Drop selector filters

logicalplan/merge_selects.go

@@ -59,7 +59,16 @@ func replaceMatchers(selectors matcherHeap, expr *parser.Expr) {
 			}
 			// All replacements are done on metrics name only,
 			// so we can drop the explicit metric name selector.
-			filters := dropMetricName(e.LabelMatchers)
+			filters := dropMatcher(labels.MetricName, e.LabelMatchers)
+
+			// Drop filters which are already present as matchers in the replacement selector.
+			for _, s := range replacement {
+				for _, f := range filters {
+					if s.Name == f.Name && s.Value == f.Value && s.Type == f.Type {
+						filters = dropMatcher(f.Name, filters)
+					}
+				}
+			}
 			e.LabelMatchers = replacement
 			*node = &FilteredSelector{
 				Filters:        filters,
@@ -70,9 +79,9 @@ func replaceMatchers(selectors matcherHeap, expr *parser.Expr) {
 	})
 }
 
-func dropMetricName(originalMatchers []*labels.Matcher) []*labels.Matcher {
+func dropMatcher(matcherName string, originalMatchers []*labels.Matcher) []*labels.Matcher {
 	for i, l := range originalMatchers {
-		if l.Name == labels.MetricName {
+		if l.Name == matcherName {
 			originalMatchers = append(originalMatchers[:i], originalMatchers[i+1:]...)
 		}
 	}

logicalplan/plan_test.go

@@ -22,7 +22,7 @@ func TestDefaultOptimizers(t *testing.T) {
 		{
 			name:     "common selectors",
 			expr:     `sum(metric{a="b", c="d"}) / sum(metric{a="b"})`,
-			expected: `sum(filter([a="b" c="d"], metric{a="b"})) / sum(metric{a="b"})`,
+			expected: `sum(filter([c="d"], metric{a="b"})) / sum(metric{a="b"})`,
 		},
 		{
 			name:     "common selectors with regex",
@@ -36,8 +36,8 @@ func TestDefaultOptimizers(t *testing.T) {
 	sum(metric_2{a="b", c="d"}) / sum(metric_2{a="b"})
 `,
 			expected: `
-	sum(filter([a="b" c="d"], metric_1{a="b"})) / sum(metric_1{a="b"}) + 
-	sum(filter([a="b" c="d"], metric_2{a="b"})) / sum(metric_2{a="b"})`,
+	sum(filter([c="d"], metric_1{a="b"})) / sum(metric_1{a="b"}) +
+	sum(filter([c="d"], metric_2{a="b"})) / sum(metric_2{a="b"})`,
 		},
 		{
 			name:     "different selectors",