Resolve "Add support for more features in query builder API"

Closes #39 (closed)

src/query/fns/label.rs

@@ -7,6 +7,15 @@ use crate::query::{
     ops::Operable,
 };
 
+/// MetricsQL's label_set label manipulation query function
+#[inline]
+pub fn mql_label_set<'a>(
+    qry_expr: impl Operable + 'a,
+    label_value_pairs: &'a [&'a str],
+) -> QryFunc<impl Fn(&mut fmt::Formatter) -> fmt::Result + 'a> {
+    basic_label_fn("label_set", qry_expr, label_value_pairs)
+}
+
 /// MetricsQL's label_map query function
 pub fn mql_label_map<'a>(
     qry_expr: impl Operable + 'a,
@@ -111,4 +120,10 @@ mod tests {
             r#"sort_by_label_numeric_desc(metric,"label","label2")"#
         );
     }
+
+    #[test]
+    fn label_label_set() {
+        let qry = mql_label_set(Metric::new("metric"), &["label", "value"]).to_string();
+        assert_eq!(qry, r#"label_set(metric,"label","value")"#);
+    }
 }