fix(promql): return no point for zero-interval irate/idelta (#9455)

fix(promql): irate/idelta return no point for a zero-ms sample gap

Signed-off-by: Niladri Adhikary <niladrix719@gmail.com>
(cherry picked from commit 0dde3a7b70)
Signed-off-by: WenyXu <wenymedia@gmail.com>

src/promql/src/functions/idelta.rs

@@ -140,8 +140,13 @@ impl<const IS_RATE: bool> IDelta<IS_RATE> {
 
             let last_offset = ts_offset + last_position;
             let prev_offset = ts_offset + prev_position;
-            let sampled_interval =
-                (ts_values[last_offset] - ts_values[prev_offset]) as f64 / 1000.0;
+            let sampled_interval_ms = ts_values[last_offset] - ts_values[prev_offset];
+            // Sub-millisecond samples round to the same ms; skip instead of dividing by zero.
+            if sampled_interval_ms == 0 {
+                result_builder.append_null();
+                continue;
+            }
+            let sampled_interval = sampled_interval_ms as f64 / 1000.0;
 
             let last_value = value_values[value_offset + last_position];
             let prev_value = value_values[value_offset + prev_position];
@@ -263,4 +268,30 @@ mod test {
             vec![Some(3.0), None, None],
         );
     }
+
+    #[test]
+    fn idelta_skips_samples_in_same_millisecond() {
+        // The last two samples of the first range share 999ms; the second range is 1ms apart.
+        let ts_array = Arc::new(TimestampMillisecondArray::from_iter_values([
+            999i64, 999, 999, 1000,
+        ]));
+        let values_array = Arc::new(Float64Array::from_iter([10.0, 13.0, 999.0, 1000.0]));
+        let ranges = [(0, 3), (2, 2)];
+
+        simple_range_udf_runner(
+            IDelta::<false>::scalar_udf(),
+            RangeArray::from_ranges(ts_array.clone(), ranges).unwrap(),
+            RangeArray::from_ranges(values_array.clone(), ranges).unwrap(),
+            vec![],
+            vec![None, Some(1.0)],
+        );
+
+        simple_range_udf_runner(
+            IDelta::<true>::scalar_udf(),
+            RangeArray::from_ranges(ts_array, ranges).unwrap(),
+            RangeArray::from_ranges(values_array, ranges).unwrap(),
+            vec![],
+            vec![None, Some(1000.0)],
+        );
+    }
 }

tests/cases/standalone/common/promql/sub_millisecond_interval.result

@@ -0,0 +1,77 @@
+-- The last two 'sub_ms' samples are 400ns apart and share one millisecond, which
+-- irate and idelta cannot resolve, so they return no point instead of inf.
+-- The 'one_ms' samples are 1ms apart and still produce a rate.
+CREATE TABLE sub_ms_interval (
+    job STRING,
+    `value` DOUBLE,
+    ts TIMESTAMP(9) TIME INDEX,
+    PRIMARY KEY(job)
+);
+
+Affected Rows: 0
+
+INSERT INTO sub_ms_interval VALUES
+    ('sub_ms', 999, 999999900),
+    ('sub_ms', 10, 999999100),
+    ('sub_ms', 13, 999999500),
+    ('one_ms', 10, 998000000),
+    ('one_ms', 13, 999000000);
+
+Affected Rows: 5
+
+SELECT * FROM sub_ms_interval ORDER BY job, ts;
+
++--------+-------+-------------------------------+
+| job    | value | ts                            |
++--------+-------+-------------------------------+
+| one_ms | 10.0  | 1970-01-01T00:00:00.998       |
+| one_ms | 13.0  | 1970-01-01T00:00:00.999       |
+| sub_ms | 10.0  | 1970-01-01T00:00:00.999999100 |
+| sub_ms | 13.0  | 1970-01-01T00:00:00.999999500 |
+| sub_ms | 999.0 | 1970-01-01T00:00:00.999999900 |
++--------+-------+-------------------------------+
+
+TQL EVAL (1, 1, '1s') irate(sub_ms_interval[5s]);
+
++---------------------+----------------------------+--------+
+| ts                  | prom_irate(ts_range,value) | job    |
++---------------------+----------------------------+--------+
+| 1970-01-01T00:00:01 | 3000.0                     | one_ms |
++---------------------+----------------------------+--------+
+
+TQL EVAL (1, 1, '1s') idelta(sub_ms_interval[5s]);
+
++---------------------+-----------------------------+--------+
+| ts                  | prom_idelta(ts_range,value) | job    |
++---------------------+-----------------------------+--------+
+| 1970-01-01T00:00:01 | 3.0                         | one_ms |
++---------------------+-----------------------------+--------+
+
+ADMIN FLUSH_TABLE('sub_ms_interval');
+
++--------------------------------------+
+| ADMIN FLUSH_TABLE('sub_ms_interval') |
++--------------------------------------+
+| 0                                    |
++--------------------------------------+
+
+TQL EVAL (1, 1, '1s') irate(sub_ms_interval[5s]);
+
++---------------------+----------------------------+--------+
+| ts                  | prom_irate(ts_range,value) | job    |
++---------------------+----------------------------+--------+
+| 1970-01-01T00:00:01 | 3000.0                     | one_ms |
++---------------------+----------------------------+--------+
+
+TQL EVAL (1, 1, '1s') idelta(sub_ms_interval[5s]);
+
++---------------------+-----------------------------+--------+
+| ts                  | prom_idelta(ts_range,value) | job    |
++---------------------+-----------------------------+--------+
+| 1970-01-01T00:00:01 | 3.0                         | one_ms |
++---------------------+-----------------------------+--------+
+
+DROP TABLE sub_ms_interval;
+
+Affected Rows: 0
+

tests/cases/standalone/common/promql/sub_millisecond_interval.sql

@@ -0,0 +1,30 @@
+-- The last two 'sub_ms' samples are 400ns apart and share one millisecond, which
+-- irate and idelta cannot resolve, so they return no point instead of inf.
+-- The 'one_ms' samples are 1ms apart and still produce a rate.
+CREATE TABLE sub_ms_interval (
+    job STRING,
+    `value` DOUBLE,
+    ts TIMESTAMP(9) TIME INDEX,
+    PRIMARY KEY(job)
+);
+
+INSERT INTO sub_ms_interval VALUES
+    ('sub_ms', 999, 999999900),
+    ('sub_ms', 10, 999999100),
+    ('sub_ms', 13, 999999500),
+    ('one_ms', 10, 998000000),
+    ('one_ms', 13, 999000000);
+
+SELECT * FROM sub_ms_interval ORDER BY job, ts;
+
+TQL EVAL (1, 1, '1s') irate(sub_ms_interval[5s]);
+
+TQL EVAL (1, 1, '1s') idelta(sub_ms_interval[5s]);
+
+ADMIN FLUSH_TABLE('sub_ms_interval');
+
+TQL EVAL (1, 1, '1s') irate(sub_ms_interval[5s]);
+
+TQL EVAL (1, 1, '1s') idelta(sub_ms_interval[5s]);
+
+DROP TABLE sub_ms_interval;