Tighten ADDDATE/SUBDATE return-type helper comments

Comment trims on top of d12407b (Marc Handalian's cherry-pick) — collapse
the multi-line Javadoc on isDateExprType/isTimeExprType to one-line case
names, and drop the inline narration at the two call sites
(PPLReturnTypes.TIME_APPLY_RETURN_TYPE,
AddSubDateFunction#getReturnTypeInference) that restated the helper
contract. Behavior unchanged.

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

Author: vinaykpud

core/src/main/java/org/opensearch/sql/calcite/utils/OpenSearchTypeFactory.java

@@ -279,20 +279,12 @@ public static ExprType convertRelDataTypeToExprType(RelDataType type) {
     return exprType;
   }
 
-  /**
-   * Whether {@code type} represents a DATE for the purpose of operand-conditional return-type
-   * inference (e.g. {@code ADDDATE(date, n)} returns DATE only when the base is a date). Recognizes
-   * both the SQL-plugin DATE UDT (via {@link #convertRelDataTypeToExprType}) and the
-   * analytics-route {@link DateOnlyType} column marker, which is {@code TIMESTAMP}-backed and would
-   * otherwise be misread as TIMESTAMP. Kept separate from {@link #convertRelDataTypeToExprType} so
-   * it isn't on the general planner path that round-trips through {@link
-   * #convertExprTypeToRelDataType}.
-   */
+  /** DATE check for return-type inference; recognizes the analytics-route {@link DateOnlyType}. */
   public static boolean isDateExprType(RelDataType type) {
     return type instanceof DateOnlyType || convertRelDataTypeToExprType(type) == ExprCoreType.DATE;
   }
 
-  /** TIME counterpart of {@link #isDateExprType} — recognizes the {@link TimeOnlyType} marker. */
+  /** TIME counterpart of {@link #isDateExprType}; recognizes {@link TimeOnlyType}. */
   public static boolean isTimeExprType(RelDataType type) {
     return type instanceof TimeOnlyType || convertRelDataTypeToExprType(type) == ExprCoreType.TIME;
   }

core/src/main/java/org/opensearch/sql/calcite/utils/PPLReturnTypes.java

@@ -35,8 +35,6 @@ private PPLReturnTypes() {}
   public static SqlReturnTypeInference TIME_APPLY_RETURN_TYPE =
       opBinding -> {
         RelDataType temporalType = opBinding.getOperandType(0);
-        // isTimeExprType so a TimeOnlyType column (analytics-route TIMESTAMP-backed time marker) is
-        // recognized as TIME; otherwise ADDTIME/SUBTIME on a time column lose the TIME return type.
         if (OpenSearchTypeFactory.isTimeExprType(temporalType)) {
           return UserDefinedFunctionUtils.NULLABLE_TIME_UDT;
         }

core/src/main/java/org/opensearch/sql/expression/function/udf/datetime/AddSubDateFunction.java

@@ -63,9 +63,6 @@ public SqlReturnTypeInference getReturnTypeInference() {
     return opBinding -> {
       RelDataType temporalType = opBinding.getOperandType(0);
       RelDataType temporalDeltaType = opBinding.getOperandType(1);
-      // isDateExprType (not convertRelDataTypeToExprType == DATE) so a DateOnlyType column — the
-      // analytics-route TIMESTAMP-backed date marker — is recognized as DATE; otherwise ADDDATE/
-      // SUBDATE on a date column would mis-declare TIMESTAMP and lose the DATE return type.
       if (OpenSearchTypeFactory.isDateExprType(temporalType)
           && SqlTypeFamily.NUMERIC.contains(temporalDeltaType)) {
         return NULLABLE_DATE_UDT;