frac window agg to handle empty values mercifully

Author: Yomguithereal

src/moonblade/agg/window.rs

@@ -156,7 +156,10 @@ impl ConcreteWindowAggregation {
         match self {
             Self::Frac(expr, sum, _) => {
                 let value = eval_expression(expr, Some(index), record, headers_index)?;
-                sum.add(value.try_as_number().map_err(|err| err.specify("frac"))?);
+
+                if !value.is_nullish() {
+                    sum.add(value.try_as_number().map_err(|err| err.specify("frac"))?);
+                }
             }
             _ => (),
         };
@@ -258,7 +261,14 @@ impl ConcreteWindowAggregation {
                 Ok(DynamicValue::from(welford.add(float, *stat)))
             }
             Self::Frac(expr, sum, decimals) => {
+                // NOTE: we are evaluation the expression twice, because it seems less costly
+                // than allocating a cache for every record.
                 let value = eval_expression(expr, Some(index), record, headers_index)?;
+
+                if value.is_nullish() {
+                    return Ok(DynamicValue::None);
+                }
+
                 let number = value.try_as_number().map_err(|err| err.specify("frac"))?;
                 let frac = sum.get().map(|s| number / s);
 

tests/test_window.rs

@@ -398,6 +398,7 @@ fn window_frac() {
             svec!["1"],
             svec!["2"],
             svec!["3"],
+            svec![""],
             svec!["4"],
             svec!["5"],
         ],
@@ -411,6 +412,7 @@ fn window_frac() {
         svec!["1", "0.07"],
         svec!["2", "0.13"],
         svec!["3", "0.20"],
+        svec!["", ""],
         svec!["4", "0.27"],
         svec!["5", "0.33"],
     ];