Add ratio type information to metric structure

Signed-off-by: Wei-Chun, Chang <[email protected]>

piperider_cli/dbtutil.py

@@ -619,8 +619,9 @@ def _create_metric(name, filter=None, alias=None, derived_metric=None):
                 time_grains = derived_time_grains
 
             m = Metric(metric.get('name'),
-                       calculation_method='derived',
-                       expression=f"{numerator.get('name')} / {denominator.get('name')}",
+                       calculation_method='ratio',
+                       numerator=numerator.get('name'),
+                       denominator=denominator.get('name'),
                        time_grains=time_grains,
                        label=metric.get('label'), description=metric.get('description'), ref_metrics=ref_metrics,
                        ref_id=metric.get('unique_id'))

piperider_cli/metrics_engine/metrics.py

@@ -53,6 +53,8 @@ def __init__(
         calculation_method=None,
         time_grains=None,
         expression: str = None,
+        numerator: str = None,
+        denominator: str = None,
         label=None,
         description=None,
         ref_metrics=None,
@@ -63,6 +65,8 @@ def __init__(
         self.calculation_method = calculation_method
         self.time_grains = time_grains
         self.expression = expression
+        self.numerator = numerator
+        self.denominator = denominator
         self.label = label
         self.description = description
         self.ref_metrics: List[Metric] = ref_metrics or []
@@ -111,7 +115,7 @@ def _compose_query_name(grain: str, dimensions: List[str], label=False) -> str:
     def _get_query_stmt(self, metric: Metric, grain: str, dimension: List[str], date_spine_model: CTE):
         metric_column_name = metric.name
 
-        if metric.calculation_method == 'derived':
+        if metric.calculation_method == 'derived' or metric.calculation_method == 'ratio':
             selectable = None
 
             # Join all parent metrics
@@ -123,8 +127,11 @@ def _get_query_stmt(self, metric: Metric, grain: str, dimension: List[str], date
                 else:
                     selectable = join(selectable, cte, selectable.c.d == cte.c.d)
 
-            # a / b / c -> a / nullif(b, 0) / nullif(c, 0)
             expression = metric.expression
+            if metric.calculation_method == 'ratio':
+                expression = f"{metric.numerator}/{metric.denominator}"
+
+            # a / b / c -> a / nullif(b, 0) / nullif(c, 0)
             if '/' in expression:
                 expression_list = expression.split('/')
                 dividend = expression_list[0]