[feat] Add a new count aggregation for querying past results

docs/manpage.rst

@@ -1544,6 +1544,7 @@ The following aggregation functions are supported:
 - ``sum``: return the sum of every group
 - ``median``: return the median of every group
 - ``p<QQ>``: return the QQ% percentile of every group. Two digits a required even for quantiles less than 10%, e.g., the 5% percentile should be requested as ``p05``.
+- ``count``: return the number of elements of every group
 
 There is also the pseudo-function ``stats``, which is essentially a shortcut for ``min,p01,p05,median,p95,p99,max,mean,std``.
 It can also be applied to any other attribute than ``pval``
@@ -1664,7 +1665,7 @@ Note that parts that have a grammar defined elsewhere (e.g., Python attributes a
    <aggr_spec> ::= <aggr_any> | <aggr_pval>
    <aggr_any> ::= <aggr_fn> "(" <attr> ")"
    <aggr_pval> ::= <aggr_fn>
-   <aggr_fn> ::= "first" | "last" | "max" | "min" | "mean" | "median" | "std" | "sum" | <quantile>
+   <aggr_fn> ::= "first" | "last" | "max" | "min" | "mean" | "median" | "std" | "sum" | <quantile> | "count"
    <quantile> ::= "p" [0-9] [0-9]
    <cols> ::= <extra_cols> | <explicit_cols>
    <extra_cols> ::= ("+" <attr>)+

reframe/frontend/reporting/utility.py

@@ -17,7 +17,7 @@ class Aggregation:
 
     AGG_REGEX = re.compile(r'(?P<op>\S+)\((?P<col>\S+)\)|(?P<op2>\S+)')
     OP_REGEX = re.compile(
-        r'min|max|median|mean|std|first|last|sum|stats|p\d{2}'
+        r'min|max|median|mean|std|first|last|sum|stats|count|p\d{2}'
     )
     Q_REGEX = re.compile(r'p(\d{2})')
 
@@ -89,6 +89,8 @@ def _expr_from_op(col, op):
                 return pl.col(col).last().alias(f'{col} (last)')
             elif op == 'sum':
                 return pl.col(col).sum().alias(f'{col} (sum)')
+            elif op == 'count':
+                return pl.col(col).count().alias(f'{col} (count)')
             elif m := self.Q_REGEX.match(op):
                 perc = m.group(1)
                 if perc == '00':

unittests/test_reporting.py

@@ -228,7 +228,8 @@ def test_parse_cmp_spec_period(time_period):
 
 @pytest.fixture(params=['first', 'last', 'mean', 'median',
                         'min', 'max', 'std', 'stats', 'sum',
-                        'p00', 'p01', 'p05', 'p95', 'p99'])
+                        'p00', 'p01', 'p05', 'p95', 'p99',
+                        'count'])
 def aggregator(request):
     return request.param
 
@@ -289,6 +290,9 @@ def test_parse_cmp_spec_aggregations(aggregator):
         assert agg['pval (p95)'][0] == 10
     elif aggregator == 'p05':
         assert agg['pval (p99)'][0] == 10
+    elif aggregator == 'count':
+        assert 'pval (count)' in agg.columns
+        assert agg['pval (count)'][0] == num_recs
 
     # Check variant without base period
     match = parse_cmp_spec(f'now-1d:now/{aggregator}:/')