enh: convert the month and year in interval-offset to a database precision duration

source/libs/parser/src/parTranslater.c

@@ -757,7 +757,8 @@ static bool isPrimaryKeyImpl(SNode* pExpr) {
     if (FUNCTION_TYPE_SELECT_VALUE == pFunc->funcType || FUNCTION_TYPE_GROUP_KEY == pFunc->funcType ||
         FUNCTION_TYPE_FIRST == pFunc->funcType || FUNCTION_TYPE_LAST == pFunc->funcType) {
       return isPrimaryKeyImpl(nodesListGetNode(pFunc->pParameterList, 0));
-    } else if (FUNCTION_TYPE_WSTART == pFunc->funcType || FUNCTION_TYPE_WEND == pFunc->funcType || FUNCTION_TYPE_IROWTS == pFunc->funcType) {
+    } else if (FUNCTION_TYPE_WSTART == pFunc->funcType || FUNCTION_TYPE_WEND == pFunc->funcType ||
+               FUNCTION_TYPE_IROWTS == pFunc->funcType) {
       return true;
     }
   }
@@ -3119,6 +3120,19 @@ static const char* getPrecisionStr(uint8_t precision) {
   return "unknown";
 }
 
+static void convertVarDuration(SValueNode* pOffset, uint8_t precision) {
+  const int64_t factors[3] = {NANOSECOND_PER_MSEC, NANOSECOND_PER_USEC, 1};
+  const int8_t  units[3] = {TIME_UNIT_MILLISECOND, TIME_UNIT_MICROSECOND, TIME_UNIT_NANOSECOND};
+
+  if (pOffset->unit == 'n') {
+    pOffset->datum.i = pOffset->datum.i * 31 * (NANOSECOND_PER_DAY / factors[precision]);
+  } else {
+    pOffset->datum.i = pOffset->datum.i * 365 * (NANOSECOND_PER_DAY / factors[precision]);
+  }
+
+  pOffset->unit = units[precision];
+}
+
 static int32_t checkIntervalWindow(STranslateContext* pCxt, SIntervalWindowNode* pInterval) {
   uint8_t precision = ((SColumnNode*)pInterval->pCol)->node.resType.precision;
 
@@ -3143,6 +3157,10 @@ static int32_t checkIntervalWindow(STranslateContext* pCxt, SIntervalWindowNode*
                        getMonthsFromTimeVal(pInter->datum.i, precision, pInter->unit))) {
       return generateSyntaxErrMsg(&pCxt->msgBuf, TSDB_CODE_PAR_INTER_OFFSET_TOO_BIG);
     }
+
+    if (pOffset->unit == 'n' || pOffset->unit == 'y') {
+      convertVarDuration(pOffset, precision);
+    }
   }
 
   if (NULL != pInterval->pSliding) {