Fix UDFOperandMetadata type checking for variable-arity UDFs in SQL path

Calcite's FamilyOperandTypeChecker.checkOperandTypes requires exact
operand count match against the family list size, which fails for SQL
calls with fewer optional args. Both wrap() overloads now derive
List<RelDataType> from SqlCallBinding and delegate to PPL's existing
type checkers (PPLFamilyTypeCheckerWrapper, PPLCompositeTypeChecker)
which correctly handle optional parameters by checking count range
first, then validating only the provided operands.

Signed-off-by: Chen Dai <daichen@amazon.com>

Author: dai-chen

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

@@ -5,6 +5,7 @@
 
 package org.opensearch.sql.expression.function;
 
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
 import org.apache.calcite.rel.type.RelDataType;
@@ -48,7 +49,19 @@ public List<String> paramNames() {
 
       @Override
       public boolean checkOperandTypes(SqlCallBinding callBinding, boolean throwOnFailure) {
-        return typeChecker.checkOperandTypesWithoutTypeCoercion(callBinding, throwOnFailure);
+        // Derive operand types and validate via PPLFamilyTypeCheckerWrapper which correctly
+        // handles optional parameters. Calcite's FamilyOperandTypeChecker.checkOperandTypes
+        // requires exact count match against the family list size, rejecting valid calls with
+        // fewer optional args.
+        List<RelDataType> argTypes = deriveOperandTypes(callBinding, callBinding.getOperandCount());
+        if (new PPLTypeChecker.PPLFamilyTypeCheckerWrapper(typeChecker)
+            .checkOperandTypes(argTypes)) {
+          return true;
+        }
+        if (throwOnFailure) {
+          throw callBinding.newValidationSignatureError();
+        }
+        return false;
       }
 
       @Override
@@ -91,7 +104,18 @@ public List<String> paramNames() {
 
       @Override
       public boolean checkOperandTypes(SqlCallBinding callBinding, boolean throwOnFailure) {
-        return typeChecker.checkOperandTypes(callBinding, throwOnFailure);
+        // Derive operand types and validate via PPLCompositeTypeChecker which correctly handles
+        // variable-arity functions with optional parameters. Calcite's built-in
+        // FamilyOperandTypeChecker.checkOperandTypes requires exact operand count match against
+        // the family list size, rejecting valid calls with fewer optional args.
+        List<RelDataType> argTypes = deriveOperandTypes(callBinding, callBinding.getOperandCount());
+        if (new PPLTypeChecker.PPLCompositeTypeChecker(typeChecker).checkOperandTypes(argTypes)) {
+          return true;
+        }
+        if (throwOnFailure) {
+          throw callBinding.newValidationSignatureError();
+        }
+        return false;
       }
 
       @Override
@@ -106,6 +130,16 @@ public String getAllowedSignatures(SqlOperator op, String opName) {
     };
   }
 
+  /** Derives operand types from a SqlCallBinding for use with PPL type checkers. */
+  private static List<RelDataType> deriveOperandTypes(SqlCallBinding callBinding, int count) {
+    List<RelDataType> types = new ArrayList<>(count);
+    for (int i = 0; i < count; i++) {
+      types.add(
+          callBinding.getValidator().deriveType(callBinding.getScope(), callBinding.operand(i)));
+    }
+    return types;
+  }
+
   static UDFOperandMetadata wrapUDT(List<List<ExprType>> allowSignatures) {
     return new UDTOperandMetadata(allowSignatures);
   }