchExprValueFactory.java

@@ -17,6 +17,7 @@
 import static org.opensearch.sql.data.type.ExprCoreType.STRUCT;
 import static org.opensearch.sql.data.type.ExprCoreType.TIME;
 import static org.opensearch.sql.data.type.ExprCoreType.TIMESTAMP;
+import static org.opensearch.sql.data.type.ExprCoreType.UNDEFINED;
 import static org.opensearch.sql.utils.DateTimeFormatters.STRICT_HOUR_MINUTE_SECOND_FORMATTER;
 import static org.opensearch.sql.utils.DateTimeFormatters.STRICT_YEAR_MONTH_DAY_FORMATTER;
 
@@ -133,6 +134,7 @@ public void extendTypeMapping(Map<String, OpenSearchDataType> typeMapping) {
           .put(
               OpenSearchDataType.of(OpenSearchDataType.MappingType.Binary),
               (c, dt) -> new OpenSearchExprBinaryValue(c.stringValue()))
+          .put(OpenSearchDataType.of(UNDEFINED), (c, dt) -> parseContent(c))
           .build();
 
   /** Constructor of OpenSearchExprValueFactory. */
@@ -213,7 +215,7 @@ private ExprValue parse(
     }
   }
 
-  private ExprValue parseContent(Content content) {
+  private static ExprValue parseContent(Content content) {
     if (content.isNumber()) {
       if (content.isInt()) {
         return new ExprIntegerValue(content.intValue());

opensearch/src/test/java/org/opensearch/sql/opensearch/data/value/OpenSearchExprValueFactoryTest.java

@@ -58,6 +58,7 @@
 import org.opensearch.sql.data.model.ExprTupleValue;
 import org.opensearch.sql.data.model.ExprValue;
 import org.opensearch.sql.data.model.ExprValueUtils;
+import org.opensearch.sql.data.type.ExprCoreType;
 import org.opensearch.sql.opensearch.data.type.OpenSearchDataType;
 import org.opensearch.sql.opensearch.data.type.OpenSearchDateType;
 import org.opensearch.sql.opensearch.data.type.OpenSearchTextType;
@@ -122,6 +123,7 @@ class OpenSearchExprValueFactoryTest {
           .put(fieldIp, OpenSearchDataType.of(OpenSearchDataType.MappingType.Ip))
           .put("geoV", OpenSearchDataType.of(OpenSearchDataType.MappingType.GeoPoint))
           .put("binaryV", OpenSearchDataType.of(OpenSearchDataType.MappingType.Binary))
+          .put("undefinedV", OpenSearchDataType.of(ExprCoreType.UNDEFINED))
           .build();
   private static final double TOLERANCE = 1E-5;
   private final OpenSearchExprValueFactory exprValueFactory =
@@ -948,6 +950,17 @@ public void constructFromInvalidJsonThrowException() {
     assertEquals("invalid json: {\"invalid_json:1}.", exception.getMessage());
   }
 
+  @Test
+  public void constructUndefined() {
+    assertAll(
+        () ->
+            assertEquals(
+                stringValue("text"), tupleValue("{\"undefinedV\":\"text\"}").get("undefinedV")),
+        () -> assertEquals(stringValue("text"), constructFromObject("undefinedV", "text")),
+        () -> assertEquals(integerValue(1), tupleValue("{\"undefinedV\":1}").get("undefinedV")),
+        () -> assertEquals(integerValue(1), constructFromObject("undefinedV", 1)));
+  }
+
   @Test
   public void noTypeFoundForMapping() {
     assertEquals(nullValue(), tupleValue("{\"not_exist\":[]}").get("not_exist"));