From 582dd01f429b737f656990a7f74f6320487b4f83 Mon Sep 17 00:00:00 2001
From: Aliaksandr Valialkin <valyala@gmail.com>
Date: Tue, 21 Jan 2020 19:05:10 +0200
Subject: [PATCH] app/vmselect/promql: add `range_over_time(m[d])` function for
 calculating value range for `m` over `d`

---
 app/vmselect/promql/exec_test.go   | 11 +++++++++++
 app/vmselect/promql/rollup.go      | 11 +++++++++--
 app/vmselect/promql/rollup_test.go |  1 +
 docs/ExtendedPromQL.md             |  1 +
 lib/metricsql/rollup.go            |  1 +
 5 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/app/vmselect/promql/exec_test.go b/app/vmselect/promql/exec_test.go
index 0369ab0e9..f4025997b 100644
--- a/app/vmselect/promql/exec_test.go
+++ b/app/vmselect/promql/exec_test.go
@@ -3248,6 +3248,17 @@ func TestExecSuccess(t *testing.T) {
 		resultExpected := []netstorage.Result{r}
 		f(q, resultExpected)
 	})
+	t.Run(`range_over_time(time)`, func(t *testing.T) {
+		t.Parallel()
+		q := `range_over_time(alias(time()/100, "foobar")[3i])`
+		r := netstorage.Result{
+			MetricName: metricNameExpected,
+			Values:     []float64{4, 4, 4, 4, 4, 4},
+			Timestamps: timestampsExpected,
+		}
+		resultExpected := []netstorage.Result{r}
+		f(q, resultExpected)
+	})
 	t.Run(`sum(multi-vector)`, func(t *testing.T) {
 		t.Parallel()
 		q := `sum(label_set(10, "foo", "bar") or label_set(time()/100, "baz", "sss"))`
diff --git a/app/vmselect/promql/rollup.go b/app/vmselect/promql/rollup.go
index 9bc1bf6c0..563f9dffe 100644
--- a/app/vmselect/promql/rollup.go
+++ b/app/vmselect/promql/rollup.go
@@ -15,8 +15,6 @@ import (
 )
 
 var rollupFuncs = map[string]newRollupFunc{
-	"default_rollup": newRollupFuncOneArg(rollupDefault), // default rollup func
-
 	// Standard rollup funcs from PromQL.
 	// See funcs accepting range-vector on https://prometheus.io/docs/prometheus/latest/querying/functions/ .
 	"changes":            newRollupFuncOneArg(rollupChanges),
@@ -41,6 +39,8 @@ var rollupFuncs = map[string]newRollupFunc{
 	"absent_over_time":   newRollupFuncOneArg(rollupAbsent),
 
 	// Additional rollup funcs.
+	"default_rollup":        newRollupFuncOneArg(rollupDefault), // default rollup func
+	"range_over_time":       newRollupFuncOneArg(rollupRange),
 	"sum2_over_time":        newRollupFuncOneArg(rollupSum2),
 	"geomean_over_time":     newRollupFuncOneArg(rollupGeomean),
 	"first_over_time":       newRollupFuncOneArg(rollupFirst),
@@ -91,6 +91,7 @@ var rollupAggrFuncs = map[string]rollupFunc{
 	"absent_over_time": rollupAbsent,
 
 	// Additional rollup funcs.
+	"range_over_time":     rollupRange,
 	"sum2_over_time":      rollupSum2,
 	"geomean_over_time":   rollupGeomean,
 	"first_over_time":     rollupFirst,
@@ -1052,6 +1053,12 @@ func rollupSum(rfa *rollupFuncArg) float64 {
 	return sum
 }
 
+func rollupRange(rfa *rollupFuncArg) float64 {
+	max := rollupMax(rfa)
+	min := rollupMin(rfa)
+	return max - min
+}
+
 func rollupSum2(rfa *rollupFuncArg) float64 {
 	// There is no need in handling NaNs here, since they must be cleaned up
 	// before calling rollup funcs.
diff --git a/app/vmselect/promql/rollup_test.go b/app/vmselect/promql/rollup_test.go
index f93c917ab..3e506cea9 100644
--- a/app/vmselect/promql/rollup_test.go
+++ b/app/vmselect/promql/rollup_test.go
@@ -370,6 +370,7 @@ func TestRollupNewRollupFuncSuccess(t *testing.T) {
 	f("irate", 0)
 	f("rate", 2200)
 	f("resets", 5)
+	f("range_over_time", 111)
 	f("avg_over_time", 47.083333333333336)
 	f("min_over_time", 12)
 	f("max_over_time", 123)
diff --git a/docs/ExtendedPromQL.md b/docs/ExtendedPromQL.md
index b199e0a8e..f749b4095 100644
--- a/docs/ExtendedPromQL.md
+++ b/docs/ExtendedPromQL.md
@@ -66,6 +66,7 @@ This functionality can be tried at [an editable Grafana dashboard](http://play-g
 - `lifetime(q[d])` - returns lifetime of `q` over `d` in seconds. It is expected that `d` exceeds the lifetime of `q`.
 - `scrape_interval(q[d])` - returns the average interval in seconds between data points of `q` over `d` aka `scrape interval`.
 - Trigonometric functions - `sin(q)`, `cos(q)`, `asin(q)`, `acos(q)` and `pi()`.
+- `range_over_time(m[d])` - returns value range for `m` over `d` time window, i.e. `max_over_time(m[d])-min_over_time(m[d])`.
 - `median_over_time(m[d])` - calculates median values for `m` over `d` time window. Shorthand to `quantile_over_time(0.5, m[d])`.
 - `median(q)` - median aggregate. Shorthand to `quantile(0.5, q)`.
 - `limitk(k, q)` - limits the number of time series returned from `q` to `k`.
diff --git a/lib/metricsql/rollup.go b/lib/metricsql/rollup.go
index 0100d9a02..dbfa223d1 100644
--- a/lib/metricsql/rollup.go
+++ b/lib/metricsql/rollup.go
@@ -30,6 +30,7 @@ var rollupFuncs = map[string]bool{
 
 	// Additional rollup funcs.
 	"default_rollup":        true,
+	"range_over_time":       true,
 	"sum2_over_time":        true,
 	"geomean_over_time":     true,
 	"first_over_time":       true,