Utilize coercion

Signed-off-by: Tomoyuki Morita <[email protected]>

Author: ykmr1224

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

@@ -182,6 +182,13 @@ public static boolean hasString(List<RexNode> rexNodeList) {
         .anyMatch(t -> t == ExprCoreType.STRING);
   }
 
+  public static boolean hasAny(List<RexNode> rexNodeList) {
+    return rexNodeList.stream()
+        .map(RexNode::getType)
+        .map(OpenSearchTypeFactory::convertRelDataTypeToExprType)
+        .anyMatch(t -> t == ExprCoreType.UNDEFINED);
+  }
+
   private static final Set<ExprType> NUMBER_TYPES = ExprCoreType.numberTypes();
 
   private static final List<CoercionRule> COMMON_COERCION_RULES =

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

@@ -468,7 +468,7 @@ static List<RexNode> validateFunctionArgs(
       List<RexNode> fields = new ArrayList<>();
       fields.add(field);
       fields.addAll(argList);
-      if (CoercionUtils.hasString(fields)) {
+      if (CoercionUtils.hasString(fields) || CoercionUtils.hasAny(fields)) {
         coercionNodes = CoercionUtils.castArguments(rexBuilder, signature.typeChecker(), fields);
       }
       if (coercionNodes == null) {

integ-test/src/test/java/org/opensearch/sql/calcite/standalone/CalciteDynamicFieldsAggregationIT.java

@@ -93,8 +93,7 @@ public void testStatsByDynamicField() throws IOException {
   public void testStatsWithDynamicField() throws IOException {
     String query =
         source(
-            TEST_INDEX_DYNAMIC,
-            "stats avg(cast(salary as int)) as avg by department | fields department, avg");
+            TEST_INDEX_DYNAMIC, "stats avg(salary) as avg by department | fields department, avg");
 
     assertExplainYaml(
         query,
@@ -168,8 +167,7 @@ public void testEventstatsWithDynamicField() throws IOException {
     String query =
         source(
             TEST_INDEX_DYNAMIC,
-            "eventstats avg(cast(salary as int)) as"
-                + " avg by department | fields id, city, department, avg");
+            "eventstats avg(salary) as avg by department " + "| fields id, city, department, avg");
 
     assertExplainYaml(
         query,