Add group() aggregator (#7480)

* Add group() aggregator

Signed-off-by: Julien Pivotto <roidelapluie@inuits.eu>

docs/querying/operators.md

@@ -187,6 +187,7 @@ vector of fewer elements with aggregated values:
 * `min` (select minimum over dimensions)
 * `max` (select maximum over dimensions)
 * `avg` (calculate the average over dimensions)
+* `group` (all values in the resulting vector are 1)
 * `stddev` (calculate population standard deviation over dimensions)
 * `stdvar` (calculate population standard variance over dimensions)
 * `count` (count number of elements in the vector)

promql/engine.go

@@ -1978,20 +1978,23 @@ func (ev *evaluator) aggregation(op parser.ItemType, grouping []string, without
 			if k > inputVecLen {
 				resultSize = inputVecLen
 			}
-			if op == parser.STDVAR || op == parser.STDDEV {
-				result[groupingKey].value = 0.0
-			} else if op == parser.TOPK || op == parser.QUANTILE {
+			switch op {
+			case parser.STDVAR, parser.STDDEV:
+				result[groupingKey].value = 0
+			case parser.TOPK, parser.QUANTILE:
 				result[groupingKey].heap = make(vectorByValueHeap, 0, resultSize)
 				heap.Push(&result[groupingKey].heap, &Sample{
 					Point:  Point{V: s.V},
 					Metric: s.Metric,
 				})
-			} else if op == parser.BOTTOMK {
+			case parser.BOTTOMK:
 				result[groupingKey].reverseHeap = make(vectorByReverseValueHeap, 0, resultSize)
 				heap.Push(&result[groupingKey].reverseHeap, &Sample{
 					Point:  Point{V: s.V},
 					Metric: s.Metric,
 				})
+			case parser.GROUP:
+				result[groupingKey].value = 1
 			}
 			continue
 		}
@@ -2004,6 +2007,9 @@ func (ev *evaluator) aggregation(op parser.ItemType, grouping []string, without
 			group.groupCount++
 			group.mean += (s.V - group.mean) / float64(group.groupCount)
 
+		case parser.GROUP:
+			// Do nothing. Required to avoid the panic in `default:` below.
+
 		case parser.MAX:
 			if group.value < s.V || math.IsNaN(group.value) {
 				group.value = s.V

promql/parser/generated_parser.y

@@ -92,6 +92,7 @@ AVG
 BOTTOMK
 COUNT
 COUNT_VALUES
+GROUP
 MAX
 MIN
 QUANTILE
@@ -535,7 +536,7 @@ metric          : metric_identifier label_set
                 ;
 
 
-metric_identifier: AVG | BOTTOMK | BY | COUNT | COUNT_VALUES |  IDENTIFIER |  LAND | LOR | LUNLESS | MAX | METRIC_IDENTIFIER | MIN | OFFSET | QUANTILE | STDDEV | STDVAR | SUM | TOPK;
+metric_identifier: AVG | BOTTOMK | BY | COUNT | COUNT_VALUES | GROUP | IDENTIFIER |  LAND | LOR | LUNLESS | MAX | METRIC_IDENTIFIER | MIN | OFFSET | QUANTILE | STDDEV | STDVAR | SUM | TOPK;
 
 label_set       : LEFT_BRACE label_set_list RIGHT_BRACE
                         { $$ = labels.New($2...) }
@@ -635,10 +636,10 @@ series_value    : IDENTIFIER
  * Keyword lists.
  */
 
-aggregate_op    : AVG | BOTTOMK | COUNT | COUNT_VALUES | MAX | MIN | QUANTILE | STDDEV | STDVAR | SUM | TOPK ;
+aggregate_op    : AVG | BOTTOMK | COUNT | COUNT_VALUES | GROUP | MAX | MIN | QUANTILE | STDDEV | STDVAR | SUM | TOPK ;
 
 // inside of grouping options label names can be recognized as keywords by the lexer. This is a list of keywords that could also be a label name.
-maybe_label     : AVG | BOOL | BOTTOMK | BY | COUNT | COUNT_VALUES | GROUP_LEFT | GROUP_RIGHT | IDENTIFIER | IGNORING | LAND | LOR | LUNLESS | MAX | METRIC_IDENTIFIER | MIN | OFFSET | ON | QUANTILE | STDDEV | STDVAR | SUM | TOPK;
+maybe_label     : AVG | BOOL | BOTTOMK | BY | COUNT | COUNT_VALUES | GROUP | GROUP_LEFT | GROUP_RIGHT | IDENTIFIER | IGNORING | LAND | LOR | LUNLESS | MAX | METRIC_IDENTIFIER | MIN | OFFSET | ON | QUANTILE | STDDEV | STDVAR | SUM | TOPK;
 
 unary_op        : ADD | SUB;
 

promql/parser/lex.go

@@ -104,6 +104,7 @@ var key = map[string]ItemType{
 	"count":        COUNT,
 	"min":          MIN,
 	"max":          MAX,
+	"group":        GROUP,
 	"stddev":       STDDEV,
 	"stdvar":       STDVAR,
 	"topk":         TOPK,

promql/parser/lex_test.go

@@ -287,6 +287,9 @@ var tests = []struct {
 			}, {
 				input:    `AVG`,
 				expected: []Item{{AVG, 0, `AVG`}},
+			}, {
+				input:    `GROUP`,
+				expected: []Item{{GROUP, 0, `GROUP`}},
 			}, {
 				input:    `MAX`,
 				expected: []Item{{MAX, 0, `MAX`}},

promql/testdata/aggregators.test

@@ -298,3 +298,25 @@ eval instant at 1m quantile without(point)((scalar(foo)), data)
 	{test="two samples"} 0.8
 	{test="three samples"} 1.6
 	{test="uneven samples"} 2.8
+
+# Tests for group.
+clear
+
+load 10s
+	data{test="two samples",point="a"} 0
+	data{test="two samples",point="b"} 1
+	data{test="three samples",point="a"} 0
+	data{test="three samples",point="b"} 1
+	data{test="three samples",point="c"} 2
+	data{test="uneven samples",point="a"} 0
+	data{test="uneven samples",point="b"} 1
+	data{test="uneven samples",point="c"} 4
+	foo .8
+
+eval instant at 1m group without(point)(data)
+	{test="two samples"} 1
+	{test="three samples"} 1
+	{test="uneven samples"} 1
+
+eval instant at 1m group(foo)
+	{} 1