fix(promql): drop metadata labels from date function results

Prometheus dateWrapper drops __type__ and __unit__ with __name__.

Signed-off-by: Dennis Zhuang <killme2008@gmail.com>

src/promql/src/map_time.rs

@@ -72,7 +72,7 @@ pub fn map_date(
         ));
     };
     let mut metric = series.metric.clone();
-    metric.remove("__name__");
+    metric.remove_all(&METADATA_LABELS);
     let map = |seconds: f64| function.apply(go_int64(seconds));
 
     let all_floats = series.fields.iter().all(|samples| {
@@ -145,6 +145,9 @@ fn go_int64(value: f64) -> i64 {
     }
 }
 
+/// Prometheus `schema.IsMetadataLabel`: the labels removed with the metric name.
+const METADATA_LABELS: [&str; 3] = ["__name__", "__type__", "__unit__"];
+
 const SECONDS_PER_DAY: u64 = 86_400;
 const MARCH_THRU_DECEMBER: u32 = 306;
 const ABSOLUTE_YEARS: u64 = 292_277_022_400;

src/promql/src/map_time/tests.rs

@@ -25,7 +25,7 @@ use datatypes::series::time::{EvalGrid, GridRange, GridSpec, TimeAxis};
 use super::{DateFunction, date_of_eval_time, map_date, time};
 use crate::grid_series::merge_same_labelset;
 use crate::grid_series::reference::{
-    canonical_bits, golden_cases, labels_of, metric_of, points_of, series_of,
+    Labels, canonical_bits, golden_cases, labels_of, metric_of, points_of, series_of,
 };
 
 fn schema(grid: Arc<EvalGrid>) -> Arc<SeriesSchema> {
@@ -108,9 +108,14 @@ fn map_date_drops_histograms_and_maps_chunks() {
         Series::try_new(
             &schema,
             metric_of(
-                &[("__name__", "m"), ("host", "a")]
-                    .map(|(n, v)| (n.into(), v.into()))
-                    .into(),
+                &[
+                    ("__name__", "m"),
+                    ("__type__", "gauge"),
+                    ("__unit__", "seconds"),
+                    ("host", "a"),
+                ]
+                .map(|(n, v)| (n.into(), v.into()))
+                .into(),
             ),
             TimeAxis::Grid(range.clone()),
             SeriesFields::one(fields),
@@ -150,7 +155,10 @@ fn map_date_drops_histograms_and_maps_chunks() {
         points_of(&hours),
         BTreeMap::from([(2, 1f64.to_bits()), (3, 2f64.to_bits())])
     );
-    assert_eq!(hours.metric.name(), None);
+    assert_eq!(
+        labels_of(&hours.metric),
+        Labels::from([("host".into(), "a".into())])
+    );
 
     let chunked = Samples::try_from_chunks(vec![floats(&[60.0]), floats(&[120.0, 180.0])]).unwrap();
     let minutes = map_date(DateFunction::Minute, &schema, &series(chunked))